]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/kern/kern_event.c
xnu-4570.41.2.tar.gz
[apple/xnu.git] / bsd / kern / kern_event.c
index ba269074ac91fb5abf3b93b41e22bfc83f711fb7..12885133e1b9c755ecc3674bec9e83499843d8ba 100644 (file)
@@ -1,8 +1,8 @@
 /*
- * Copyright (c) 2000-2011 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2017 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
- * 
+ *
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
  * unlawful or unlicensed copies of an Apple operating system, or to
  * circumvent, violate, or enable the circumvention or violation of, any
  * terms of an Apple operating system software license agreement.
- * 
+ *
  * Please obtain a copy of the License at
  * http://www.opensource.apple.com/apsl/ and read it before using this file.
- * 
+ *
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
@@ -22,7 +22,7 @@
  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  * Please see the License for the specific language governing rights and
  * limitations under the License.
- * 
+ *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  *
  */
@@ -55,6 +55,7 @@
  *     @(#)kern_event.c       1.0 (3/31/2000)
  */
 #include <stdint.h>
+#include <stdatomic.h>
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -62,7 +63,7 @@
 #include <sys/kernel.h>
 #include <sys/proc_internal.h>
 #include <sys/kauth.h>
-#include <sys/malloc.h> 
+#include <sys/malloc.h>
 #include <sys/unistd.h>
 #include <sys/file_internal.h>
 #include <sys/fcntl.h>
 #include <sys/vnode_internal.h>
 #include <string.h>
 #include <sys/proc_info.h>
+#include <sys/codesign.h>
+#include <sys/pthread_shims.h>
+#include <sys/kdebug.h>
+#include <sys/reason.h>
+#include <os/reason_private.h>
 
-#include <kern/lock.h>
+#include <kern/locks.h>
 #include <kern/clock.h>
+#include <kern/cpu_data.h>
+#include <kern/policy_internal.h>
 #include <kern/thread_call.h>
 #include <kern/sched_prim.h>
+#include <kern/waitq.h>
 #include <kern/zalloc.h>
+#include <kern/kalloc.h>
 #include <kern/assert.h>
+#include <kern/ast.h>
+#include <kern/thread.h>
+#include <kern/kcdata.h>
 
 #include <libkern/libkern.h>
+#include <libkern/OSAtomic.h>
+
 #include "net/net_str_id.h"
 
 #include <mach/task.h>
+#include <libkern/section_keywords.h>
 
-#if VM_PRESSURE_EVENTS
-#include <kern/vm_pressure.h>
+#if CONFIG_MEMORYSTATUS
+#include <sys/kern_memorystatus.h>
 #endif
 
+extern thread_t        port_name_to_thread(mach_port_name_t    port_name); /* osfmk/kern/ipc_tt.h   */
+extern mach_port_name_t ipc_entry_name_mask(mach_port_name_t name); /* osfmk/ipc/ipc_entry.h */
+
+#define KEV_EVTID(code) BSDDBG_CODE(DBG_BSD_KEVENT, (code))
+
+/*
+ * JMM - this typedef needs to be unified with pthread_priority_t
+ *       and mach_msg_priority_t. It also needs to be the same type
+ *       everywhere.
+ */
+typedef int32_t qos_t;
+
 MALLOC_DEFINE(M_KQUEUE, "kqueue", "memory for kqueue system");
 
-#define KQ_EVENT NULL
-
-static inline void kqlock(struct kqueue *kq);
-static inline void kqunlock(struct kqueue *kq);
-
-static int     kqlock2knoteuse(struct kqueue *kq, struct knote *kn);
-static int     kqlock2knoteusewait(struct kqueue *kq, struct knote *kn);
-static int     kqlock2knotedrop(struct kqueue *kq, struct knote *kn);
-static int     knoteuse2kqlock(struct kqueue *kq, struct knote *kn);
-
-static void    kqueue_wakeup(struct kqueue *kq, int closed);
-static int     kqueue_read(struct fileproc *fp, struct uio *uio,
-                   int flags, vfs_context_t ctx);
-static int     kqueue_write(struct fileproc *fp, struct uio *uio,
-                   int flags, vfs_context_t ctx);
-static int     kqueue_ioctl(struct fileproc *fp, u_long com, caddr_t data,
-                   vfs_context_t ctx);
-static int     kqueue_select(struct fileproc *fp, int which, void *wql, 
-                   vfs_context_t ctx);
-static int     kqueue_close(struct fileglob *fg, vfs_context_t ctx);
-static int     kqueue_kqfilter(struct fileproc *fp, struct knote *kn, vfs_context_t ctx);
-static int     kqueue_drain(struct fileproc *fp, vfs_context_t ctx);
-extern int     kqueue_stat(struct fileproc *fp, void  *ub, int isstat64, vfs_context_t ctx);
-
-static struct fileops kqueueops = {
-       .fo_read = kqueue_read,
-       .fo_write = kqueue_write,
-       .fo_ioctl = kqueue_ioctl,
-       .fo_select = kqueue_select,
-       .fo_close = kqueue_close,
-       .fo_kqfilter = kqueue_kqfilter,
+#define        KQ_EVENT        NO_EVENT64
+
+#define KNUSE_NONE       0x0
+#define KNUSE_STEAL_DROP 0x1
+#define KNUSE_BOOST      0x2
+static int kqlock2knoteuse(struct kqueue *kq, struct knote *kn, int flags);
+static int kqlock2knotedrop(struct kqueue *kq, struct knote *kn);
+static int kqlock2knotedetach(struct kqueue *kq, struct knote *kn, int flags);
+static int knoteuse2kqlock(struct kqueue *kq, struct knote *kn, int flags);
+
+static int kqueue_read(struct fileproc *fp, struct uio *uio,
+               int flags, vfs_context_t ctx);
+static int kqueue_write(struct fileproc *fp, struct uio *uio,
+               int flags, vfs_context_t ctx);
+static int kqueue_ioctl(struct fileproc *fp, u_long com, caddr_t data,
+               vfs_context_t ctx);
+static int kqueue_select(struct fileproc *fp, int which, void *wq_link_id,
+               vfs_context_t ctx);
+static int kqueue_close(struct fileglob *fg, vfs_context_t ctx);
+static int kqueue_kqfilter(struct fileproc *fp, struct knote *kn,
+               struct kevent_internal_s *kev, vfs_context_t ctx);
+static int kqueue_drain(struct fileproc *fp, vfs_context_t ctx);
+
+static const struct fileops kqueueops = {
+       .fo_type = DTYPE_KQUEUE,
+       .fo_read = kqueue_read,
+       .fo_write = kqueue_write,
+       .fo_ioctl = kqueue_ioctl,
+       .fo_select = kqueue_select,
+       .fo_close = kqueue_close,
+       .fo_kqfilter = kqueue_kqfilter,
        .fo_drain = kqueue_drain,
 };
 
-static int kevent_internal(struct proc *p, int iskev64, user_addr_t changelist,
-               int nchanges, user_addr_t eventlist, int nevents, int fd, 
-               user_addr_t utimeout, unsigned int flags, int32_t *retval);
-static int kevent_copyin(user_addr_t *addrp, struct kevent64_s *kevp, struct proc *p, int iskev64);
-static int kevent_copyout(struct kevent64_s *kevp, user_addr_t *addrp, struct proc *p, int iskev64);
-char * kevent_description(struct kevent64_s *kevp, char *s, size_t n);
-
-static int     kevent_callback(struct kqueue *kq, struct kevent64_s *kevp, void *data);
-static void    kevent_continue(struct kqueue *kq, void *data, int error);
-static void    kqueue_scan_continue(void *contp, wait_result_t wait_result);
-static int     kqueue_process(struct kqueue *kq, kevent_callback_t callback,
-                              void *data, int *countp, struct proc *p);
-static int     kqueue_begin_processing(struct kqueue *kq);
-static void    kqueue_end_processing(struct kqueue *kq);
-static int     knote_process(struct knote *kn, kevent_callback_t callback,
-                             void *data, struct kqtailq *inprocessp, struct proc *p);
-static void    knote_put(struct knote *kn);
-static int     knote_fdpattach(struct knote *kn, struct filedesc *fdp, struct proc *p);
-static void    knote_drop(struct knote *kn, struct proc *p);
-static void    knote_activate(struct knote *kn, int);
-static void    knote_deactivate(struct knote *kn);
-static void    knote_enqueue(struct knote *kn);
-static void    knote_dequeue(struct knote *kn);
-static struct  knote *knote_alloc(void);
-static void    knote_free(struct knote *kn);
-
-static int     filt_fileattach(struct knote *kn);
-static struct filterops file_filtops = {
-        .f_isfd = 1,
-        .f_attach = filt_fileattach,
+static void kevent_put_kq(struct proc *p, kqueue_id_t id, struct fileproc *fp, struct kqueue *kq);
+static int kevent_internal(struct proc *p,
+                          kqueue_id_t id, kqueue_id_t *id_out,
+                          user_addr_t changelist, int nchanges,
+                          user_addr_t eventlist, int nevents, 
+                          user_addr_t data_out, uint64_t data_available,
+                          unsigned int flags, user_addr_t utimeout,
+                          kqueue_continue_t continuation,
+                          int32_t *retval);
+static int kevent_copyin(user_addr_t *addrp, struct kevent_internal_s *kevp,
+                        struct proc *p, unsigned int flags);
+static int kevent_copyout(struct kevent_internal_s *kevp, user_addr_t *addrp,
+                         struct proc *p, unsigned int flags);
+char * kevent_description(struct kevent_internal_s *kevp, char *s, size_t n);
+
+static void kqueue_interrupt(struct kqueue *kq);
+static int kevent_callback(struct kqueue *kq, struct kevent_internal_s *kevp,
+                          void *data);
+static void kevent_continue(struct kqueue *kq, void *data, int error);
+static void kqueue_scan_continue(void *contp, wait_result_t wait_result);
+static int kqueue_process(struct kqueue *kq, kevent_callback_t callback, void *callback_data,
+                          struct filt_process_s *process_data, int *countp, struct proc *p);
+static struct kqtailq *kqueue_get_base_queue(struct kqueue *kq, kq_index_t qos_index);
+static struct kqtailq *kqueue_get_high_queue(struct kqueue *kq, kq_index_t qos_index);
+static int kqueue_queue_empty(struct kqueue *kq, kq_index_t qos_index);
+
+static struct kqtailq *kqueue_get_suppressed_queue(struct kqueue *kq, kq_index_t qos_index);
+
+static void kqworkq_request_thread(struct kqworkq *kqwq, kq_index_t qos_index);
+static void kqworkq_request_help(struct kqworkq *kqwq, kq_index_t qos_index);
+static void kqworkq_update_override(struct kqworkq *kqwq, kq_index_t qos_index, kq_index_t override_index);
+static void kqworkq_bind_thread_impl(struct kqworkq *kqwq, kq_index_t qos_index, thread_t thread, unsigned int flags);
+static void kqworkq_unbind_thread(struct kqworkq *kqwq, kq_index_t qos_index, thread_t thread, unsigned int flags);
+static struct kqrequest *kqworkq_get_request(struct kqworkq *kqwq, kq_index_t qos_index);
+
+enum {
+       KQWL_UO_NONE = 0,
+       KQWL_UO_OLD_OVERRIDE_IS_SYNC_UI = 0x1,
+       KQWL_UO_NEW_OVERRIDE_IS_SYNC_UI = 0x2,
+       KQWL_UO_UPDATE_SUPPRESS_SYNC_COUNTERS = 0x4,
+       KQWL_UO_UPDATE_OVERRIDE_LAZY = 0x8
 };
 
-static void    filt_kqdetach(struct knote *kn);
-static int     filt_kqueue(struct knote *kn, long hint);
-static struct filterops kqread_filtops = {
-        .f_isfd = 1,
-        .f_detach = filt_kqdetach,
-        .f_event = filt_kqueue,
+static void kqworkloop_update_override(struct kqworkloop *kqwl, kq_index_t qos_index, kq_index_t override_index, uint32_t flags);
+static void kqworkloop_bind_thread_impl(struct kqworkloop *kqwl, thread_t thread, unsigned int flags);
+static void kqworkloop_unbind_thread(struct kqworkloop *kqwl, thread_t thread, unsigned int flags);
+static inline kq_index_t kqworkloop_combined_qos(struct kqworkloop *kqwl, boolean_t *);
+static void kqworkloop_update_suppress_sync_count(struct kqrequest *kqr, uint32_t flags);
+enum {
+       KQWL_UTQ_NONE,
+       /*
+        * The wakeup qos is the qos of QUEUED knotes.
+        *
+        * This QoS is accounted for with the events override in the
+        * kqr_override_index field. It is raised each time a new knote is queued at
+        * a given QoS. The kqr_wakeup_indexes field is a superset of the non empty
+        * knote buckets and is recomputed after each event delivery.
+        */
+       KQWL_UTQ_UPDATE_WAKEUP_QOS,
+       KQWL_UTQ_UPDATE_STAYACTIVE_QOS,
+       KQWL_UTQ_RECOMPUTE_WAKEUP_QOS,
+       /*
+        * The wakeup override is for suppressed knotes that have fired again at
+        * a higher QoS than the one for which they are suppressed already.
+        * This override is cleared when the knote suppressed list becomes empty.
+        */
+       KQWL_UTQ_UPDATE_WAKEUP_OVERRIDE,
+       KQWL_UTQ_RESET_WAKEUP_OVERRIDE,
+       /*
+        * The async QoS is the maximum QoS of an event enqueued on this workloop in
+        * userland. It is copied from the only EVFILT_WORKLOOP knote with
+        * a NOTE_WL_THREAD_REQUEST bit set allowed on this workloop. If there is no
+        * such knote, this QoS is 0.
+        */
+       KQWL_UTQ_SET_ASYNC_QOS,
+       /*
+        * The sync waiters QoS is the maximum QoS of any thread blocked on an
+        * EVFILT_WORKLOOP knote marked with the NOTE_WL_SYNC_WAIT bit.
+        * If there is no such knote, this QoS is 0.
+        */
+       KQWL_UTQ_SET_SYNC_WAITERS_QOS,
+       KQWL_UTQ_REDRIVE_EVENTS,
 };
+static void kqworkloop_update_threads_qos(struct kqworkloop *kqwl, int op, kq_index_t qos);
+static void kqworkloop_request_help(struct kqworkloop *kqwl, kq_index_t qos_index);
 
-/*
- * placeholder for not-yet-implemented filters
- */ 
-static int     filt_badattach(struct knote *kn);
-static struct filterops bad_filtops = {
-        .f_attach = filt_badattach,
-};
+static int knote_process(struct knote *kn, kevent_callback_t callback, void *callback_data,
+                        struct filt_process_s *process_data, struct proc *p);
+#if 0
+static void knote_put(struct knote *kn);
+#endif
 
-static int     filt_procattach(struct knote *kn);
-static void    filt_procdetach(struct knote *kn);
-static int     filt_proc(struct knote *kn, long hint);
-static struct filterops proc_filtops = {
-        .f_attach = filt_procattach,
-        .f_detach = filt_procdetach,
-        .f_event = filt_proc,
+static int kq_add_knote(struct kqueue *kq, struct knote *kn,
+               struct kevent_internal_s *kev, struct proc *p, int *knoteuse_flags);
+static struct knote *kq_find_knote_and_kq_lock(struct kqueue *kq, struct kevent_internal_s *kev, bool is_fd, struct proc *p);
+static void kq_remove_knote(struct kqueue *kq, struct knote *kn, struct proc *p, kn_status_t *kn_status, uint16_t *kq_state);
+
+static void knote_drop(struct knote *kn, struct proc *p);
+static struct knote *knote_alloc(void);
+static void knote_free(struct knote *kn);
+
+static void knote_activate(struct knote *kn);
+static void knote_deactivate(struct knote *kn);
+
+static void knote_enable(struct knote *kn);
+static void knote_disable(struct knote *kn);
+
+static int knote_enqueue(struct knote *kn);
+static void knote_dequeue(struct knote *kn);
+
+static void knote_suppress(struct knote *kn);
+static void knote_unsuppress(struct knote *kn);
+static void knote_wakeup(struct knote *kn);
+
+static kq_index_t knote_get_queue_index(struct knote *kn);
+static struct kqtailq *knote_get_queue(struct knote *kn);
+static kq_index_t knote_get_req_index(struct knote *kn);
+static kq_index_t knote_get_qos_index(struct knote *kn);
+static void knote_set_qos_index(struct knote *kn, kq_index_t qos_index);
+static kq_index_t knote_get_qos_override_index(struct knote *kn);
+static kq_index_t knote_get_sync_qos_override_index(struct knote *kn);
+static void knote_set_qos_override_index(struct knote *kn, kq_index_t qos_index, boolean_t override_is_sync);
+static void knote_set_qos_overcommit(struct knote *kn);
+
+static int filt_fileattach(struct knote *kn, struct kevent_internal_s *kev);
+SECURITY_READ_ONLY_EARLY(static struct filterops) file_filtops = {
+       .f_isfd = 1,
+       .f_attach = filt_fileattach,
 };
 
-#if VM_PRESSURE_EVENTS
-static int filt_vmattach(struct knote *kn);
-static void filt_vmdetach(struct knote *kn);
-static int filt_vm(struct knote *kn, long hint);
-static struct filterops vm_filtops = {
-       .f_attach = filt_vmattach,
-       .f_detach = filt_vmdetach,
-       .f_event = filt_vm,
-};
-#endif /* VM_PRESSURE_EVENTS */
-
-extern struct filterops fs_filtops;
-
-extern struct filterops sig_filtops;
-
-/* Timer filter */
-static int     filt_timerattach(struct knote *kn);
-static void    filt_timerdetach(struct knote *kn);
-static int     filt_timer(struct knote *kn, long hint);
-static void     filt_timertouch(struct knote *kn, struct kevent64_s *kev, 
-               long type);
-static struct filterops timer_filtops = {
-        .f_attach = filt_timerattach,
-        .f_detach = filt_timerdetach,
-        .f_event = filt_timer,
-        .f_touch = filt_timertouch,
+static void filt_kqdetach(struct knote *kn);
+static int filt_kqueue(struct knote *kn, long hint);
+static int filt_kqtouch(struct knote *kn, struct kevent_internal_s *kev);
+static int filt_kqprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev);
+SECURITY_READ_ONLY_EARLY(static struct filterops) kqread_filtops = {
+       .f_isfd = 1,
+       .f_detach = filt_kqdetach,
+       .f_event = filt_kqueue,
+       .f_touch = filt_kqtouch,
+       .f_process = filt_kqprocess,
 };
 
-/* Helpers */
+/* placeholder for not-yet-implemented filters */
+static int filt_badattach(struct knote *kn, struct kevent_internal_s *kev);
+SECURITY_READ_ONLY_EARLY(static struct filterops) bad_filtops = {
+       .f_attach = filt_badattach,
+};
 
-static void    filt_timerexpire(void *knx, void *param1);
-static int     filt_timervalidate(struct knote *kn);
-static void    filt_timerupdate(struct knote *kn);
-static void    filt_timercancel(struct knote *kn);
+static int filt_procattach(struct knote *kn, struct kevent_internal_s *kev);
+static void filt_procdetach(struct knote *kn);
+static int filt_proc(struct knote *kn, long hint);
+static int filt_proctouch(struct knote *kn, struct kevent_internal_s *kev);
+static int filt_procprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev);
+SECURITY_READ_ONLY_EARLY(static struct filterops) proc_filtops = {
+       .f_attach = filt_procattach,
+       .f_detach = filt_procdetach,
+       .f_event = filt_proc,
+       .f_touch = filt_proctouch,
+       .f_process = filt_procprocess,
+};
 
-#define TIMER_RUNNING          0x1
-#define TIMER_CANCELWAIT       0x2
+#if CONFIG_MEMORYSTATUS
+extern const struct filterops memorystatus_filtops;
+#endif /* CONFIG_MEMORYSTATUS */
 
-static lck_mtx_t _filt_timerlock;
-static void    filt_timerlock(void);
-static void    filt_timerunlock(void);
+extern const struct filterops fs_filtops;
 
-static zone_t  knote_zone;
+extern const struct filterops sig_filtops;
 
-#define KN_HASH(val, mask)     (((val) ^ (val >> 8)) & (mask))
+static zone_t knote_zone;
+static zone_t kqfile_zone;
+static zone_t kqworkq_zone;
+static zone_t kqworkloop_zone;
 
-#if 0
-extern struct filterops aio_filtops;
-#endif
+#define        KN_HASH(val, mask)      (((val) ^ (val >> 8)) & (mask))
 
 /* Mach portset filter */
-extern struct filterops machport_filtops;
+extern const struct filterops machport_filtops;
 
 /* User filter */
-static int      filt_userattach(struct knote *kn);
-static void    filt_userdetach(struct knote *kn);
-static int     filt_user(struct knote *kn, long hint);
-static void     filt_usertouch(struct knote *kn, struct kevent64_s *kev, 
-               long type);
-static struct filterops user_filtops = {
-        .f_attach = filt_userattach,
-        .f_detach = filt_userdetach,
-        .f_event = filt_user,
-        .f_touch = filt_usertouch,
+static int filt_userattach(struct knote *kn, struct kevent_internal_s *kev);
+static void filt_userdetach(struct knote *kn);
+static int filt_user(struct knote *kn, long hint);
+static int filt_usertouch(struct knote *kn, struct kevent_internal_s *kev);
+static int filt_userprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev);
+SECURITY_READ_ONLY_EARLY(static struct filterops) user_filtops = {
+       .f_attach = filt_userattach,
+       .f_detach = filt_userdetach,
+       .f_event = filt_user,
+       .f_touch = filt_usertouch,
+       .f_process = filt_userprocess,
+};
+
+static lck_spin_t _filt_userlock;
+static void filt_userlock(void);
+static void filt_userunlock(void);
+
+/* Workloop filter */
+static bool filt_wlneeds_boost(struct kevent_internal_s *kev);
+static int filt_wlattach(struct knote *kn, struct kevent_internal_s *kev);
+static int filt_wlpost_attach(struct knote *kn, struct  kevent_internal_s *kev);
+static void filt_wldetach(struct knote *kn);
+static int filt_wlevent(struct knote *kn, long hint);
+static int filt_wltouch(struct knote *kn, struct kevent_internal_s *kev);
+static int filt_wldrop_and_unlock(struct knote *kn, struct kevent_internal_s *kev);
+static int filt_wlprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev);
+SECURITY_READ_ONLY_EARLY(static struct filterops) workloop_filtops = {
+       .f_needs_boost = filt_wlneeds_boost,
+       .f_attach = filt_wlattach,
+       .f_post_attach = filt_wlpost_attach,
+       .f_detach = filt_wldetach,
+       .f_event = filt_wlevent,
+       .f_touch = filt_wltouch,
+       .f_drop_and_unlock = filt_wldrop_and_unlock,
+       .f_process = filt_wlprocess,
 };
 
+extern const struct filterops pipe_rfiltops;
+extern const struct filterops pipe_wfiltops;
+extern const struct filterops ptsd_kqops;
+extern const struct filterops ptmx_kqops;
+extern const struct filterops soread_filtops;
+extern const struct filterops sowrite_filtops;
+extern const struct filterops sock_filtops;
+extern const struct filterops soexcept_filtops;
+extern const struct filterops spec_filtops;
+extern const struct filterops bpfread_filtops;
+extern const struct filterops necp_fd_rfiltops;
+extern const struct filterops fsevent_filtops;
+extern const struct filterops vnode_filtops;
+extern const struct filterops tty_filtops;
+
+const static struct filterops timer_filtops;
+
 /*
- * Table for for all system-defined filters.
+ *
+ * Rules for adding new filters to the system:
+ * Public filters:
+ * - Add a new "EVFILT_" option value to bsd/sys/event.h (typically a negative value)
+ *   in the exported section of the header
+ * - Update the EVFILT_SYSCOUNT value to reflect the new addition
+ * - Add a filterops to the sysfilt_ops array. Public filters should be added at the end 
+ *   of the Public Filters section in the array.
+ * Private filters:
+ * - Add a new "EVFILT_" value to bsd/sys/event.h (typically a positive value)
+ *   in the XNU_KERNEL_PRIVATE section of the header
+ * - Update the EVFILTID_MAX value to reflect the new addition
+ * - Add a filterops to the sysfilt_ops. Private filters should be added at the end of 
+ *   the Private filters section of the array. 
  */
-static struct filterops *sysfilt_ops[] = {
-       &file_filtops,                  /* EVFILT_READ */
-       &file_filtops,                  /* EVFILT_WRITE */
-#if 0
-       &aio_filtops,                   /* EVFILT_AIO */
-#else
-       &bad_filtops,                   /* EVFILT_AIO */
-#endif
-       &file_filtops,                  /* EVFILT_VNODE */
-       &proc_filtops,                  /* EVFILT_PROC */
-       &sig_filtops,                   /* EVFILT_SIGNAL */
-       &timer_filtops,                 /* EVFILT_TIMER */
-       &machport_filtops,              /* EVFILT_MACHPORT */
-       &fs_filtops,                    /* EVFILT_FS */
-       &user_filtops,                  /* EVFILT_USER */
-       &bad_filtops,                   /* unused */
-#if VM_PRESSURE_EVENTS
-       &vm_filtops,                    /* EVFILT_VM */
+SECURITY_READ_ONLY_EARLY(static struct filterops *) sysfilt_ops[EVFILTID_MAX] = {
+       /* Public Filters */
+       [~EVFILT_READ]                                  = &file_filtops,
+       [~EVFILT_WRITE]                                 = &file_filtops,
+       [~EVFILT_AIO]                                   = &bad_filtops,
+       [~EVFILT_VNODE]                                 = &file_filtops,
+       [~EVFILT_PROC]                                  = &proc_filtops,
+       [~EVFILT_SIGNAL]                                = &sig_filtops,
+       [~EVFILT_TIMER]                                 = &timer_filtops,
+       [~EVFILT_MACHPORT]                              = &machport_filtops,
+       [~EVFILT_FS]                                    = &fs_filtops,
+       [~EVFILT_USER]                                  = &user_filtops,
+                                                                         &bad_filtops,
+                                                                         &bad_filtops,
+       [~EVFILT_SOCK]                                  = &file_filtops,
+#if CONFIG_MEMORYSTATUS
+       [~EVFILT_MEMORYSTATUS]                  = &memorystatus_filtops,
 #else
-       &bad_filtops,                   /* EVFILT_VM */
+       [~EVFILT_MEMORYSTATUS]                  = &bad_filtops,
 #endif
-       &file_filtops,                  /* EVFILT_SOCK */
+       [~EVFILT_EXCEPT]                                = &file_filtops,
+
+       [~EVFILT_WORKLOOP]              = &workloop_filtops,
+
+       /* Private filters */
+       [EVFILTID_KQREAD]                               = &kqread_filtops,
+       [EVFILTID_PIPE_R]                               = &pipe_rfiltops,
+       [EVFILTID_PIPE_W]                               = &pipe_wfiltops,
+       [EVFILTID_PTSD]                                 = &ptsd_kqops,
+       [EVFILTID_SOREAD]                               = &soread_filtops,
+       [EVFILTID_SOWRITE]                              = &sowrite_filtops,
+       [EVFILTID_SCK]                                  = &sock_filtops,
+       [EVFILTID_SOEXCEPT]                     = &soexcept_filtops,
+       [EVFILTID_SPEC]                                 = &spec_filtops,
+       [EVFILTID_BPFREAD]                              = &bpfread_filtops,
+       [EVFILTID_NECP_FD]                              = &necp_fd_rfiltops,
+       [EVFILTID_FSEVENT]                              = &fsevent_filtops,
+       [EVFILTID_VN]                                   = &vnode_filtops,
+       [EVFILTID_TTY]                                  = &tty_filtops,
+       [EVFILTID_PTMX]                                 = &ptmx_kqops,
 };
 
+/* waitq prepost callback */
+void waitq_set__CALLING_PREPOST_HOOK__(void *kq_hook, void *knote_hook, int qos);
+
+#ifndef _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG
+#define _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG 0x02000000 /* pthread event manager bit */
+#endif
+#ifndef _PTHREAD_PRIORITY_OVERCOMMIT_FLAG
+#define _PTHREAD_PRIORITY_OVERCOMMIT_FLAG    0x80000000 /* request overcommit threads */
+#endif
+#ifndef _PTHREAD_PRIORITY_QOS_CLASS_MASK
+#define _PTHREAD_PRIORITY_QOS_CLASS_MASK    0x003fff00  /* QoS class mask */
+#endif
+#ifndef _PTHREAD_PRIORITY_QOS_CLASS_SHIFT_32
+#define _PTHREAD_PRIORITY_QOS_CLASS_SHIFT_32 8
+#endif
+
+static inline __kdebug_only
+uintptr_t
+kqr_thread_id(struct kqrequest *kqr)
+{
+       return (uintptr_t)thread_tid(kqr->kqr_thread);
+}
+
+static inline
+boolean_t is_workqueue_thread(thread_t thread)
+{
+       return (thread_get_tag(thread) & THREAD_TAG_WORKQUEUE);
+}
+
+static inline
+void knote_canonicalize_kevent_qos(struct knote *kn)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       unsigned long canonical;
+
+       if ((kq->kq_state & (KQ_WORKQ | KQ_WORKLOOP)) == 0)
+               return;
+
+       /* preserve manager and overcommit flags in this case */
+       canonical = pthread_priority_canonicalize(kn->kn_qos, FALSE);
+       kn->kn_qos = (qos_t)canonical;
+}
+
+static inline
+kq_index_t qos_index_from_qos(struct knote *kn, qos_t qos, boolean_t propagation)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       kq_index_t qos_index;
+       unsigned long flags = 0;
+
+       if ((kq->kq_state & (KQ_WORKQ | KQ_WORKLOOP)) == 0)
+               return QOS_INDEX_KQFILE;
+
+       qos_index = (kq_index_t)thread_qos_from_pthread_priority(
+                               (unsigned long)qos, &flags);
+       
+       if (kq->kq_state & KQ_WORKQ) {
+               /* workq kqueues support requesting a manager thread (non-propagation) */
+               if (!propagation && (flags & _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG))
+                       return KQWQ_QOS_MANAGER;
+       }
+
+       return qos_index;
+}
+
+static inline
+qos_t qos_from_qos_index(kq_index_t qos_index)
+{
+       /* should only happen for KQ_WORKQ */
+       if (qos_index == KQWQ_QOS_MANAGER) 
+               return  _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
+
+       if (qos_index == 0)
+               return THREAD_QOS_UNSPECIFIED;
+
+       /* Should have support from pthread kext support */
+       return (1 << (qos_index - 1 + 
+                     _PTHREAD_PRIORITY_QOS_CLASS_SHIFT_32));
+}
+
+/* kqr lock must be held */
+static inline
+unsigned long pthread_priority_for_kqrequest(
+       struct kqrequest *kqr,
+       kq_index_t qos_index)
+{
+       unsigned long priority = qos_from_qos_index(qos_index);
+       if (kqr->kqr_state & KQR_THOVERCOMMIT) {
+               priority |= _PTHREAD_PRIORITY_OVERCOMMIT_FLAG;
+       }
+       return priority;
+}
+
+static inline
+kq_index_t qos_index_for_servicer(int qos_class, thread_t thread, int flags)
+{
+#pragma unused(thread)
+       kq_index_t qos_index;
+
+       if (flags & KEVENT_FLAG_WORKQ_MANAGER)
+               return KQWQ_QOS_MANAGER;
+
+       qos_index = (kq_index_t)qos_class;
+       assert(qos_index > 0 && qos_index < KQWQ_QOS_MANAGER);
+
+       return qos_index;
+}
+
 /*
- * kqueue/note lock attributes and implementations
+ * kqueue/note lock implementations
+ *
+ *     The kqueue lock guards the kq state, the state of its queues,
+ *     and the kqueue-aware status and use counts of individual knotes.
+ *
+ *     The kqueue workq lock is used to protect state guarding the
+ *     interaction of the kqueue with the workq.  This state cannot
+ *     be guarded by the kq lock - as it needs to be taken when we
+ *     already have the waitq set lock held (during the waitq hook
+ *     callback).  It might be better to use the waitq lock itself
+ *     for this, but the IRQ requirements make that difficult).
  *
- *     kqueues have locks, while knotes have use counts
- *     Most of the knote state is guarded by the object lock.
- *     the knote "inuse" count and status use the kqueue lock.
+ *     Knote flags, filter flags, and associated data are protected
+ *     by the underlying object lock - and are only ever looked at
+ *     by calling the filter to get a [consistent] snapshot of that
+ *     data.
  */
 lck_grp_attr_t * kq_lck_grp_attr;
 lck_grp_t * kq_lck_grp;
@@ -301,94 +590,203 @@ kqlock(struct kqueue *kq)
        lck_spin_lock(&kq->kq_lock);
 }
 
+static inline void
+kqlock_held(__assert_only struct kqueue *kq)
+{
+       LCK_SPIN_ASSERT(&kq->kq_lock, LCK_ASSERT_OWNED);
+}
+
 static inline void
 kqunlock(struct kqueue *kq)
 {
        lck_spin_unlock(&kq->kq_lock);
 }
 
-/* 
+static inline void
+knhash_lock(proc_t p)
+{
+       lck_mtx_lock(&p->p_fd->fd_knhashlock);
+}
+
+static inline void
+knhash_unlock(proc_t p)
+{
+       lck_mtx_unlock(&p->p_fd->fd_knhashlock);
+}
+
+
+/*
  * Convert a kq lock to a knote use referece.
  *
- *     If the knote is being dropped, we can't get
- *     a use reference, so just return with it
- *     still locked.
- *     
+ *     If the knote is being dropped, or has
+ *  vanished, we can't get a use reference.
+ *  Just return with it still locked.
+ *
  *     - kq locked at entry
  *     - unlock on exit if we get the use reference
  */
 static int
-kqlock2knoteuse(struct kqueue *kq, struct knote *kn)
+kqlock2knoteuse(struct kqueue *kq, struct knote *kn, int flags)
 {
-       if (kn->kn_status & KN_DROPPING)
-               return 0;
+       if (kn->kn_status & (KN_DROPPING | KN_VANISHED))
+               return (0);
+
+       assert(kn->kn_status & KN_ATTACHED);
        kn->kn_inuse++;
+       if (flags & KNUSE_BOOST) {
+               set_thread_rwlock_boost();
+       }
        kqunlock(kq);
-       return 1;
- }
+       return (1);
+}
 
-/* 
- * Convert a kq lock to a knote use referece,
- * but wait for attach and drop events to complete.
- *
- *     If the knote is being dropped, we can't get
- *     a use reference, so just return with it
- *     still locked.
- *     
+/*
  *     - kq locked at entry
- *     - kq always unlocked on exit
+ *     - kq unlocked at exit
  */
-static int
-kqlock2knoteusewait(struct kqueue *kq, struct knote *kn)
+__disable_tail_calls
+static wait_result_t
+knoteusewait(struct kqueue *kq, struct knote *kn)
 {
-       if ((kn->kn_status & (KN_DROPPING | KN_ATTACHING)) != 0) {
-               kn->kn_status |= KN_USEWAIT;
-               wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_UNINT, 0);
-               kqunlock(kq);
-               thread_block(THREAD_CONTINUE_NULL);
-               return 0;
-       }
-       kn->kn_inuse++;
+       kn->kn_status |= KN_USEWAIT;
+       waitq_assert_wait64((struct waitq *)&kq->kq_wqs,
+                       CAST_EVENT64_T(&kn->kn_status),
+                       THREAD_UNINT, TIMEOUT_WAIT_FOREVER);
        kqunlock(kq);
-       return 1;
- }
+       return thread_block(THREAD_CONTINUE_NULL);
+}
 
+static bool
+knoteuse_needs_boost(struct knote *kn, struct kevent_internal_s *kev)
+{
+       if (knote_fops(kn)->f_needs_boost) {
+               return knote_fops(kn)->f_needs_boost(kev);
+       }
+       return false;
+}
 
-/* 
+/*
  * Convert from a knote use reference back to kq lock.
  *
  *     Drop a use reference and wake any waiters if
  *     this is the last one.
  *
- *     The exit return indicates if the knote is
- *     still alive - but the kqueue lock is taken
- *     unconditionally.
+ *  If someone is trying to drop the knote, but the
+ *  caller has events they must deliver, take
+ *  responsibility for the drop later - and wake the
+ *  other attempted dropper in a manner that informs
+ *  him of the transfer of responsibility.
+ *
+ *     The exit return indicates if the knote is still alive
+ *  (or if not, the other dropper has been given the green
+ *  light to drop it).
+ *
+ *  The kqueue lock is re-taken unconditionally.
  */
 static int
-knoteuse2kqlock(struct kqueue *kq, struct knote *kn)
+knoteuse2kqlock(struct kqueue *kq, struct knote *kn, int flags)
 {
+       int dropped = 0;
+       int steal_drop = (flags & KNUSE_STEAL_DROP);
+
        kqlock(kq);
+       if (flags & KNUSE_BOOST) {
+               clear_thread_rwlock_boost();
+       }
+
        if (--kn->kn_inuse == 0) {
+
                if ((kn->kn_status & KN_ATTACHING) != 0) {
                        kn->kn_status &= ~KN_ATTACHING;
                }
+
                if ((kn->kn_status & KN_USEWAIT) != 0) {
+                       wait_result_t result;
+
+                       /* If we need to, try and steal the drop */
+                       if (kn->kn_status & KN_DROPPING) {
+                               if (steal_drop && !(kn->kn_status & KN_STOLENDROP)) {
+                                       kn->kn_status |= KN_STOLENDROP;
+                               } else {
+                                       dropped = 1;
+                               }
+                       }
+
+                       /* wakeup indicating if ANY USE stole the drop */
+                       result = (kn->kn_status & KN_STOLENDROP) ?
+                                THREAD_RESTART : THREAD_AWAKENED;
+
                        kn->kn_status &= ~KN_USEWAIT;
-                       wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_AWAKENED);
+                       waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                          CAST_EVENT64_T(&kn->kn_status),
+                                          result,
+                                          WAITQ_ALL_PRIORITIES);
+               } else {
+                       /* should have seen use-wait if dropping with use refs */
+                       assert((kn->kn_status & (KN_DROPPING|KN_STOLENDROP)) == 0);
+               }
+
+       } else if (kn->kn_status & KN_DROPPING) {
+               /* not the last ref but want to steal a drop if present */
+               if (steal_drop && ((kn->kn_status & KN_STOLENDROP) == 0)) {
+                       kn->kn_status |= KN_STOLENDROP;
+
+                       /* but we now have to wait to be the last ref */
+                       knoteusewait(kq, kn);
+                       kqlock(kq);
+               } else {
+                       dropped = 1;
                }
        }
-       return ((kn->kn_status & KN_DROPPING) == 0);
- }
 
-/* 
- * Convert a kq lock to a knote drop referece.
+       return (!dropped);
+}
+
+/*
+ * Convert a kq lock to a knote use reference
+ * (for the purpose of detaching AND vanishing it).
+ *
+ *     If the knote is being dropped, we can't get
+ *     a detach reference, so wait for the knote to
+ *  finish dropping before returning.
+ *
+ *  If the knote is being used for other purposes,
+ *  we cannot detach it until those uses are done
+ *  as well. Again, just wait for them to finish
+ *  (caller will start over at lookup).
+ *
+ *     - kq locked at entry
+ *     - unlocked on exit
+ */
+static int
+kqlock2knotedetach(struct kqueue *kq, struct knote *kn, int flags)
+{
+       if ((kn->kn_status & KN_DROPPING) || kn->kn_inuse) {
+               /* have to wait for dropper or current uses to go away */
+               knoteusewait(kq, kn);
+               return (0);
+       }
+       assert((kn->kn_status & KN_VANISHED) == 0);
+       assert(kn->kn_status & KN_ATTACHED);
+       kn->kn_status &= ~KN_ATTACHED;
+       kn->kn_status |= KN_VANISHED;
+       if (flags & KNUSE_BOOST) {
+               clear_thread_rwlock_boost();
+       }
+       kn->kn_inuse++;
+       kqunlock(kq);
+       return (1);
+}
+
+/*
+ * Convert a kq lock to a knote drop reference.
  *
  *     If the knote is in use, wait for the use count
  *     to subside.  We first mark our intention to drop
  *     it - keeping other users from "piling on."
  *     If we are too late, we have to wait for the
  *     other drop to complete.
- *     
+ *
  *     - kq locked at entry
  *     - always unlocked on exit.
  *     - caller can't hold any locks that would prevent
@@ -398,62 +796,68 @@ static int
 kqlock2knotedrop(struct kqueue *kq, struct knote *kn)
 {
        int oktodrop;
+       wait_result_t result;
 
        oktodrop = ((kn->kn_status & (KN_DROPPING | KN_ATTACHING)) == 0);
+       /* if another thread is attaching, they will become the dropping thread */
        kn->kn_status |= KN_DROPPING;
+       knote_unsuppress(kn);
+       knote_dequeue(kn);
        if (oktodrop) {
                if (kn->kn_inuse == 0) {
                        kqunlock(kq);
-                       return oktodrop;
+                       return (oktodrop);
                }
        }
-       kn->kn_status |= KN_USEWAIT;
-       wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_UNINT, 0);
-       kqunlock(kq);
-       thread_block(THREAD_CONTINUE_NULL);
-       return oktodrop;
+       result = knoteusewait(kq, kn);
+       /* THREAD_RESTART == another thread stole the knote drop */
+       return (result == THREAD_AWAKENED);
 }
-               
-/* 
+
+#if 0
+/*
  * Release a knote use count reference.
  */
 static void
 knote_put(struct knote *kn)
 {
-       struct kqueue *kq = kn->kn_kq;
+       struct kqueue *kq = knote_get_kq(kn);
 
        kqlock(kq);
        if (--kn->kn_inuse == 0) {
                if ((kn->kn_status & KN_USEWAIT) != 0) {
                        kn->kn_status &= ~KN_USEWAIT;
-                       wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_AWAKENED);
+                       waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                          CAST_EVENT64_T(&kn->kn_status),
+                                          THREAD_AWAKENED,
+                                          WAITQ_ALL_PRIORITIES);
                }
        }
        kqunlock(kq);
- }
+}
+#endif
 
 static int
-filt_fileattach(struct knote *kn)
+filt_fileattach(struct knote *kn, struct kevent_internal_s *kev)
 {
-       
-       return (fo_kqfilter(kn->kn_fp, kn, vfs_context_current()));
+       return (fo_kqfilter(kn->kn_fp, kn, kev, vfs_context_current()));
 }
 
-#define f_flag f_fglob->fg_flag
-#define f_type f_fglob->fg_type
-#define f_msgcount f_fglob->fg_msgcount
-#define f_cred f_fglob->fg_cred
-#define f_ops f_fglob->fg_ops
-#define f_offset f_fglob->fg_offset
-#define f_data f_fglob->fg_data
+#define        f_flag f_fglob->fg_flag
+#define        f_msgcount f_fglob->fg_msgcount
+#define        f_cred f_fglob->fg_cred
+#define        f_ops f_fglob->fg_ops
+#define        f_offset f_fglob->fg_offset
+#define        f_data f_fglob->fg_data
 
 static void
 filt_kqdetach(struct knote *kn)
 {
-       struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;
+       struct kqfile *kqf = (struct kqfile *)kn->kn_fp->f_data;
+       struct kqueue *kq = &kqf->kqf_kqueue;
 
        kqlock(kq);
-       KNOTE_DETACH(&kq->kq_sel.si_note, kn);
+       KNOTE_DETACH(&kqf->kqf_sel.si_note, kn);
        kqunlock(kq);
 }
 
@@ -462,24 +866,70 @@ static int
 filt_kqueue(struct knote *kn, __unused long hint)
 {
        struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;
+       int count;
+
+       count = kq->kq_count;
+       return (count > 0);
+}
+
+static int
+filt_kqtouch(struct knote *kn, struct kevent_internal_s *kev)
+{
+#pragma unused(kev)
+       struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;
+       int res;
+
+       kqlock(kq);
+       kn->kn_data = kq->kq_count;
+       if ((kn->kn_status & KN_UDATA_SPECIFIC) == 0)
+               kn->kn_udata = kev->udata;
+       res = (kn->kn_data > 0);
+
+       kqunlock(kq);
+
+       return res;
+}
+
+static int
+filt_kqprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev)
+{
+#pragma unused(data)
+       struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;
+       int res;
 
+       kqlock(kq);
        kn->kn_data = kq->kq_count;
-       return (kn->kn_data > 0);
+       res = (kn->kn_data > 0);
+       if (res) {
+               *kev = kn->kn_kevent;
+               if (kn->kn_flags & EV_CLEAR)
+                       kn->kn_data = 0;
+       }
+       kqunlock(kq);
+
+       return res;
 }
 
+#pragma mark EVFILT_PROC
+
 static int
-filt_procattach(struct knote *kn)
+filt_procattach(struct knote *kn, __unused struct kevent_internal_s *kev)
 {
        struct proc *p;
 
        assert(PID_MAX < NOTE_PDATAMASK);
-       
-       if ((kn->kn_sfflags & (NOTE_TRACK | NOTE_TRACKERR | NOTE_CHILD)) != 0)
-               return(ENOTSUP);
+
+       if ((kn->kn_sfflags & (NOTE_TRACK | NOTE_TRACKERR | NOTE_CHILD)) != 0) {
+               kn->kn_flags = EV_ERROR;
+               kn->kn_data = ENOTSUP;
+               return 0;
+       }
 
        p = proc_find(kn->kn_id);
        if (p == NULL) {
-               return (ESRCH);
+               kn->kn_flags = EV_ERROR;
+               kn->kn_data = ESRCH;
+               return 0;
        }
 
        const int NoteExitStatusBits = NOTE_EXIT | NOTE_EXITSTATUS;
@@ -496,12 +946,13 @@ filt_procattach(struct knote *kn)
                                break;  /* parent-in-waiting => ok */
 
                        proc_rele(p);
-                       return (EACCES);
+                       kn->kn_flags = EV_ERROR;
+                       kn->kn_data = EACCES;
+                       return 0;
                } while (0);
 
        proc_klist_lock();
 
-       kn->kn_flags |= EV_CLEAR;       /* automatically set */
        kn->kn_ptr.p_proc = p;          /* store the proc handle */
 
        KNOTE_ATTACH(&p->p_klist, kn);
@@ -510,9 +961,14 @@ filt_procattach(struct knote *kn)
 
        proc_rele(p);
 
+       /*
+        * only captures edge-triggered events after this point
+        * so it can't already be fired.
+        */
        return (0);
 }
 
+
 /*
  * The knote may be attached to a different process, which may exit,
  * leaving nothing for the knote to be attached to.  In that case,
@@ -524,7 +980,7 @@ filt_procdetach(struct knote *kn)
        struct proc *p;
 
        proc_klist_lock();
-       
+
        p = kn->kn_ptr.p_proc;
        if (p != PROC_NULL) {
                kn->kn_ptr.p_proc = PROC_NULL;
@@ -537,114 +993,240 @@ filt_procdetach(struct knote *kn)
 static int
 filt_proc(struct knote *kn, long hint)
 {
-       /* hint is 0 when called from above */
-       if (hint != 0) {
-               u_int event;
-
-               /* ALWAYS CALLED WITH proc_klist_lock when (hint != 0) */
+       u_int event;
 
-               /*
-                * mask off extra data
-                */
-               event = (u_int)hint & NOTE_PCTRLMASK;
+       /* ALWAYS CALLED WITH proc_klist_lock */
 
-               /*
-                * if the user is interested in this event, record it.
-                */
-               if (kn->kn_sfflags & event)
-                       kn->kn_fflags |= event;
+       /*
+        * Note: a lot of bits in hint may be obtained from the knote
+        * To free some of those bits, see <rdar://problem/12592988> Freeing up
+        * bits in hint for filt_proc
+        *
+        * mask off extra data
+        */
+       event = (u_int)hint & NOTE_PCTRLMASK;
 
-               if (event == NOTE_REAP || (event == NOTE_EXIT && !(kn->kn_sfflags & NOTE_REAP))) {
-                       kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+       /*
+        * termination lifecycle events can happen while a debugger
+        * has reparented a process, in which case notifications
+        * should be quashed except to the tracing parent. When
+        * the debugger reaps the child (either via wait4(2) or
+        * process exit), the child will be reparented to the original
+        * parent and these knotes re-fired.
+        */
+       if (event & NOTE_EXIT) {
+               if ((kn->kn_ptr.p_proc->p_oppid != 0)
+                   && (knote_get_kq(kn)->kq_p->p_pid != kn->kn_ptr.p_proc->p_ppid)) {
+                       /*
+                        * This knote is not for the current ptrace(2) parent, ignore.
+                        */
+                       return 0;
                }
-               if ((event == NOTE_EXIT) && ((kn->kn_sfflags & NOTE_EXITSTATUS) != 0)) {
+       }                                       
+
+       /*
+        * if the user is interested in this event, record it.
+        */
+       if (kn->kn_sfflags & event)
+               kn->kn_fflags |= event;
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+       if ((event == NOTE_REAP) || ((event == NOTE_EXIT) && !(kn->kn_sfflags & NOTE_REAP))) {
+               kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+       }
+#pragma clang diagnostic pop
+
+
+       /*
+        * The kernel has a wrapper in place that returns the same data
+        * as is collected here, in kn_data.  Any changes to how 
+        * NOTE_EXITSTATUS and NOTE_EXIT_DETAIL are collected
+        * should also be reflected in the proc_pidnoteexit() wrapper.
+        */
+       if (event == NOTE_EXIT) {
+               kn->kn_data = 0;
+               if ((kn->kn_sfflags & NOTE_EXITSTATUS) != 0) {
                        kn->kn_fflags |= NOTE_EXITSTATUS;
-                       kn->kn_data = (hint & NOTE_PDATAMASK);
+                       kn->kn_data |= (hint & NOTE_PDATAMASK);
                }
-               if ((event == NOTE_RESOURCEEND) && ((kn->kn_sfflags & NOTE_RESOURCEEND) != 0)) {
-                       kn->kn_fflags |= NOTE_RESOURCEEND;
-                       kn->kn_data = (hint & NOTE_PDATAMASK);
-               }
-#if CONFIG_EMBEDDED
-               /* If the event is one of the APPSTATE events,remove the rest */
-               if (((event & NOTE_APPALLSTATES) != 0) && ((kn->kn_sfflags & NOTE_APPALLSTATES) != 0)) {
-                       /* only one state at a time */
-                       kn->kn_fflags &= ~NOTE_APPALLSTATES;
-                       kn->kn_fflags |= event;
+               if ((kn->kn_sfflags & NOTE_EXIT_DETAIL) != 0) {
+                       kn->kn_fflags |= NOTE_EXIT_DETAIL;
+                       if ((kn->kn_ptr.p_proc->p_lflag &
+                            P_LTERM_DECRYPTFAIL) != 0) {
+                               kn->kn_data |= NOTE_EXIT_DECRYPTFAIL; 
+                       }
+                       if ((kn->kn_ptr.p_proc->p_lflag &
+                            P_LTERM_JETSAM) != 0) {
+                               kn->kn_data |= NOTE_EXIT_MEMORY;
+                               switch (kn->kn_ptr.p_proc->p_lflag & P_JETSAM_MASK) {
+                               case P_JETSAM_VMPAGESHORTAGE:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_VMPAGESHORTAGE;
+                                       break;
+                               case P_JETSAM_VMTHRASHING:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_VMTHRASHING;
+                                       break;
+                               case P_JETSAM_FCTHRASHING:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_FCTHRASHING;
+                                       break;
+                               case P_JETSAM_VNODE:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_VNODE;
+                                       break;
+                               case P_JETSAM_HIWAT:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_HIWAT;
+                                       break;
+                               case P_JETSAM_PID:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_PID;
+                                       break;
+                               case P_JETSAM_IDLEEXIT:
+                                       kn->kn_data |= NOTE_EXIT_MEMORY_IDLE;
+                                       break;
+                               }
+                       }
+                       if ((kn->kn_ptr.p_proc->p_csflags &
+                            CS_KILLED) != 0) {
+                               kn->kn_data |= NOTE_EXIT_CSERROR;
+                       }
                }
-#endif /* CONFIG_EMBEDDED */
        }
 
-       /* atomic check, no locking need when called from above */
-       return (kn->kn_fflags != 0); 
+       /* if we have any matching state, activate the knote */
+       return (kn->kn_fflags != 0);
 }
 
-#if VM_PRESSURE_EVENTS
-/*
- * Virtual memory kevents
- *
- * author: Matt Jacobson [matthew_jacobson@apple.com]
- */
-
 static int
-filt_vmattach(struct knote *kn)
-{      
-       /* 
-        * The note will be cleared once the information has been flushed to the client. 
-        * If there is still pressure, we will be re-alerted.
-        */
-       kn->kn_flags |= EV_CLEAR; 
-       
-       return vm_knote_register(kn);
-}
+filt_proctouch(struct knote *kn, struct kevent_internal_s *kev)
+{
+       int res;
 
-static void
-filt_vmdetach(struct knote *kn)
-{
-       vm_knote_unregister(kn);
+       proc_klist_lock();
+
+       /* accept new filter flags and mask off output events no long interesting */
+       kn->kn_sfflags = kev->fflags;
+       if ((kn->kn_status & KN_UDATA_SPECIFIC) == 0)
+               kn->kn_udata = kev->udata;
+
+       /* restrict the current results to the (smaller?) set of new interest */
+       /*
+        * For compatibility with previous implementations, we leave kn_fflags
+        * as they were before.
+        */
+       //kn->kn_fflags &= kn->kn_sfflags;
+
+       res = (kn->kn_fflags != 0);
+
+       proc_klist_unlock();
+
+       return res;
 }
 
 static int
-filt_vm(struct knote *kn, long hint)
+filt_procprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev)
 {
-       /* hint == 0 means this is just an alive? check (always true) */
-       if (hint != 0) { 
-               const pid_t pid = (pid_t)hint;
-               if ((kn->kn_sfflags & NOTE_VM_PRESSURE) && (kn->kn_kq->kq_p->p_pid == pid)) {
-                       kn->kn_fflags |= NOTE_VM_PRESSURE;
-               }
+#pragma unused(data)
+       int res;
+
+       proc_klist_lock();
+       res = (kn->kn_fflags != 0);
+       if (res) {
+               *kev = kn->kn_kevent;
+               kn->kn_flags |= EV_CLEAR;       /* automatically set */
+               kn->kn_fflags = 0;
+               kn->kn_data = 0;
        }
-       
-       return (kn->kn_fflags != 0);
+       proc_klist_unlock();
+       return res;
+}
+
+
+#pragma mark EVFILT_TIMER
+
+
+/*
+ * Values stored in the knote at rest (using Mach absolute time units)
+ *
+ * kn->kn_hook          where the thread_call object is stored
+ * kn->kn_ext[0]        next deadline or 0 if immediate expiration
+ * kn->kn_ext[1]        leeway value
+ * kn->kn_sdata         interval timer: the interval
+ *                      absolute/deadline timer: 0
+ * kn->kn_data          fire count
+ */
+
+static lck_mtx_t _filt_timerlock;
+
+static void filt_timerlock(void)   { lck_mtx_lock(&_filt_timerlock);   }
+static void filt_timerunlock(void) { lck_mtx_unlock(&_filt_timerlock); }
+
+static inline void filt_timer_assert_locked(void)
+{
+       LCK_MTX_ASSERT(&_filt_timerlock, LCK_MTX_ASSERT_OWNED);
 }
-#endif /* VM_PRESSURE_EVENTS */
+
+/* state flags stored in kn_hookid */
+#define        TIMER_RUNNING           0x1
+#define        TIMER_CANCELWAIT        0x2
 
 /*
  * filt_timervalidate - process data from user
- *     
- *     Converts to either interval or deadline format.
- *     
- *     The saved-data field in the knote contains the
- *     time value.  The saved filter-flags indicates
- *     the unit of measurement.
  *
- *     After validation, either the saved-data field 
- *     contains the interval in absolute time, or ext[0] 
- *     contains the expected deadline. If that deadline 
- *     is in the past, ext[0] is 0.
+ * Sets up the deadline, interval, and leeway from the provided user data
+ *
+ * Input:
+ *      kn_sdata        timer deadline or interval time
+ *      kn_sfflags      style of timer, unit of measurement
  *
- *     Returns EINVAL for unrecognized units of time.
+ * Output:
+ *      kn_sdata        either interval in abstime or 0 if non-repeating timer
+ *      ext[0]          fire deadline in abs/cont time
+ *                      (or 0 if NOTE_ABSOLUTE and deadline is in past)
  *
- *     Timer filter lock is held.
+ * Returns:
+ *      EINVAL          Invalid user data parameters
  *
+ * Called with timer filter lock held.
  */
 static int
 filt_timervalidate(struct knote *kn)
 {
+       /*
+        * There are 4 knobs that need to be chosen for a timer registration:
+        *
+        * A) Units of time (what is the time duration of the specified number)
+        *      Absolute and interval take:
+        *              NOTE_SECONDS, NOTE_USECONDS, NOTE_NSECONDS, NOTE_MACHTIME
+        *      Defaults to milliseconds if not specified
+        *
+        * B) Clock epoch (what is the zero point of the specified number)
+        *      For interval, there is none
+        *      For absolute, defaults to the gettimeofday/calendar epoch
+        *      With NOTE_MACHTIME, uses mach_absolute_time()
+        *      With NOTE_MACHTIME and NOTE_MACH_CONTINUOUS_TIME, uses mach_continuous_time()
+        *
+        * C) The knote's behavior on delivery
+        *      Interval timer causes the knote to arm for the next interval unless one-shot is set
+        *      Absolute is a forced one-shot timer which deletes on delivery
+        *      TODO: Add a way for absolute to be not forced one-shot
+        *
+        * D) Whether the time duration is relative to now or absolute
+        *      Interval fires at now + duration when it is set up
+        *      Absolute fires at now + difference between now walltime and passed in walltime
+        *      With NOTE_MACHTIME it fires at an absolute MAT or MCT.
+        *
+        * E) Whether the timer continues to tick across sleep
+        *      By default all three do not.
+        *      For interval and absolute, NOTE_MACH_CONTINUOUS_TIME causes them to tick across sleep
+        *      With NOTE_ABSOLUTE | NOTE_MACHTIME | NOTE_MACH_CONTINUOUS_TIME:
+        *              expires when mach_continuous_time() is > the passed in value.
+        */
+
+       filt_timer_assert_locked();
+
        uint64_t multiplier;
-       uint64_t raw;
 
-       switch (kn->kn_sfflags & (NOTE_SECONDS|NOTE_USECONDS|NOTE_NSECONDS)) {
+       boolean_t use_abstime = FALSE;
+
+       switch (kn->kn_sfflags & (NOTE_SECONDS|NOTE_USECONDS|NOTE_NSECONDS|NOTE_MACHTIME)) {
        case NOTE_SECONDS:
                multiplier = NSEC_PER_SEC;
                break;
@@ -654,84 +1236,143 @@ filt_timervalidate(struct knote *kn)
        case NOTE_NSECONDS:
                multiplier = 1;
                break;
+       case NOTE_MACHTIME:
+               multiplier = 0;
+               use_abstime = TRUE;
+               break;
        case 0: /* milliseconds (default) */
                multiplier = NSEC_PER_SEC / 1000;
                break;
        default:
-               return EINVAL;
+               return (EINVAL);
        }
 
-       nanoseconds_to_absolutetime((uint64_t)kn->kn_sdata * multiplier, &raw);
+       /* transform the leeway in kn_ext[1] to same time scale */
+       if (kn->kn_sfflags & NOTE_LEEWAY) {
+               uint64_t leeway_abs;
 
-       kn->kn_ext[0] = 0;
-       kn->kn_sdata = 0;
+               if (use_abstime) {
+                       leeway_abs = (uint64_t)kn->kn_ext[1];
+               } else  {
+                       uint64_t leeway_ns;
+                       if (os_mul_overflow((uint64_t)kn->kn_ext[1], multiplier, &leeway_ns))
+                               return (ERANGE);
 
-       if (kn->kn_sfflags & NOTE_ABSOLUTE) {
-               clock_sec_t seconds;
-               clock_nsec_t nanoseconds;
-               uint64_t now;
+                       nanoseconds_to_absolutetime(leeway_ns, &leeway_abs);
+               }
+
+               kn->kn_ext[1] = leeway_abs;
+       }
 
-               clock_get_calendar_nanotime(&seconds, &nanoseconds);
-               nanoseconds_to_absolutetime((uint64_t)seconds * NSEC_PER_SEC + 
-                               nanoseconds, &now);
+       if (kn->kn_sfflags & NOTE_ABSOLUTE) {
+               uint64_t deadline_abs;
 
-               if (raw < now) {
-                       /* time has already passed */
-                       kn->kn_ext[0] = 0;
+               if (use_abstime) {
+                       deadline_abs = (uint64_t)kn->kn_sdata;
                } else {
-                       raw -= now;
-                       clock_absolutetime_interval_to_deadline(raw, 
-                                       &kn->kn_ext[0]);
-               }
-       } else {
-               kn->kn_sdata = raw;
-       }
+                       uint64_t calendar_deadline_ns;
 
-       return 0;
-}
+                       if (os_mul_overflow((uint64_t)kn->kn_sdata, multiplier, &calendar_deadline_ns))
+                               return (ERANGE);
 
-/*
- * filt_timerupdate - compute the next deadline
- *
- *     Repeating timers store their interval in kn_sdata. Absolute
- *     timers have already calculated the deadline, stored in ext[0].
- *
- *     On return, the next deadline (or zero if no deadline is needed)
- *     is stored in kn_ext[0].
- *
- *     Timer filter lock is held.
- */
-static void 
-filt_timerupdate(struct knote *kn)
-{
-       /* if there's no interval, deadline is just in kn_ext[0] */
-       if (kn->kn_sdata == 0)
-               return;
+                       /* calendar_deadline_ns is in nanoseconds since the epoch */
 
-       /* if timer hasn't fired before, fire in interval nsecs */
-       if (kn->kn_ext[0] == 0) {
-               clock_absolutetime_interval_to_deadline(kn->kn_sdata,
-                               &kn->kn_ext[0]);
-       } else {
-               /* 
-                * If timer has fired before, schedule the next pop 
-                * relative to the last intended deadline. 
+                       clock_sec_t seconds;
+                       clock_nsec_t nanoseconds;
+
+                       /*
+                        * Note that the conversion through wall-time is only done once.
+                        *
+                        * If the relationship between MAT and gettimeofday changes,
+                        * the underlying timer does not update.
+                        *
+                        * TODO: build a wall-time denominated timer_call queue
+                        * and a flag to request DTRTing with wall-time timers
+                        */
+                       clock_get_calendar_nanotime(&seconds, &nanoseconds);
+
+                       uint64_t calendar_now_ns = (uint64_t)seconds * NSEC_PER_SEC + nanoseconds;
+
+                       /* if deadline is in the future */
+                       if (calendar_now_ns < calendar_deadline_ns) {
+                               uint64_t interval_ns = calendar_deadline_ns - calendar_now_ns;
+                               uint64_t interval_abs;
+
+                               nanoseconds_to_absolutetime(interval_ns, &interval_abs);
+
+                               /*
+                                * Note that the NOTE_MACH_CONTINUOUS_TIME flag here only
+                                * causes the timer to keep ticking across sleep, but
+                                * it does not change the calendar timebase.
+                                */
+
+                               if (kn->kn_sfflags & NOTE_MACH_CONTINUOUS_TIME)
+                                       clock_continuoustime_interval_to_deadline(interval_abs,
+                                                                                 &deadline_abs);
+                               else
+                                       clock_absolutetime_interval_to_deadline(interval_abs,
+                                                                               &deadline_abs);
+                       } else {
+                               deadline_abs = 0; /* cause immediate expiration */
+                       }
+               }
+
+               kn->kn_ext[0] = deadline_abs;
+               kn->kn_sdata  = 0;       /* NOTE_ABSOLUTE is non-repeating */
+       } else if (kn->kn_sdata < 0) {
+               /*
+                * Negative interval timers fire immediately, once.
+                *
+                * Ideally a negative interval would be an error, but certain clients
+                * pass negative values on accident, and expect an event back.
                 *
-                * We could check for whether the deadline has expired, 
-                * but the thread call layer can handle that.
+                * In the old implementation the timer would repeat with no delay
+                * N times until mach_absolute_time() + (N * interval) underflowed,
+                * then it would wait ~forever by accidentally arming a timer for the far future.
+                *
+                * We now skip the power-wasting hot spin phase and go straight to the idle phase.
                 */
-               kn->kn_ext[0] += kn->kn_sdata;
+
+               kn->kn_sdata  = 0;      /* non-repeating */
+               kn->kn_ext[0] = 0;      /* expire immediately */
+       } else {
+               uint64_t interval_abs = 0;
+
+               if (use_abstime) {
+                       interval_abs = (uint64_t)kn->kn_sdata;
+               } else {
+                       uint64_t interval_ns;
+                       if (os_mul_overflow((uint64_t)kn->kn_sdata, multiplier, &interval_ns))
+                               return (ERANGE);
+
+                       nanoseconds_to_absolutetime(interval_ns, &interval_abs);
+               }
+
+               uint64_t deadline = 0;
+
+               if (kn->kn_sfflags & NOTE_MACH_CONTINUOUS_TIME)
+                       clock_continuoustime_interval_to_deadline(interval_abs, &deadline);
+               else
+                       clock_absolutetime_interval_to_deadline(interval_abs, &deadline);
+
+               kn->kn_sdata  = interval_abs;   /* default to a repeating timer */
+               kn->kn_ext[0] = deadline;
        }
+
+       return (0);
 }
 
-/* 
+
+
+
+/*
  * filt_timerexpire - the timer callout routine
  *
- *     Just propagate the timer event into the knote
- *     filter routine (by going through the knote
- *     synchronization point).  Pass a hint to
- *     indicate this is a real event, not just a
- *     query from above.
+ * Just propagate the timer event into the knote
+ * filter routine (by going through the knote
+ * synchronization point).  Pass a hint to
+ * indicate this is a real event, not just a
+ * query from above.
  */
 static void
 filt_timerexpire(void *knx, __unused void *spare)
@@ -745,14 +1386,19 @@ filt_timerexpire(void *knx, __unused void *spare)
 
        /* no "object" for timers, so fake a list */
        SLIST_INIT(&timer_list);
-       SLIST_INSERT_HEAD(&timer_list, kn, kn_selnext); 
+       SLIST_INSERT_HEAD(&timer_list, kn, kn_selnext);
+
        KNOTE(&timer_list, 1);
 
        /* if someone is waiting for timer to pop */
        if (kn->kn_hookid & TIMER_CANCELWAIT) {
-               struct kqueue *kq = kn->kn_kq;
-               wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_hook, 
-                               THREAD_AWAKENED);
+               struct kqueue *kq = knote_get_kq(kn);
+               waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                  CAST_EVENT64_T(&kn->kn_hook),
+                                  THREAD_AWAKENED,
+                                  WAITQ_ALL_PRIORITIES);
+
+               kn->kn_hookid &= ~TIMER_CANCELWAIT;
        }
 
        filt_timerunlock();
@@ -761,71 +1407,152 @@ filt_timerexpire(void *knx, __unused void *spare)
 /*
  * Cancel a running timer (or wait for the pop).
  * Timer filter lock is held.
+ * May drop and retake the timer filter lock.
  */
 static void
 filt_timercancel(struct knote *kn)
 {
-       struct kqueue *kq = kn->kn_kq;
-       thread_call_t callout = kn->kn_hook;
-       boolean_t cancelled;
+       filt_timer_assert_locked();
 
-       if (kn->kn_hookid & TIMER_RUNNING) {
-               /* cancel the callout if we can */
-               cancelled = thread_call_cancel(callout);
-               if (cancelled) {
-                       kn->kn_hookid &= ~TIMER_RUNNING;
-               } else {
-                       /* we have to wait for the expire routine.  */
-                       kn->kn_hookid |= TIMER_CANCELWAIT;
-                       wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, 
-                                       &kn->kn_hook, THREAD_UNINT, 0);
-                       filt_timerunlock();
-                       thread_block(THREAD_CONTINUE_NULL);
-                       filt_timerlock();
-                       assert((kn->kn_hookid & TIMER_RUNNING) == 0);
-               }
+       assert((kn->kn_hookid & TIMER_CANCELWAIT) == 0);
+
+       /* if no timer, then we're good */
+       if ((kn->kn_hookid & TIMER_RUNNING) == 0)
+               return;
+
+       thread_call_t callout = (thread_call_t)kn->kn_hook;
+
+       /* cancel the callout if we can */
+       if (thread_call_cancel(callout)) {
+               kn->kn_hookid &= ~TIMER_RUNNING;
+               return;
        }
+
+       /* cancel failed, we have to wait for the in-flight expire routine */
+
+       kn->kn_hookid |= TIMER_CANCELWAIT;
+
+       struct kqueue *kq = knote_get_kq(kn);
+
+       waitq_assert_wait64((struct waitq *)&kq->kq_wqs,
+                           CAST_EVENT64_T(&kn->kn_hook),
+                           THREAD_UNINT, TIMEOUT_WAIT_FOREVER);
+
+       filt_timerunlock();
+       thread_block(THREAD_CONTINUE_NULL);
+       filt_timerlock();
+
+       assert((kn->kn_hookid & TIMER_CANCELWAIT) == 0);
+       assert((kn->kn_hookid & TIMER_RUNNING) == 0);
+}
+
+static void
+filt_timerarm(struct knote *kn)
+{
+       filt_timer_assert_locked();
+
+       assert((kn->kn_hookid & TIMER_RUNNING) == 0);
+
+       thread_call_t callout = (thread_call_t)kn->kn_hook;
+
+       uint64_t deadline = kn->kn_ext[0];
+       uint64_t leeway   = kn->kn_ext[1];
+
+       int filter_flags = kn->kn_sfflags;
+       unsigned int timer_flags = 0;
+
+       if (filter_flags & NOTE_CRITICAL)
+               timer_flags |= THREAD_CALL_DELAY_USER_CRITICAL;
+       else if (filter_flags & NOTE_BACKGROUND)
+               timer_flags |= THREAD_CALL_DELAY_USER_BACKGROUND;
+       else
+               timer_flags |= THREAD_CALL_DELAY_USER_NORMAL;
+
+       if (filter_flags & NOTE_LEEWAY)
+               timer_flags |= THREAD_CALL_DELAY_LEEWAY;
+
+       if (filter_flags & NOTE_MACH_CONTINUOUS_TIME)
+               timer_flags |= THREAD_CALL_CONTINUOUS;
+
+       thread_call_enter_delayed_with_leeway(callout, NULL,
+                                             deadline, leeway,
+                                             timer_flags);
+
+       kn->kn_hookid |= TIMER_RUNNING;
+}
+
+/*
+ * Does this knote need a timer armed for it, or should it be ready immediately?
+ */
+static boolean_t
+filt_timer_is_ready(struct knote *kn)
+{
+       uint64_t now;
+
+       if (kn->kn_sfflags & NOTE_MACH_CONTINUOUS_TIME)
+               now = mach_continuous_time();
+       else
+               now = mach_absolute_time();
+
+       uint64_t deadline = kn->kn_ext[0];
+
+       if (deadline < now)
+               return TRUE;
+       else
+               return FALSE;
 }
 
 /*
  * Allocate a thread call for the knote's lifetime, and kick off the timer.
- */ 
+ */
 static int
-filt_timerattach(struct knote *kn)
+filt_timerattach(struct knote *kn, __unused struct kevent_internal_s *kev)
 {
        thread_call_t callout;
        int error;
 
-       callout = thread_call_allocate(filt_timerexpire, kn);
-       if (NULL == callout)
-               return (ENOMEM);
+       callout = thread_call_allocate_with_options(filt_timerexpire,
+                       (thread_call_param_t)kn, THREAD_CALL_PRIORITY_HIGH,
+                       THREAD_CALL_OPTIONS_ONCE);
+
+       if (NULL == callout) {
+               kn->kn_flags = EV_ERROR;
+               kn->kn_data = ENOMEM;
+               return 0;
+       }
 
        filt_timerlock();
-       error = filt_timervalidate(kn);
-       if (error) {
+
+       if ((error = filt_timervalidate(kn)) != 0) {
+               kn->kn_flags = EV_ERROR;
+               kn->kn_data  = error;
                filt_timerunlock();
-               return (error);
+
+               __assert_only boolean_t freed = thread_call_free(callout);
+               assert(freed);
+               return 0;
        }
 
        kn->kn_hook = (void*)callout;
        kn->kn_hookid = 0;
+       kn->kn_flags |= EV_CLEAR;
 
-       /* absolute=EV_ONESHOT */
+       /* NOTE_ABSOLUTE implies EV_ONESHOT */
        if (kn->kn_sfflags & NOTE_ABSOLUTE)
-               kn->kn_flags |= EV_ONESHOT; 
+               kn->kn_flags |= EV_ONESHOT;
 
-       filt_timerupdate(kn);
-       if (kn->kn_ext[0]) {
-               kn->kn_flags |= EV_CLEAR;
-               thread_call_enter_delayed(callout, kn->kn_ext[0]);
-               kn->kn_hookid |= TIMER_RUNNING;
-       } else {
-               /* fake immediate */
+       boolean_t timer_ready = FALSE;
+
+       if ((timer_ready = filt_timer_is_ready(kn))) {
+               /* cause immediate expiration */
                kn->kn_data = 1;
+       } else {
+               filt_timerarm(kn);
        }
 
        filt_timerunlock();
-       return (0);
+
+       return timer_ready;
 }
 
 /*
@@ -840,2159 +1567,8173 @@ filt_timerdetach(struct knote *kn)
 
        callout = (thread_call_t)kn->kn_hook;
        filt_timercancel(kn);
-       
-       filt_timerunlock(); 
 
-       thread_call_free(callout);
+       filt_timerunlock();
+
+       __assert_only boolean_t freed = thread_call_free(callout);
+       assert(freed);
 }
 
+/*
+ * filt_timerevent - post events to a timer knote
+ *
+ * Called in the context of filt_timerexpire with
+ * the filt_timerlock held
+ */
+static int
+filt_timerevent(struct knote *kn, __unused long hint)
+{
+       filt_timer_assert_locked();
 
+       kn->kn_data = 1;
+       return (1);
+}
 
+/*
+ * filt_timertouch - update timer knote with new user input
+ *
+ * Cancel and restart the timer based on new user data. When
+ * the user picks up a knote, clear the count of how many timer
+ * pops have gone off (in kn_data).
+ */
 static int
-filt_timer(struct knote *kn, long hint)
+filt_timertouch(
+       struct knote *kn,
+       struct kevent_internal_s *kev)
 {
-       int result;
-       
-       if (hint) {
-               /* real timer pop -- timer lock held by filt_timerexpire */
+       int error;
 
-               kn->kn_data++;
+       filt_timerlock();
+
+       /*
+        * cancel current call - drops and retakes lock
+        * TODO: not safe against concurrent touches?
+        */
+       filt_timercancel(kn);
 
-               if (((kn->kn_hookid & TIMER_CANCELWAIT) == 0) && 
-                               ((kn->kn_flags & EV_ONESHOT) == 0)) {
+       /* clear if the timer had previously fired, the user no longer wants to see it */
+       kn->kn_data = 0;
 
-                       /* evaluate next time to fire */
-                       filt_timerupdate(kn);
+       /* capture the new values used to compute deadline */
+       kn->kn_sdata = kev->data;
+       kn->kn_sfflags = kev->fflags;
+       kn->kn_ext[0] = kev->ext[0];
+       kn->kn_ext[1] = kev->ext[1];
 
-                       if (kn->kn_ext[0]) {
-                               /* keep the callout and re-arm */
-                               thread_call_enter_delayed(kn->kn_hook, 
-                                               kn->kn_ext[0]);
-                               kn->kn_hookid |= TIMER_RUNNING;
-                       }
-               }
+       if ((kn->kn_status & KN_UDATA_SPECIFIC) == 0)
+               kn->kn_udata = kev->udata;
 
+       /* recalculate deadline */
+       error = filt_timervalidate(kn);
+       if (error) {
+               /* no way to report error, so mark it in the knote */
+               kn->kn_flags |= EV_ERROR;
+               kn->kn_data = error;
+               filt_timerunlock();
                return 1;
-       } 
+       }
 
-       /* user-query */
-       filt_timerlock();
+       boolean_t timer_ready = FALSE;
 
-       result = (kn->kn_data != 0);
+       if ((timer_ready = filt_timer_is_ready(kn))) {
+               /* cause immediate expiration */
+               kn->kn_data = 1;
+       } else {
+               filt_timerarm(kn);
+       }
 
        filt_timerunlock();
-       return result;
-}
 
+       return timer_ready;
+}
 
 /*
- * filt_timertouch - update knote with new user input
+ * filt_timerprocess - query state of knote and snapshot event data
  *
- *     Cancel and restart the timer based on new user data. When
- *     the user picks up a knote, clear the count of how many timer
- *     pops have gone off (in kn_data).
+ * Determine if the timer has fired in the past, snapshot the state
+ * of the kevent for returning to user-space, and clear pending event
+ * counters for the next time.
  */
-static void     
-filt_timertouch(struct knote *kn, struct kevent64_s *kev, long type)
+static int
+filt_timerprocess(
+       struct knote *kn,
+       __unused struct filt_process_s *data,
+       struct kevent_internal_s *kev)
 {
-       int error;
        filt_timerlock();
 
-       switch (type) {
-       case EVENT_REGISTER:
-               /* cancel current call */
-               filt_timercancel(kn);
+       if (kn->kn_data == 0 || (kn->kn_hookid & TIMER_CANCELWAIT)) {
+               /*
+                * kn_data = 0:
+                * The timer hasn't yet fired, so there's nothing to deliver
+                * TIMER_CANCELWAIT:
+                * touch is in the middle of canceling the timer,
+                * so don't deliver or re-arm anything
+                *
+                * This can happen if a touch resets a timer that had fired
+                * without being processed
+                */
+               filt_timerunlock();
+               return 0;
+       }
 
-               /* recalculate deadline */
-               kn->kn_sdata = kev->data;
-               kn->kn_sfflags = kev->fflags;
+       if (kn->kn_sdata != 0 && ((kn->kn_flags & EV_ERROR) == 0)) {
+               /*
+                * This is a 'repeating' timer, so we have to emit
+                * how many intervals expired between the arm
+                * and the process.
+                *
+                * A very strange style of interface, because
+                * this could easily be done in the client...
+                */
 
-               error = filt_timervalidate(kn);
-               if (error) {
-                       /* no way to report error, so mark it in the knote */
-                       kn->kn_flags |= EV_ERROR;
-                       kn->kn_data = error;
-                       break;
-               } 
+               /* The timer better have had expired... */
+               assert((kn->kn_hookid & TIMER_RUNNING) == 0);
 
-               /* start timer if necessary */
-               filt_timerupdate(kn);
-               if (kn->kn_ext[0]) {
-                       thread_call_enter_delayed(kn->kn_hook, kn->kn_ext[0]);
-                       kn->kn_hookid |= TIMER_RUNNING;
-               } else {
-                       /* pretend the timer has fired */
-                       kn->kn_data = 1;
-               }
+               uint64_t now;
 
-               break;
+               if (kn->kn_sfflags & NOTE_MACH_CONTINUOUS_TIME)
+                       now = mach_continuous_time();
+               else
+                       now = mach_absolute_time();
 
-       case EVENT_PROCESS:
-               /* reset the timer pop count in kn_data */
-               *kev = kn->kn_kevent;
-               kev->ext[0] = 0;
-               kn->kn_data = 0;
-               if (kn->kn_flags & EV_CLEAR)
-                       kn->kn_fflags = 0;
-               break;
-       default:
-               panic("filt_timertouch() - invalid type (%ld)", type);
-               break;
+               uint64_t first_deadline = kn->kn_ext[0];
+               uint64_t interval_abs   = kn->kn_sdata;
+               uint64_t orig_arm_time  = first_deadline - interval_abs;
+
+               assert(now > orig_arm_time);
+               assert(now > first_deadline);
+
+               uint64_t elapsed = now - orig_arm_time;
+
+               uint64_t num_fired = elapsed / interval_abs;
+
+               /*
+                * To reach this code, we must have seen the timer pop
+                * and be in repeating mode, so therefore it must have been
+                * more than 'interval' time since the attach or last
+                * successful touch.
+                *
+                * An unsuccessful touch would:
+                * disarm the timer
+                * clear kn_data
+                * clear kn_sdata
+                * set EV_ERROR
+                * all of which will prevent this code from running.
+                */
+               assert(num_fired > 0);
+
+               /* report how many intervals have elapsed to the user */
+               kn->kn_data = (int64_t) num_fired;
+
+               /* We only need to re-arm the timer if it's not about to be destroyed */
+               if ((kn->kn_flags & EV_ONESHOT) == 0) {
+                       /* fire at the end of the next interval */
+                       uint64_t new_deadline = first_deadline + num_fired * interval_abs;
+
+                       assert(new_deadline > now);
+
+                       kn->kn_ext[0] = new_deadline;
+
+                       filt_timerarm(kn);
+               }
        }
 
+       /*
+        * Copy out the interesting kevent state,
+        * but don't leak out the raw time calculations.
+        *
+        * TODO: potential enhancements - tell the user about:
+        *      - deadline to which this timer thought it was expiring
+        *      - return kn_sfflags in the fflags field so the client can know
+        *        under what flags the timer fired
+        */
+       *kev = kn->kn_kevent;
+       kev->ext[0] = 0;
+       /* kev->ext[1] = 0;  JMM - shouldn't we hide this too? */
+
+       /* we have delivered the event, reset the timer pop count */
+       kn->kn_data = 0;
+
        filt_timerunlock();
+       return 1;
 }
 
+SECURITY_READ_ONLY_EARLY(static struct filterops) timer_filtops = {
+       .f_attach   = filt_timerattach,
+       .f_detach   = filt_timerdetach,
+       .f_event    = filt_timerevent,
+       .f_touch    = filt_timertouch,
+       .f_process  = filt_timerprocess,
+};
+
+
+#pragma mark EVFILT_USER
+
+
 static void
-filt_timerlock(void)
+filt_userlock(void)
 {
-       lck_mtx_lock(&_filt_timerlock);
+       lck_spin_lock(&_filt_userlock);
 }
 
 static void
-filt_timerunlock(void)
+filt_userunlock(void)
 {
-       lck_mtx_unlock(&_filt_timerlock);
+       lck_spin_unlock(&_filt_userlock);
 }
 
 static int
-filt_userattach(struct knote *kn)
+filt_userattach(struct knote *kn, __unused struct kevent_internal_s *kev)
 {
-        /* EVFILT_USER knotes are not attached to anything in the kernel */
-        kn->kn_hook = NULL;
-       if (kn->kn_fflags & NOTE_TRIGGER) {
+       /* EVFILT_USER knotes are not attached to anything in the kernel */
+       /* Cant discover this knote until after attach - so no lock needed */
+       kn->kn_hook = NULL;
+       if (kn->kn_sfflags & NOTE_TRIGGER) {
                kn->kn_hookid = 1;
        } else {
                kn->kn_hookid = 0;
        }
-        return 0;
+       return (kn->kn_hookid);
 }
 
 static void
 filt_userdetach(__unused struct knote *kn)
 {
-        /* EVFILT_USER knotes are not attached to anything in the kernel */
+       /* EVFILT_USER knotes are not attached to anything in the kernel */
 }
 
 static int
-filt_user(struct knote *kn, __unused long hint)
+filt_user(
+       __unused struct knote *kn,
+       __unused long hint)
 {
-        return kn->kn_hookid;
-}
-
-static void
-filt_usertouch(struct knote *kn, struct kevent64_s *kev, long type)
-{
-        uint32_t ffctrl;
-        switch (type) {
-        case EVENT_REGISTER:
-                if (kev->fflags & NOTE_TRIGGER) {
-                        kn->kn_hookid = 1;
-                }
-
-                ffctrl = kev->fflags & NOTE_FFCTRLMASK;
-                kev->fflags &= NOTE_FFLAGSMASK;
-                switch (ffctrl) {
-                case NOTE_FFNOP:
-                        break;
-                case NOTE_FFAND:
-                        OSBitAndAtomic(kev->fflags, &kn->kn_sfflags);
-                        break;
-                case NOTE_FFOR:
-                        OSBitOrAtomic(kev->fflags, &kn->kn_sfflags);
-                        break;
-                case NOTE_FFCOPY:
-                        kn->kn_sfflags = kev->fflags;
-                        break;
-                }
-                kn->kn_sdata = kev->data;
-                break;
-        case EVENT_PROCESS:
-                *kev = kn->kn_kevent;
-                kev->fflags = (volatile UInt32)kn->kn_sfflags;
-                kev->data = kn->kn_sdata;
-                if (kn->kn_flags & EV_CLEAR) {
-                       kn->kn_hookid = 0;
-                       kn->kn_data = 0;
-                       kn->kn_fflags = 0;
-               }
-                break;
-        default:
-                panic("filt_usertouch() - invalid type (%ld)", type);
-                break;
-        }
+       panic("filt_user");
+       return 0;
 }
 
-/*
- * JMM - placeholder for not-yet-implemented filters
- */ 
 static int
-filt_badattach(__unused struct knote *kn)
+filt_usertouch(
+       struct knote *kn,
+       struct kevent_internal_s *kev)
 {
-       return(ENOTSUP);
-}
-
+       uint32_t ffctrl;
+       int fflags;
+       int active;
 
-struct kqueue *
-kqueue_alloc(struct proc *p)
-{
-       struct filedesc *fdp = p->p_fd;
-       struct kqueue *kq;
+       filt_userlock();
 
-       MALLOC_ZONE(kq, struct kqueue *, sizeof(struct kqueue), M_KQUEUE, M_WAITOK);
-       if (kq != NULL) {
-               wait_queue_set_t wqs;
-
-               wqs = wait_queue_set_alloc(SYNC_POLICY_FIFO | SYNC_POLICY_PREPOST);
-               if (wqs != NULL) {
-                       bzero(kq, sizeof(struct kqueue));
-                       lck_spin_init(&kq->kq_lock, kq_lck_grp, kq_lck_attr);
-                       TAILQ_INIT(&kq->kq_head);
-                       kq->kq_wqs = wqs;
-                       kq->kq_p = p;
-               } else {
-                       FREE_ZONE(kq, sizeof(struct kqueue), M_KQUEUE);
-               }
+       ffctrl = kev->fflags & NOTE_FFCTRLMASK;
+       fflags = kev->fflags & NOTE_FFLAGSMASK;
+       switch (ffctrl) {
+       case NOTE_FFNOP:
+               break;
+       case NOTE_FFAND:
+               kn->kn_sfflags &= fflags;
+               break;
+       case NOTE_FFOR:
+               kn->kn_sfflags |= fflags;
+               break;
+       case NOTE_FFCOPY:
+               kn->kn_sfflags = fflags;
+               break;
        }
+       kn->kn_sdata = kev->data;
 
-       if (fdp->fd_knlistsize < 0) {
-               proc_fdlock(p);
-               if (fdp->fd_knlistsize < 0)
-                       fdp->fd_knlistsize = 0;         /* this process has had a kq */
-               proc_fdunlock(p);
+       if ((kn->kn_status & KN_UDATA_SPECIFIC) == 0)
+               kn->kn_udata = kev->udata;
+
+       if (kev->fflags & NOTE_TRIGGER) {
+               kn->kn_hookid = 1;
        }
+       active = kn->kn_hookid;
 
-       return kq;
-}
+       filt_userunlock();
 
+       return (active);
+}
 
-/*
- * kqueue_dealloc - detach all knotes from a kqueue and free it
- *
- *     We walk each list looking for knotes referencing this
- *     this kqueue.  If we find one, we try to drop it.  But
- *     if we fail to get a drop reference, that will wait
- *     until it is dropped.  So, we can just restart again
- *     safe in the assumption that the list will eventually
- *     not contain any more references to this kqueue (either
- *     we dropped them all, or someone else did).
- *
- *     Assumes no new events are being added to the kqueue.
- *     Nothing locked on entry or exit.
- */
-void
-kqueue_dealloc(struct kqueue *kq)
+static int
+filt_userprocess(
+       struct knote *kn,
+       __unused struct filt_process_s *data,
+       struct kevent_internal_s *kev)
 {
-       struct proc *p = kq->kq_p;
-       struct filedesc *fdp = p->p_fd;
-       struct knote *kn;
-       int i;
+       filt_userlock();
 
-       proc_fdlock(p);
-       for (i = 0; i < fdp->fd_knlistsize; i++) {
-               kn = SLIST_FIRST(&fdp->fd_knlist[i]);
-               while (kn != NULL) {
-                       if (kq == kn->kn_kq) {
-                               kqlock(kq);
-                               proc_fdunlock(p);
-                               /* drop it ourselves or wait */
-                               if (kqlock2knotedrop(kq, kn)) {
-                                       kn->kn_fop->f_detach(kn);
-                                       knote_drop(kn, p);
-                               }
-                               proc_fdlock(p);
-                               /* start over at beginning of list */
-                               kn = SLIST_FIRST(&fdp->fd_knlist[i]);
-                               continue;
-                       }
-                       kn = SLIST_NEXT(kn, kn_link);
-               }
+       if (kn->kn_hookid == 0) {
+               filt_userunlock();
+               return 0;
        }
-       if (fdp->fd_knhashmask != 0) {
-               for (i = 0; i < (int)fdp->fd_knhashmask + 1; i++) {
-                       kn = SLIST_FIRST(&fdp->fd_knhash[i]);
-                       while (kn != NULL) {
-                               if (kq == kn->kn_kq) {
-                                       kqlock(kq);
-                                       proc_fdunlock(p);
-                                       /* drop it ourselves or wait */
-                                       if (kqlock2knotedrop(kq, kn)) {
-                                               kn->kn_fop->f_detach(kn);
-                                               knote_drop(kn, p);
-                                       }
-                                       proc_fdlock(p);
-                                       /* start over at beginning of list */
-                                       kn = SLIST_FIRST(&fdp->fd_knhash[i]);
-                                       continue;
-                               }
-                               kn = SLIST_NEXT(kn, kn_link);
-                       }
-               }
+
+       *kev = kn->kn_kevent;
+       kev->fflags = (volatile UInt32)kn->kn_sfflags;
+       kev->data = kn->kn_sdata;
+       if (kn->kn_flags & EV_CLEAR) {
+               kn->kn_hookid = 0;
+               kn->kn_data = 0;
+               kn->kn_fflags = 0;
        }
-       proc_fdunlock(p);
+       filt_userunlock();
 
-       /* 
-        * before freeing the wait queue set for this kqueue,
-        * make sure it is unlinked from all its containing (select) sets.
-        */
-       wait_queue_unlink_all((wait_queue_t)kq->kq_wqs);
-       wait_queue_set_free(kq->kq_wqs);
-       lck_spin_destroy(&kq->kq_lock, kq_lck_grp);
-       FREE_ZONE(kq, sizeof(struct kqueue), M_KQUEUE);
+       return 1;
 }
 
-int
-kqueue(struct proc *p, __unused struct kqueue_args *uap, int32_t *retval)
-{
-       struct kqueue *kq;
-       struct fileproc *fp;
-       int fd, error;
-
-       error = falloc(p, &fp, &fd, vfs_context_current());
-       if (error) {
-               return (error);
-       }
+#pragma mark EVFILT_WORKLOOP
 
-       kq = kqueue_alloc(p);
-       if (kq == NULL) {
-               fp_free(p, fd, fp);
-               return (ENOMEM);
-       }
+#if DEBUG || DEVELOPMENT
+/*
+ * see src/queue_internal.h in libdispatch
+ */
+#define DISPATCH_QUEUE_ENQUEUED 0x1ull
+#endif
 
-       fp->f_flag = FREAD | FWRITE;
-       fp->f_type = DTYPE_KQUEUE;
-       fp->f_ops = &kqueueops;
-       fp->f_data = (caddr_t)kq;
+static inline void
+filt_wllock(struct kqworkloop *kqwl)
+{
+       lck_mtx_lock(&kqwl->kqwl_statelock);
+}
 
-       proc_fdlock(p);
-       procfdtbl_releasefd(p, fd, NULL);
-       fp_drop(p, fd, fp, 1);
-       proc_fdunlock(p);
+static inline void
+filt_wlunlock(struct kqworkloop *kqwl)
+{
+       lck_mtx_unlock(&kqwl->kqwl_statelock);
+}
 
-       *retval = fd;
-       return (error);
+static inline void
+filt_wlheld(__assert_only struct kqworkloop *kqwl)
+{
+       LCK_MTX_ASSERT(&kqwl->kqwl_statelock, LCK_MTX_ASSERT_OWNED);
 }
 
-static int
-kevent_copyin(user_addr_t *addrp, struct kevent64_s *kevp, struct proc *p, int iskev64)
+#define WL_OWNER_SUSPENDED    ((thread_t)(~0ull))  /* special owner when suspended */
+
+static inline bool
+filt_wlowner_is_valid(thread_t owner)
 {
-       int advance;
-       int error;
+       return owner != THREAD_NULL && owner != WL_OWNER_SUSPENDED;
+}
 
-       if (iskev64) {
-               advance = sizeof(struct kevent64_s);
-               error = copyin(*addrp, (caddr_t)kevp, advance);
-       } else if (IS_64BIT_PROCESS(p)) {
-               struct user64_kevent kev64;
-               bzero(kevp, sizeof(struct kevent64_s));
+static inline bool
+filt_wlshould_end_ownership(struct kqworkloop *kqwl,
+               struct kevent_internal_s *kev, int error)
+{
+       thread_t owner = kqwl->kqwl_owner;
+       return (error == 0 || error == ESTALE) &&
+                       (kev->fflags & NOTE_WL_END_OWNERSHIP) &&
+                       (owner == current_thread() || owner == WL_OWNER_SUSPENDED);
+}
 
-               advance = sizeof(kev64);
-               error = copyin(*addrp, (caddr_t)&kev64, advance);
-               if (error)
-                       return error;
-               kevp->ident = kev64.ident;
-               kevp->filter = kev64.filter;
-               kevp->flags = kev64.flags;
-               kevp->fflags = kev64.fflags;
-               kevp->data = kev64.data;
-               kevp->udata = kev64.udata;
-       } else {
-               struct user32_kevent kev32;
-               bzero(kevp, sizeof(struct kevent64_s));
+static inline bool
+filt_wlshould_update_ownership(struct kevent_internal_s *kev, int error)
+{
+       return error == 0 && (kev->fflags & NOTE_WL_DISCOVER_OWNER) &&
+                       kev->ext[EV_EXTIDX_WL_ADDR];
+}
 
-               advance = sizeof(kev32);
-               error = copyin(*addrp, (caddr_t)&kev32, advance);
-               if (error)
-                       return error;
-               kevp->ident = (uintptr_t)kev32.ident;
-               kevp->filter = kev32.filter;
-               kevp->flags = kev32.flags;
-               kevp->fflags = kev32.fflags;
-               kevp->data = (intptr_t)kev32.data;
-               kevp->udata = CAST_USER_ADDR_T(kev32.udata);
+static inline bool
+filt_wlshould_set_async_qos(struct kevent_internal_s *kev, int error,
+               kq_index_t async_qos)
+{
+       if (error != 0) {
+               return false;
        }
-       if (!error)
-               *addrp += advance;
-       return error;
+       if (async_qos != THREAD_QOS_UNSPECIFIED) {
+               return true;
+       }
+       if ((kev->fflags & NOTE_WL_THREAD_REQUEST) && (kev->flags & EV_DELETE)) {
+               /* see filt_wlprocess() */
+               return true;
+       }
+       return false;
 }
 
+__result_use_check
 static int
-kevent_copyout(struct kevent64_s *kevp, user_addr_t *addrp, struct proc *p, int iskev64)
+filt_wlupdateowner(struct kqworkloop *kqwl, struct kevent_internal_s *kev,
+               int error, kq_index_t async_qos)
 {
-       int advance;
-       int error;
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       thread_t cur_owner, new_owner, extra_thread_ref = THREAD_NULL;
+       kq_index_t cur_override = THREAD_QOS_UNSPECIFIED;
+       kq_index_t old_owner_override = THREAD_QOS_UNSPECIFIED;
+       boolean_t ipc_override_is_sync = false;
+       boolean_t old_owner_override_is_sync = false;
+       int action = KQWL_UTQ_NONE;
 
-       if (iskev64) {
-               advance = sizeof(struct kevent64_s);
-               error = copyout((caddr_t)kevp, *addrp, advance);
-       } else if (IS_64BIT_PROCESS(p)) {
-               struct user64_kevent kev64;
+       filt_wlheld(kqwl);
 
+       /*
+        * The owner is only changed under both the filt_wllock and the
+        * kqwl_req_lock. Looking at it with either one held is fine.
+        */
+       cur_owner = kqwl->kqwl_owner;
+       if (filt_wlshould_end_ownership(kqwl, kev, error)) {
+               new_owner = THREAD_NULL;
+       } else if (filt_wlshould_update_ownership(kev, error)) {
                /*
-                * deal with the special case of a user-supplied
-                * value of (uintptr_t)-1.
+                * Decipher the owner port name, and translate accordingly.
+                * The low 2 bits were borrowed for other flags, so mask them off.
                 */
-               kev64.ident = (kevp->ident == (uintptr_t)-1) ?
-                          (uint64_t)-1LL : (uint64_t)kevp->ident;
+               uint64_t udata = kev->ext[EV_EXTIDX_WL_VALUE];
+               mach_port_name_t new_owner_name = (mach_port_name_t)udata & ~0x3;
+               if (new_owner_name != MACH_PORT_NULL) {
+                       new_owner_name = ipc_entry_name_mask(new_owner_name);
+               }
 
-               kev64.filter = kevp->filter;
-               kev64.flags = kevp->flags;
-               kev64.fflags = kevp->fflags;
-               kev64.data = (int64_t) kevp->data;
-               kev64.udata = kevp->udata;
-               advance = sizeof(kev64);
-               error = copyout((caddr_t)&kev64, *addrp, advance);
+               if (MACH_PORT_VALID(new_owner_name)) {
+                       new_owner = port_name_to_thread(new_owner_name);
+                       if (new_owner == THREAD_NULL)
+                               return EOWNERDEAD;
+                       extra_thread_ref = new_owner;
+               } else if (new_owner_name == MACH_PORT_DEAD) {
+                       new_owner = WL_OWNER_SUSPENDED;
+               } else {
+                       /*
+                        * We never want to learn a new owner that is NULL.
+                        * Ownership should be ended with END_OWNERSHIP.
+                        */
+                       new_owner = cur_owner;
+               }
        } else {
-               struct user32_kevent kev32;
+               new_owner = cur_owner;
+       }
 
-               kev32.ident = (uint32_t)kevp->ident;
-               kev32.filter = kevp->filter;
-               kev32.flags = kevp->flags;
-               kev32.fflags = kevp->fflags;
-               kev32.data = (int32_t)kevp->data;
-               kev32.udata = kevp->udata;
-               advance = sizeof(kev32);
-               error = copyout((caddr_t)&kev32, *addrp, advance);
+       if (filt_wlshould_set_async_qos(kev, error, async_qos)) {
+               action = KQWL_UTQ_SET_ASYNC_QOS;
+       }
+       if (cur_owner == new_owner && action == KQWL_UTQ_NONE) {
+               goto out;
+       }
+
+       kqwl_req_lock(kqwl);
+
+       /* If already tracked as servicer, don't track as owner */
+       if ((kqr->kqr_state & KQR_BOUND) && new_owner == kqr->kqr_thread) {
+               kqwl->kqwl_owner = new_owner = THREAD_NULL;
+       }
+
+       if (cur_owner != new_owner) {
+               kqwl->kqwl_owner = new_owner;
+               if (new_owner == extra_thread_ref) {
+                       /* we just transfered this ref to kqwl_owner */
+                       extra_thread_ref = THREAD_NULL;
+               }
+               cur_override = kqworkloop_combined_qos(kqwl, &ipc_override_is_sync);
+               old_owner_override = kqr->kqr_dsync_owner_qos;
+               old_owner_override_is_sync = kqr->kqr_owner_override_is_sync;
+
+               if (filt_wlowner_is_valid(new_owner)) {
+                       /* override it before we drop the old */
+                       if (cur_override != THREAD_QOS_UNSPECIFIED) {
+                               thread_add_ipc_override(new_owner, cur_override);
+                       }
+                       if (ipc_override_is_sync) {
+                               thread_add_sync_ipc_override(new_owner);
+                       }
+                       /* Update the kqr to indicate that owner has sync ipc override */
+                       kqr->kqr_dsync_owner_qos = cur_override;
+                       kqr->kqr_owner_override_is_sync = ipc_override_is_sync;
+                       thread_starts_owning_workloop(new_owner);
+                       if ((kqr->kqr_state & (KQR_THREQUESTED | KQR_BOUND)) == KQR_THREQUESTED) {
+                               if (action == KQWL_UTQ_NONE) {
+                                       action = KQWL_UTQ_REDRIVE_EVENTS;
+                               }
+                       }
+               } else if (new_owner == THREAD_NULL) {
+                       kqr->kqr_dsync_owner_qos = THREAD_QOS_UNSPECIFIED;
+                       kqr->kqr_owner_override_is_sync = false;
+                       if ((kqr->kqr_state & (KQR_THREQUESTED | KQR_WAKEUP)) == KQR_WAKEUP) {
+                               if (action == KQWL_UTQ_NONE) {
+                                       action = KQWL_UTQ_REDRIVE_EVENTS;
+                               }
+                       }
+               }
+       }
+
+       if (action != KQWL_UTQ_NONE) {
+               kqworkloop_update_threads_qos(kqwl, action, async_qos);
+       }
+
+       kqwl_req_unlock(kqwl);
+
+       /* Now that we are unlocked, drop the override and ref on old owner */
+       if (new_owner != cur_owner && filt_wlowner_is_valid(cur_owner)) {
+               if (old_owner_override != THREAD_QOS_UNSPECIFIED) {
+                       thread_drop_ipc_override(cur_owner);
+               }
+               if (old_owner_override_is_sync) {
+                       thread_drop_sync_ipc_override(cur_owner);
+               }
+               thread_ends_owning_workloop(cur_owner);
+               thread_deallocate(cur_owner);
+       }
+
+out:
+       if (extra_thread_ref) {
+               thread_deallocate(extra_thread_ref);
        }
-       if (!error)
-               *addrp += advance;
        return error;
 }
 
-/*
- * kevent_continue - continue a kevent syscall after blocking
- *
- *     assume we inherit a use count on the kq fileglob.
- */
-
-static void
-kevent_continue(__unused struct kqueue *kq, void *data, int error)
+static int
+filt_wldebounce(
+       struct kqworkloop *kqwl,
+       struct kevent_internal_s *kev,
+       int default_result)
 {
-       struct _kevent *cont_args;
-       struct fileproc *fp;
-       int32_t *retval;
-       int noutputs;
-       int fd;
-       struct proc *p = current_proc();
+       user_addr_t addr = CAST_USER_ADDR_T(kev->ext[EV_EXTIDX_WL_ADDR]);
+       uint64_t udata;
+       int error;
 
-       cont_args = (struct _kevent *)data;
-       noutputs = cont_args->eventout;
-       retval = cont_args->retval;
-       fd = cont_args->fd;
-       fp = cont_args->fp;
+       /* we must have the workloop state mutex held */
+       filt_wlheld(kqwl);
 
-       fp_drop(p, fd, fp, 0);
+       /* Do we have a debounce address to work with? */
+       if (addr) {
+               uint64_t kdata = kev->ext[EV_EXTIDX_WL_VALUE];
+               uint64_t mask = kev->ext[EV_EXTIDX_WL_MASK];
 
-       /* don't restart after signals... */
-       if (error == ERESTART)
-               error = EINTR;
-       else if (error == EWOULDBLOCK)
-               error = 0;
-       if (error == 0)
-               *retval = noutputs;
-       unix_syscall_return(error);
+               error = copyin_word(addr, &udata, sizeof(udata));
+               if (error) {
+                       return error;
+               }
+
+               /* update state as copied in */
+               kev->ext[EV_EXTIDX_WL_VALUE] = udata;
+
+               /* If the masked bits don't match, reject it as stale */
+               if ((udata & mask) != (kdata & mask)) {
+                       return ESTALE;
+               }
+
+#if DEBUG || DEVELOPMENT
+               if ((kev->fflags & NOTE_WL_THREAD_REQUEST) && !(kev->flags & EV_DELETE)) {
+                       if ((udata & DISPATCH_QUEUE_ENQUEUED) == 0 &&
+                                       (udata >> 48) != 0 && (udata >> 48) != 0xffff) {
+                               panic("kevent: workloop %#016llx is not enqueued "
+                                               "(kev:%p dq_state:%#016llx)", kev->udata, kev, udata);
+                       }
+               }
+#endif
+       }
+
+       return default_result;
 }
 
 /*
- * kevent - [syscall] register and wait for kernel events
- *
+ * Remembers the last updated that came in from userspace for debugging reasons.
+ * - fflags is mirrored from the userspace kevent
+ * - ext[i, i != VALUE] is mirrored from the userspace kevent
+ * - ext[VALUE] is set to what the kernel loaded atomically
+ * - data is set to the error if any
  */
-int
-kevent(struct proc *p, struct kevent_args *uap, int32_t *retval)
+static inline void
+filt_wlremember_last_update(
+       __assert_only struct kqworkloop *kqwl,
+       struct knote *kn,
+       struct kevent_internal_s *kev,
+       int error)
 {
-       return kevent_internal(p, 
-                       0, 
-                       uap->changelist,
-                       uap->nchanges,
-                       uap->eventlist,
-                       uap->nevents,
-                       uap->fd,
-                       uap->timeout,
-                       0, /* no flags from old kevent() call */
-                       retval);
-}
-  
-int
-kevent64(struct proc *p, struct kevent64_args *uap, int32_t *retval)
+       filt_wlheld(kqwl);
+       kn->kn_fflags = kev->fflags;
+       kn->kn_data = error;
+       memcpy(kn->kn_ext, kev->ext, sizeof(kev->ext));
+}
+
+/*
+ * Return which operations on EVFILT_WORKLOOP need to be protected against
+ * knoteusewait() causing priority inversions.
+ */
+static bool
+filt_wlneeds_boost(struct kevent_internal_s *kev)
 {
-       return kevent_internal(p, 
-                       1, 
-                       uap->changelist,
-                       uap->nchanges,
-                       uap->eventlist,
-                       uap->nevents,
-                       uap->fd,
-                       uap->timeout,
-                       uap->flags,
-                       retval);
+       if (kev == NULL) {
+               /*
+                * this is an f_process() usecount, and it can cause a drop to wait
+                */
+               return true;
+       }
+       if (kev->fflags & NOTE_WL_THREAD_REQUEST) {
+               /*
+                * All operations on thread requests may starve drops or re-attach of
+                * the same knote, all of them need boosts. None of what we do under
+                * thread-request usecount holds blocks anyway.
+                */
+               return true;
+       }
+       if (kev->fflags & NOTE_WL_SYNC_WAIT) {
+               /*
+                * this may call filt_wlwait() and we don't want to hold any boost when
+                * woken up, this would cause background threads contending on
+                * dispatch_sync() to wake up at 64 and be preempted immediately when
+                * this drops.
+                */
+               return false;
+       }
+
+       /*
+        * SYNC_WAIT knotes when deleted don't need to be rushed, there's no
+        * detach/reattach race with these ever. In addition to this, when the
+        * SYNC_WAIT knote is dropped, the caller is no longer receiving the
+        * workloop overrides if any, and we'd rather schedule other threads than
+        * him, he's not possibly stalling anything anymore.
+        */
+       return (kev->flags & EV_DELETE) == 0;
 }
 
 static int
-kevent_internal(struct proc *p, int iskev64, user_addr_t changelist, 
-               int nchanges, user_addr_t ueventlist, int nevents, int fd, 
-               user_addr_t utimeout, __unused unsigned int flags, 
-               int32_t *retval)
+filt_wlattach(struct knote *kn, struct kevent_internal_s *kev)
 {
-       struct _kevent *cont_args;
-       uthread_t ut;
-       struct kqueue *kq;
-       struct fileproc *fp;
-       struct kevent64_s kev;
-       int error, noutputs;
-       struct timeval atv;
+       struct kqueue *kq = knote_get_kq(kn);
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       int error = 0;
+       kq_index_t qos_index = 0;
 
-       /* convert timeout to absolute - if we have one */
-       if (utimeout != USER_ADDR_NULL) {
-               struct timeval rtv;
-               if (IS_64BIT_PROCESS(p)) {
-                       struct user64_timespec ts;
-                       error = copyin(utimeout, &ts, sizeof(ts));
-                       if ((ts.tv_sec & 0xFFFFFFFF00000000ull) != 0)
-                               error = EINVAL;
-                       else
-                               TIMESPEC_TO_TIMEVAL(&rtv, &ts);
+       if ((kq->kq_state & KQ_WORKLOOP) == 0) {
+               error = ENOTSUP;
+               goto out;
+       }
+
+#if DEVELOPMENT || DEBUG
+       if (kev->ident == 0 && kev->udata == 0 && kev->fflags == 0) {
+               struct kqrequest *kqr = &kqwl->kqwl_request;
+
+               kqwl_req_lock(kqwl);
+               kev->fflags = 0;
+               if (kqr->kqr_dsync_waiters) {
+                       kev->fflags |= NOTE_WL_SYNC_WAIT;
+               }
+               if (kqr->kqr_qos_index) {
+                       kev->fflags |= NOTE_WL_THREAD_REQUEST;
+               }
+               if (kqwl->kqwl_owner == WL_OWNER_SUSPENDED) {
+                       kev->ext[0] = ~0ull;
                } else {
-                       struct user32_timespec ts;
-                       error = copyin(utimeout, &ts, sizeof(ts));
-                       TIMESPEC_TO_TIMEVAL(&rtv, &ts);
+                       kev->ext[0] = thread_tid(kqwl->kqwl_owner);
                }
-               if (error)
-                       return error;
-               if (itimerfix(&rtv))
-                       return EINVAL;
-               getmicrouptime(&atv);
-               timevaladd(&atv, &rtv);
-       } else {
-               atv.tv_sec = 0;
-               atv.tv_usec = 0;
+               kev->ext[1] = thread_tid(kqwl->kqwl_request.kqr_thread);
+               kev->ext[2] = thread_owned_workloops_count(current_thread());
+               kev->ext[3] = kn->kn_kevent.ext[3];
+               kqwl_req_unlock(kqwl);
+               error = EBUSY;
+               goto out;
        }
+#endif
 
-       /* get a usecount for the kq itself */
-       if ((error = fp_getfkq(p, fd, &fp, &kq)) != 0)
-               return(error);
-       
-       /* each kq should only be used for events of one type */
-       kqlock(kq);
-       if (kq->kq_state & (KQ_KEV32 | KQ_KEV64)) {
-               if (((iskev64 && (kq->kq_state & KQ_KEV32)) ||
-                       (!iskev64 && (kq->kq_state & KQ_KEV64)))) {
+       /* Some simple validation */
+       int command = (kn->kn_sfflags & NOTE_WL_COMMANDS_MASK);
+       switch (command) {
+       case NOTE_WL_THREAD_REQUEST:
+               if (kn->kn_id != kqwl->kqwl_dynamicid) {
                        error = EINVAL;
-                       kqunlock(kq);
-                       goto errorout;
+                       goto out;
+               }
+               qos_index = qos_index_from_qos(kn, kn->kn_qos, FALSE);
+               if (qos_index < THREAD_QOS_MAINTENANCE ||
+                               qos_index > THREAD_QOS_USER_INTERACTIVE) {
+                       error = ERANGE;
+                       goto out;
+               }
+               break;
+       case NOTE_WL_SYNC_WAIT:
+       case NOTE_WL_SYNC_WAKE:
+               if (kq->kq_state & KQ_NO_WQ_THREAD) {
+                       error = ENOTSUP;
+                       goto out;
+               }
+               if (kn->kn_id == kqwl->kqwl_dynamicid) {
+                       error = EINVAL;
+                       goto out;
+               }
+               if ((kn->kn_flags & EV_DISABLE) == 0) {
+                       error = EINVAL;
+                       goto out;
+               }
+               if (kn->kn_sfflags & NOTE_WL_END_OWNERSHIP) {
+                       error = EINVAL;
+                       goto out;
                }
+               break;
+       default:
+               error = EINVAL;
+               goto out;
+       }
+
+       filt_wllock(kqwl);
+       kn->kn_hook = NULL;
+
+       if (command == NOTE_WL_THREAD_REQUEST && kqwl->kqwl_request.kqr_qos_index) {
+               /*
+                * There already is a thread request, and well, you're only allowed
+                * one per workloop, so fail the attach.
+                *
+                * Note: kqr_qos_index is always set with the wllock held, so we
+                * don't need to take the kqr lock.
+                */
+               error = EALREADY;
        } else {
-               kq->kq_state |= (iskev64 ? KQ_KEV64 : KQ_KEV32);
+               /* Make sure user and kernel are in agreement on important state */
+               error = filt_wldebounce(kqwl, kev, 0);
        }
-       kqunlock(kq);
 
-       /* register all the change requests the user provided... */
-       noutputs = 0;
-       while (nchanges > 0 && error == 0) {
-               error = kevent_copyin(&changelist, &kev, p, iskev64);
-               if (error)
-                       break;
-                               
-               kev.flags &= ~EV_SYSFLAGS;
-               error = kevent_register(kq, &kev, p);
-               if ((error || (kev.flags & EV_RECEIPT)) && nevents > 0) {
-                       kev.flags = EV_ERROR;
-                       kev.data = error;
-                       error = kevent_copyout(&kev, &ueventlist, p, iskev64);
-                       if (error == 0) {
-                               nevents--;
-                               noutputs++;
-                       }
+       error = filt_wlupdateowner(kqwl, kev, error, qos_index);
+       filt_wlunlock(kqwl);
+out:
+       if (error) {
+               kn->kn_flags |= EV_ERROR;
+               /* If userland wants ESTALE to be hidden, fail the attach anyway */
+               if (error == ESTALE && (kn->kn_sfflags & NOTE_WL_IGNORE_ESTALE)) {
+                       error = 0;
                }
-               nchanges--;
+               kn->kn_data = error;
+               return 0;
        }
 
-       /* store the continuation/completion data in the uthread */
-       ut = (uthread_t)get_bsdthread_info(current_thread());
-       cont_args = &ut->uu_kevent.ss_kevent;
-       cont_args->fp = fp;
-       cont_args->fd = fd;
-       cont_args->retval = retval;
-       cont_args->eventlist = ueventlist;
-       cont_args->eventcount = nevents;
-       cont_args->eventout = noutputs;
-       cont_args->eventsize = iskev64;
-
-       if (nevents > 0 && noutputs == 0 && error == 0)
-               error = kqueue_scan(kq, kevent_callback,
-                                   kevent_continue, cont_args,
-                                   &atv, p);
-       kevent_continue(kq, cont_args, error);
-
-errorout:
-       fp_drop(p, fd, fp, 0);
-       return error;
+       /* Just attaching the thread request successfully will fire it */
+       return command == NOTE_WL_THREAD_REQUEST;
 }
 
-
-/*
- * kevent_callback - callback for each individual event
- *
- *     called with nothing locked
- *     caller holds a reference on the kqueue
- */
-
+__attribute__((noinline,not_tail_called))
 static int
-kevent_callback(__unused struct kqueue *kq, struct kevent64_s *kevp, 
-               void *data)
+filt_wlwait(struct kqworkloop           *kqwl,
+            struct knote                *kn,
+            struct kevent_internal_s    *kev)
 {
-       struct _kevent *cont_args;
-       int error;
-       int iskev64;
-
-       cont_args = (struct _kevent *)data;
-       assert(cont_args->eventout < cont_args->eventcount);
-
-       iskev64 = cont_args->eventsize;
-
-       /*
-        * Copy out the appropriate amount of event data for this user.
-        */
-       error = kevent_copyout(kevp, &cont_args->eventlist, current_proc(), iskev64);
+       filt_wlheld(kqwl);
+       assert((kn->kn_sfflags & NOTE_WL_SYNC_WAKE) == 0);
 
        /*
-        * If there isn't space for additional events, return
-        * a harmless error to stop the processing here
+        * Hint to the wakeup side that this thread is waiting.  Also used by
+        * stackshot for waitinfo.
         */
-       if (error == 0 && ++cont_args->eventout == cont_args->eventcount)
-                       error = EWOULDBLOCK;
-       return error;
-}
+       kn->kn_hook = current_thread();
 
-/*
- * kevent_description - format a description of a kevent for diagnostic output
- *
- *      called with a 128-byte string buffer
- */
+       thread_set_pending_block_hint(current_thread(), kThreadWaitWorkloopSyncWait);
 
-char *
-kevent_description(struct kevent64_s *kevp, char *s, size_t n)
-{
-        snprintf(s, n,
-                 "kevent="
-                 "{.ident=%#llx, .filter=%d, .flags=%#x, .fflags=%#x, .data=%#llx, .udata=%#llx, .ext[0]=%#llx, .ext[1]=%#llx}",
-                 kevp->ident,
-                 kevp->filter,
-                 kevp->flags,
-                 kevp->fflags,
-                 kevp->data,
-                 kevp->udata,
-                kevp->ext[0],
-                kevp->ext[1]);
-        return s;
-}
+       wait_result_t wr = assert_wait(kn, THREAD_ABORTSAFE);
 
-/*
- * kevent_register - add a new event to a kqueue
- *
- *     Creates a mapping between the event source and
- *     the kqueue via a knote data structure.
- *
- *     Because many/most the event sources are file
- *     descriptor related, the knote is linked off
- *     the filedescriptor table for quick access.
- *
- *     called with nothing locked
- *     caller holds a reference on the kqueue
- */
+       if (wr == THREAD_WAITING) {
+               kq_index_t qos_index = qos_index_from_qos(kn, kev->qos, TRUE);
+               struct kqrequest *kqr = &kqwl->kqwl_request;
 
-int
-kevent_register(struct kqueue *kq, struct kevent64_s *kev, __unused struct proc *ctxp)
-{
-       struct proc *p = kq->kq_p;
-       struct filedesc *fdp = p->p_fd;
-       struct filterops *fops;
-       struct fileproc *fp = NULL;
-       struct knote *kn = NULL;
-       int error = 0;
+               thread_t thread_to_handoff = THREAD_NULL; /* holds +1 thread ref */
 
-       if (kev->filter < 0) {
-               if (kev->filter + EVFILT_SYSCOUNT < 0)
-                       return (EINVAL);
-               fops = sysfilt_ops[~kev->filter];       /* to 0-base index */
-       } else {
-               /*
-                * XXX
-                * filter attach routine is responsible for insuring that
-                * the identifier can be attached to it.
-                */
-               printf("unknown filter: %d\n", kev->filter);
-               return (EINVAL);
-       }
+               thread_t kqwl_owner = kqwl->kqwl_owner;
+               if (filt_wlowner_is_valid(kqwl_owner)) {
+                       thread_reference(kqwl_owner);
+                       thread_to_handoff = kqwl_owner;
+               }
 
- restart:
-       /* this iocount needs to be dropped if it is not registered */
-       proc_fdlock(p);
-       if (fops->f_isfd && (error = fp_lookup(p, kev->ident, &fp, 1)) != 0) {
-               proc_fdunlock(p);
-               return(error);
-       }
+               kqwl_req_lock(kqwl);
 
-       if (fops->f_isfd) {
-               /* fd-based knotes are linked off the fd table */
-               if (kev->ident < (u_int)fdp->fd_knlistsize) {
-                       SLIST_FOREACH(kn, &fdp->fd_knlist[kev->ident], kn_link)
-                               if (kq == kn->kn_kq &&
-                                   kev->filter == kn->kn_filter)
-                                       break;
-               }
-       } else {
-               /* hash non-fd knotes here too */
-               if (fdp->fd_knhashmask != 0) {
-                       struct klist *list;
-                       
-                       list = &fdp->fd_knhash[
-                           KN_HASH((u_long)kev->ident, fdp->fd_knhashmask)];
-                       SLIST_FOREACH(kn, list, kn_link)
-                               if (kev->ident == kn->kn_id &&
-                                   kq == kn->kn_kq &&
-                                   kev->filter == kn->kn_filter)
-                                       break;
+               if (qos_index) {
+                       assert(kqr->kqr_dsync_waiters < UINT16_MAX);
+                       kqr->kqr_dsync_waiters++;
+                       if (qos_index > kqr->kqr_dsync_waiters_qos) {
+                               kqworkloop_update_threads_qos(kqwl,
+                                               KQWL_UTQ_SET_SYNC_WAITERS_QOS, qos_index);
+                       }
                }
-       }
 
-       /*
-        * kn now contains the matching knote, or NULL if no match
-        */
-       if (kn == NULL) {
-               if ((kev->flags & (EV_ADD|EV_DELETE)) == EV_ADD) {
-                       kn = knote_alloc();
-                       if (kn == NULL) {
-                               proc_fdunlock(p);
-                               error = ENOMEM;
-                               goto done;
-                       }
-                       kn->kn_fp = fp;
-                       kn->kn_kq = kq;
-                       kn->kn_tq = &kq->kq_head;
-                       kn->kn_fop = fops;
-                       kn->kn_sfflags = kev->fflags;
-                       kn->kn_sdata = kev->data;
-                       kev->fflags = 0;
-                       kev->data = 0;
-                       kn->kn_kevent = *kev;
-                       kn->kn_inuse = 1;  /* for f_attach() */
-                       kn->kn_status = KN_ATTACHING;
+               if ((kqr->kqr_state & KQR_BOUND) && thread_to_handoff == THREAD_NULL) {
+                       assert(kqr->kqr_thread != THREAD_NULL);
+                       thread_t servicer = kqr->kqr_thread;
 
-                       /* before anyone can find it */
-                       if (kev->flags & EV_DISABLE)
-                               kn->kn_status |= KN_DISABLED;
+                       thread_reference(servicer);
+                       thread_to_handoff = servicer;
+               }
 
-                       error = knote_fdpattach(kn, fdp, p);
-                       proc_fdunlock(p);
+               kqwl_req_unlock(kqwl);
 
-                       if (error) {
-                               knote_free(kn);
-                               goto done;
-                       }
+               filt_wlunlock(kqwl);
 
-                       /*
-                        * apply reference count to knote structure, and
-                        * do not release it at the end of this routine.
-                        */
-                       fp = NULL;
+               /* TODO: use continuation based blocking <rdar://problem/31299584> */
 
-                       error = fops->f_attach(kn);
+               /* consume a refcount on thread_to_handoff, then thread_block() */
+               wr = thread_handoff(thread_to_handoff);
+               thread_to_handoff = THREAD_NULL;
 
-                       kqlock(kq);
+               filt_wllock(kqwl);
 
-                       if (error != 0) {
-                               /*
-                                * Failed to attach correctly, so drop.
-                                * All other possible users/droppers
-                                * have deferred to us.
-                                */
-                               kn->kn_status |= KN_DROPPING;
-                               kqunlock(kq);
-                               knote_drop(kn, p);
-                               goto done;
-                       } else if (kn->kn_status & KN_DROPPING) {
-                               /*
-                                * Attach succeeded, but someone else
-                                * deferred their drop - now we have
-                                * to do it for them (after detaching).
-                                */
-                               kqunlock(kq);
-                               kn->kn_fop->f_detach(kn);
-                               knote_drop(kn, p);
-                               goto done;
-                       }
-                       kn->kn_status &= ~KN_ATTACHING;
-                       kqunlock(kq);
-               } else {
-                       proc_fdunlock(p);
-                       error = ENOENT;
-                       goto done;
-               }
-       } else {
-               /* existing knote - get kqueue lock */
-               kqlock(kq);
-               proc_fdunlock(p);
-               
-               if (kev->flags & EV_DELETE) {
-                       knote_dequeue(kn);
-                       kn->kn_status |= KN_DISABLED;
-                       if (kqlock2knotedrop(kq, kn)) {
-                               kn->kn_fop->f_detach(kn);
-                               knote_drop(kn, p);
-                       }
-                       goto done;
-               }
-                       
-               /* update status flags for existing knote */
-               if (kev->flags & EV_DISABLE) {
-                       knote_dequeue(kn);
-                       kn->kn_status |= KN_DISABLED;
-               } else if (kev->flags & EV_ENABLE) {
-                       kn->kn_status &= ~KN_DISABLED;
-                       if (kn->kn_status & KN_ACTIVE)
-                               knote_enqueue(kn);
-               }
+               /* clear waiting state (only one waiting thread - so no race) */
+               assert(kn->kn_hook == current_thread());
 
-               /*
-                * The user may change some filter values after the
-                * initial EV_ADD, but doing so will not reset any 
-                * filter which have already been triggered.
-                */
-               kn->kn_kevent.udata = kev->udata;
-               if (fops->f_isfd || fops->f_touch == NULL) {
-                       kn->kn_sfflags = kev->fflags;
-                       kn->kn_sdata = kev->data;
+               if (qos_index) {
+                       kqwl_req_lock(kqwl);
+                       assert(kqr->kqr_dsync_waiters > 0);
+                       if (--kqr->kqr_dsync_waiters == 0) {
+                               assert(kqr->kqr_dsync_waiters_qos);
+                               kqworkloop_update_threads_qos(kqwl,
+                                               KQWL_UTQ_SET_SYNC_WAITERS_QOS, 0);
+                       }
+                       kqwl_req_unlock(kqwl);
                }
+       }
 
-               /*
-                * If somebody is in the middle of dropping this
-                * knote - go find/insert a new one.  But we have
-                * wait for this one to go away first. Attaches
-                * running in parallel may also drop/modify the
-                * knote.  Wait for those to complete as well and
-                * then start over if we encounter one.
-                */
-               if (!kqlock2knoteusewait(kq, kn)) {
-                       /* kqueue, proc_fdlock both unlocked */
-                       goto restart;
-               }
+       kn->kn_hook = NULL;
 
-               /*
-                * Call touch routine to notify filter of changes
-                * in filter values.
-                */
-               if (!fops->f_isfd && fops->f_touch != NULL)
-                       fops->f_touch(kn, kev, EVENT_REGISTER);
+       switch (wr) {
+       case THREAD_AWAKENED:
+               return 0;
+       case THREAD_INTERRUPTED:
+               return EINTR;
+       case THREAD_RESTART:
+               return ECANCELED;
+       default:
+               panic("filt_wlattach: unexpected wait result %d", wr);
+               return EINVAL;
        }
-       /* still have use ref on knote */
+}
 
-       /*
-        * If the knote is not marked to always stay enqueued,
-        * invoke the filter routine to see if it should be
-        * enqueued now.
-        */
-       if ((kn->kn_status & KN_STAYQUEUED) == 0 && kn->kn_fop->f_event(kn, 0)) {
-               if (knoteuse2kqlock(kq, kn))
-                       knote_activate(kn, 1);
-               kqunlock(kq);
-       } else {
-               knote_put(kn);
-       }
+/* called in stackshot context to report the thread responsible for blocking this thread */
+void
+kdp_workloop_sync_wait_find_owner(__assert_only thread_t thread,
+                                  event64_t event,
+                                  thread_waitinfo_t *waitinfo)
+{
+       struct knote *kn = (struct knote*) event;
+       assert(kdp_is_in_zone(kn, "knote zone"));
 
-done:
-       if (fp != NULL)
-               fp_drop(p, kev->ident, fp, 0);
-       return (error);
-}
+       assert(kn->kn_hook == thread);
 
+       struct kqueue *kq = knote_get_kq(kn);
+       assert(kdp_is_in_zone(kq, "kqueue workloop zone"));
+       assert(kq->kq_state & KQ_WORKLOOP);
 
-/*
- * knote_process - process a triggered event
- *
- *     Validate that it is really still a triggered event
- *     by calling the filter routines (if necessary).  Hold
- *     a use reference on the knote to avoid it being detached.
- *     If it is still considered triggered, invoke the callback
- *     routine provided and move it to the provided inprocess
- *     queue.
- *
- *     caller holds a reference on the kqueue.
- *     kqueue locked on entry and exit - but may be dropped
- */
-static int
-knote_process(struct knote     *kn,
-             kevent_callback_t callback,
-             void              *data, 
-             struct kqtailq    *inprocessp, 
-             struct proc       *p)
-{
-       struct kqueue *kq = kn->kn_kq;
-       struct kevent64_s kev;
-       int touch;
-       int result;
-       int error;
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       struct kqrequest *kqr = &kqwl->kqwl_request;
 
-       /*
-        * Determine the kevent state we want to return.
-        *
-        * Some event states need to be revalidated before returning
-        * them, others we take the snapshot at the time the event
-        * was enqueued.
-        *
-        * Events with non-NULL f_touch operations must be touched.
-        * Triggered events must fill in kev for the callback.
-        *
-        * Convert our lock to a use-count and call the event's
-        * filter routine(s) to update.
-        */
-       if ((kn->kn_status & KN_DISABLED) != 0) {
-               result = 0;
-               touch = 0;
-       } else {
-               int revalidate;
+       thread_t kqwl_owner = kqwl->kqwl_owner;
+       thread_t servicer = kqr->kqr_thread;
 
-               result = 1;
-               revalidate = ((kn->kn_status & KN_STAYQUEUED) != 0 ||
-                             (kn->kn_flags & EV_ONESHOT) == 0);
-               touch = (!kn->kn_fop->f_isfd && kn->kn_fop->f_touch != NULL);
+       if (kqwl_owner == WL_OWNER_SUSPENDED) {
+               waitinfo->owner = STACKSHOT_WAITOWNER_SUSPENDED;
+       } else if (kqwl_owner != THREAD_NULL) {
+               assert(kdp_is_in_zone(kqwl_owner, "threads"));
 
-               if (revalidate || touch) {
-                       if (revalidate)
-                               knote_deactivate(kn);
-                       
-                       /* call the filter/touch routines with just a ref */
-                       if (kqlock2knoteuse(kq, kn)) {
-                       
-                               /* if we have to revalidate, call the filter */
-                               if (revalidate) {
-                                       result = kn->kn_fop->f_event(kn, 0);
-                               }
+               waitinfo->owner = thread_tid(kqwl->kqwl_owner);
+       } else if (servicer != THREAD_NULL) {
+               assert(kdp_is_in_zone(servicer, "threads"));
 
-                               /* capture the kevent data - using touch if specified */
-                               if (result && touch) {
-                                       kn->kn_fop->f_touch(kn, &kev, EVENT_PROCESS);
-                               }
+               waitinfo->owner = thread_tid(servicer);
+       } else if (kqr->kqr_state & KQR_THREQUESTED) {
+               waitinfo->owner = STACKSHOT_WAITOWNER_THREQUESTED;
+       } else {
+               waitinfo->owner = 0;
+       }
 
-                               /* convert back to a kqlock - bail if the knote went away */
-                               if (!knoteuse2kqlock(kq, kn)) {
-                                       return EJUSTRETURN;
-                               } else if (result) {
-                                       /* if revalidated as alive, make sure it's active */
-                                       if (!(kn->kn_status & KN_ACTIVE)) {
-                                               knote_activate(kn, 0);
-                                       }
+       waitinfo->context = kqwl->kqwl_dynamicid;
 
-                                       /* capture all events that occurred during filter */
-                                       if (!touch) {
-                                               kev = kn->kn_kevent;
-                                       }
+       return;
+}
 
-                               } else if ((kn->kn_status & KN_STAYQUEUED) == 0) {
-                                       /* was already dequeued, so just bail on this one */
-                                       return EJUSTRETURN;
-                               }
-                       } else {
-                               return EJUSTRETURN;
-                       }
-               } else {
-                       kev = kn->kn_kevent;
+/*
+ * Takes kqueue locked, returns locked, may drop in the middle and/or block for a while
+ */
+static int
+filt_wlpost_attach(struct knote *kn, struct  kevent_internal_s *kev)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       int error = 0;
+
+       if (kev->fflags & NOTE_WL_SYNC_WAIT) {
+               if (kqlock2knoteuse(kq, kn, KNUSE_NONE)) {
+                       filt_wllock(kqwl);
+                       /* if the wake has already preposted, don't wait */
+                       if ((kn->kn_sfflags & NOTE_WL_SYNC_WAKE) == 0)
+                               error = filt_wlwait(kqwl, kn, kev);
+                       filt_wlunlock(kqwl);
+                       knoteuse2kqlock(kq, kn, KNUSE_NONE);
                }
        }
-               
-       /* move knote onto inprocess queue */
-       assert(kn->kn_tq == &kq->kq_head);
-       TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
-       kn->kn_tq = inprocessp;
-       TAILQ_INSERT_TAIL(inprocessp, kn, kn_tqe);
+       return error;
+}
+
+static void
+filt_wldetach(__assert_only struct knote *kn)
+{
+       assert(knote_get_kq(kn)->kq_state & KQ_WORKLOOP);
 
        /*
-        * Determine how to dispatch the knote for future event handling.
-        * not-fired: just return (do not callout).
-        * One-shot: deactivate it.
-        * Clear: deactivate and clear the state.
-        * Dispatch: don't clear state, just deactivate it and mark it disabled.
-        * All others: just leave where they are.
+        * Thread requests have nothing to detach.
+        * Sync waiters should have been aborted out
+        * and drop their refs before we could drop/
+        * detach their knotes.
         */
+       assert(kn->kn_hook == NULL);
+}
 
-       if (result == 0) {
-               return EJUSTRETURN;
-       } else if ((kn->kn_flags & EV_ONESHOT) != 0) {
-               knote_deactivate(kn);
-               if (kqlock2knotedrop(kq, kn)) {
-                       kn->kn_fop->f_detach(kn);
-                       knote_drop(kn, p);
-               }
-       } else if ((kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) != 0) {
-               if ((kn->kn_flags & EV_DISPATCH) != 0) {
-                       /* deactivate and disable all dispatch knotes */
-                       knote_deactivate(kn);
-                       kn->kn_status |= KN_DISABLED;
-               } else if (!touch || kn->kn_fflags == 0) {
-                       /* only deactivate if nothing since the touch */
-                       knote_deactivate(kn);
-               }
-               if (!touch && (kn->kn_flags & EV_CLEAR) != 0) {
-                       /* manually clear non-touch knotes */
-                       kn->kn_data = 0;
-                       kn->kn_fflags = 0;
+static int
+filt_wlevent(
+       __unused struct knote *kn,
+       __unused long hint)
+{
+       panic("filt_wlevent");
+       return 0;
+}
+
+static int
+filt_wlvalidate_kev_flags(struct knote *kn, struct kevent_internal_s *kev)
+{
+       int new_commands = kev->fflags & NOTE_WL_COMMANDS_MASK;
+       int sav_commands = kn->kn_sfflags & NOTE_WL_COMMANDS_MASK;
+       int error = 0;
+
+       switch (new_commands) {
+       case NOTE_WL_THREAD_REQUEST:
+               /* thread requests can only update themselves */
+               if (sav_commands != new_commands)
+                       error = EINVAL;
+               break;
+
+       case NOTE_WL_SYNC_WAIT:
+               if (kev->fflags & NOTE_WL_END_OWNERSHIP)
+                       error = EINVAL;
+               /* FALLTHROUGH */
+       case NOTE_WL_SYNC_WAKE:
+               /* waits and wakes can update themselves or their counterparts */
+               if (!(sav_commands & (NOTE_WL_SYNC_WAIT | NOTE_WL_SYNC_WAKE)))
+                       error = EINVAL;
+               if (kev->fflags & NOTE_WL_UPDATE_QOS)
+                       error = EINVAL;
+               if ((kev->flags & (EV_ENABLE | EV_DELETE)) == EV_ENABLE)
+                       error = EINVAL;
+               if (kev->flags & EV_DELETE) {
+                       /*
+                        * Really this is not supported: there is absolutely no reason
+                        * whatsoever to want to fail the drop of a NOTE_WL_SYNC_WAIT knote.
+                        */
+                       if (kev->ext[EV_EXTIDX_WL_ADDR] && kev->ext[EV_EXTIDX_WL_MASK]) {
+                               error = EINVAL;
+                       }
                }
-               kqunlock(kq);
-       } else {
-               /*
-                * leave on inprocess queue.  We'll
-                * move all the remaining ones back
-                * the kq queue and wakeup any
-                * waiters when we are done.
-                */
-               kqunlock(kq);
-       }
+               break;
 
-       /* callback to handle each event as we find it */
-       error = (callback)(kq, &kev, data);
-       
-       kqlock(kq);
+       default:
+               error = EINVAL;
+       }
+       if ((kev->flags & EV_DELETE) && (kev->fflags & NOTE_WL_DISCOVER_OWNER)) {
+               error = EINVAL;
+       }
        return error;
 }
 
-/*
- * Return 0 to indicate that processing should proceed,
- * -1 if there is nothing to process.
- *
- * Called with kqueue locked and returns the same way,
- * but may drop lock temporarily.
- */
 static int
-kqueue_begin_processing(struct kqueue *kq)
+filt_wltouch(
+       struct knote *kn,
+       struct kevent_internal_s *kev)
 {
-       for (;;) {
-               if (kq->kq_count == 0) {
-                       return -1;
+       struct kqueue *kq = knote_get_kq(kn);
+       int error = 0;
+       struct kqworkloop *kqwl;
+
+       assert(kq->kq_state & KQ_WORKLOOP);
+       kqwl = (struct kqworkloop *)kq;
+
+       error = filt_wlvalidate_kev_flags(kn, kev);
+       if (error) {
+               goto out;
+       }
+
+       filt_wllock(kqwl);
+
+       /* Make sure user and kernel are in agreement on important state */
+       error = filt_wldebounce(kqwl, kev, 0);
+       if (error) {
+               error = filt_wlupdateowner(kqwl, kev, error, 0);
+               goto out_unlock;
+       }
+
+       int new_command = kev->fflags & NOTE_WL_COMMANDS_MASK;
+       switch (new_command) {
+       case NOTE_WL_THREAD_REQUEST:
+               assert(kqwl->kqwl_request.kqr_qos_index != THREAD_QOS_UNSPECIFIED);
+               break;
+
+       case NOTE_WL_SYNC_WAIT:
+               /*
+                * we need to allow waiting several times on the same knote because
+                * of EINTR. If it's already woken though, it won't block.
+                */
+               break;
+
+       case NOTE_WL_SYNC_WAKE:
+               if (kn->kn_sfflags & NOTE_WL_SYNC_WAKE) {
+                       /* disallow waking the same knote twice */
+                       error = EALREADY;
+                       goto out_unlock;
                }
+               if (kn->kn_hook) {
+                       thread_wakeup_thread((event_t)kn, (thread_t)kn->kn_hook);
+               }
+               break;
 
-               /* if someone else is processing the queue, wait */
-               if (kq->kq_nprocess != 0) {
-                       wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, &kq->kq_nprocess, THREAD_UNINT, 0);
-                       kq->kq_state |= KQ_PROCWAIT;
-                       kqunlock(kq);
-                       thread_block(THREAD_CONTINUE_NULL);
+       default:
+               error = EINVAL;
+               goto out_unlock;
+       }
+
+       /*
+        * Save off any additional fflags/data we just accepted
+        * But only keep the last round of "update" bits we acted on which helps
+        * debugging a lot.
+        */
+       kn->kn_sfflags &= ~NOTE_WL_UPDATES_MASK;
+       kn->kn_sfflags |= kev->fflags;
+       kn->kn_sdata = kev->data;
+
+       kq_index_t qos_index = THREAD_QOS_UNSPECIFIED;
+
+       if (kev->fflags & NOTE_WL_UPDATE_QOS) {
+               qos_t qos = pthread_priority_canonicalize(kev->qos, FALSE);
+
+               if (kn->kn_qos != qos) {
+                       qos_index = qos_index_from_qos(kn, qos, FALSE);
+                       if (qos_index == THREAD_QOS_UNSPECIFIED) {
+                               error = ERANGE;
+                               goto out_unlock;
+                       }
                        kqlock(kq);
-               } else {
-                       kq->kq_nprocess = 1;
-                       return 0;
+                       if (kn->kn_status & KN_QUEUED) {
+                               knote_dequeue(kn);
+                               knote_set_qos_index(kn, qos_index);
+                               knote_enqueue(kn);
+                               knote_wakeup(kn);
+                       } else {
+                               knote_set_qos_index(kn, qos_index);
+                       }
+                       kn->kn_qos = qos;
+                       kqunlock(kq);
                }
        }
-}
 
-/*
- * Called with kqueue lock held.
- */
-static void
-kqueue_end_processing(struct kqueue *kq)
-{
-       kq->kq_nprocess = 0;
-       if (kq->kq_state & KQ_PROCWAIT) {
-               kq->kq_state &= ~KQ_PROCWAIT;
-               wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kq->kq_nprocess, THREAD_AWAKENED);
+       error = filt_wlupdateowner(kqwl, kev, 0, qos_index);
+       if (error) {
+               goto out_unlock;
        }
-}
 
-/*
- * kqueue_process - process the triggered events in a kqueue
- *
- *     Walk the queued knotes and validate that they are
- *     really still triggered events by calling the filter
- *     routines (if necessary).  Hold a use reference on
- *     the knote to avoid it being detached. For each event
- *     that is still considered triggered, invoke the
- *     callback routine provided.
- *
- *     caller holds a reference on the kqueue.
- *     kqueue locked on entry and exit - but may be dropped
- *     kqueue list locked (held for duration of call)
- */
+       if (new_command == NOTE_WL_SYNC_WAIT) {
+               /* if the wake has already preposted, don't wait */
+               if ((kn->kn_sfflags & NOTE_WL_SYNC_WAKE) == 0)
+                       error = filt_wlwait(kqwl, kn, kev);
+       }
+
+out_unlock:
+       filt_wlremember_last_update(kqwl, kn, kev, error);
+       filt_wlunlock(kqwl);
+out:
+       if (error) {
+               if (error == ESTALE && (kev->fflags & NOTE_WL_IGNORE_ESTALE)) {
+                       /* If userland wants ESTALE to be hidden, do not activate */
+                       return 0;
+               }
+               kev->flags |= EV_ERROR;
+               kev->data = error;
+               return 0;
+       }
+       /* Just touching the thread request successfully will fire it */
+       return new_command == NOTE_WL_THREAD_REQUEST;
+}
 
 static int
-kqueue_process(struct kqueue *kq,
-              kevent_callback_t callback,
-              void *data, 
-              int *countp,
-              struct proc *p)
+filt_wldrop_and_unlock(
+       struct knote *kn,
+       struct kevent_internal_s *kev)
 {
-        struct kqtailq inprocess;
-       struct knote *kn;
-       int nevents;
-       int error;
+       struct kqueue *kq = knote_get_kq(kn);
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       int error = 0, knoteuse_flags = KNUSE_NONE;
 
-        TAILQ_INIT(&inprocess);
+       kqlock_held(kq);
 
-       if (kqueue_begin_processing(kq) == -1) {
-               *countp = 0;
-               /* Nothing to process */
-               return 0;
+       assert(kev->flags & EV_DELETE);
+       assert(kq->kq_state & KQ_WORKLOOP);
+
+       error = filt_wlvalidate_kev_flags(kn, kev);
+       if (error) {
+               goto out;
        }
 
-       /*
-        * Clear any pre-posted status from previous runs, so we only
-        * detect events that occur during this run.
-        */
-       wait_queue_sub_clearrefs(kq->kq_wqs);
+       if (kn->kn_sfflags & NOTE_WL_THREAD_REQUEST) {
+               knoteuse_flags |= KNUSE_BOOST;
+       }
+
+       /* take a usecount to allow taking the filt_wllock */
+       if (!kqlock2knoteuse(kq, kn, knoteuse_flags)) {
+               /* knote is being dropped already */
+               error = EINPROGRESS;
+               goto out;
+       }
+
+       filt_wllock(kqwl);
 
        /*
-        * loop through the enqueued knotes, processing each one and
-        * revalidating those that need it. As they are processed,
-        * they get moved to the inprocess queue (so the loop can end).
+        * Make sure user and kernel are in agreement on important state
+        *
+        * Userland will modify bits to cause this to fail for the touch / drop
+        * race case (when a drop for a thread request quiescing comes in late after
+        * the workloop has been woken up again).
         */
-       error = 0;
-       nevents = 0;
+       error = filt_wldebounce(kqwl, kev, 0);
 
-       while (error == 0 &&
-              (kn = TAILQ_FIRST(&kq->kq_head)) != NULL) {
-               error = knote_process(kn, callback, data, &inprocess, p);
-               if (error == EJUSTRETURN)
-                       error = 0;
-               else
-                       nevents++;
+       if (!knoteuse2kqlock(kq, kn, knoteuse_flags)) {
+               /* knote is no longer alive */
+               error = EINPROGRESS;
+               goto out_unlock;
+       }
+
+       if (!error && (kn->kn_sfflags & NOTE_WL_THREAD_REQUEST) && kn->kn_inuse) {
+               /*
+                * There is a concurrent drop or touch happening, we can't resolve this,
+                * userland has to redrive.
+                *
+                * The race we're worried about here is the following:
+                *
+                *   f_touch               |  f_drop_and_unlock
+                * ------------------------+--------------------------------------------
+                *                         | kqlock()
+                *                         | kqlock2knoteuse()
+                *                         | filt_wllock()
+                *                         | debounces successfully
+                *  kqlock()               |
+                *  kqlock2knoteuse        |
+                *  filt_wllock() <BLOCKS> |
+                *                         | knoteuse2kqlock()
+                *                         | filt_wlunlock()
+                *                         | kqlock2knotedrop() <BLOCKS, WAKES f_touch>
+                *  debounces successfully |
+                *  filt_wlunlock()        |
+                *  caller WAKES f_drop    |
+                *                         | performs drop, but f_touch should have won
+                *
+                * So if the usecount is not 0 here, we need to wait for it to drop and
+                * redrive the whole logic (including looking up the knote again).
+                */
+               filt_wlunlock(kqwl);
+               knoteusewait(kq, kn);
+               return ERESTART;
        }
 
        /*
-        * With the kqueue still locked, move any knotes
-        * remaining on the inprocess queue back to the
-        * kq's queue and wake up any waiters.
+        * If error is 0 this will set kqr_qos_index to THREAD_QOS_UNSPECIFIED
+        *
+        * If error is 0 or ESTALE this may drop ownership and cause a thread
+        * request redrive, however the kqlock is held which prevents f_process() to
+        * run until we did the drop for real.
         */
-       while ((kn = TAILQ_FIRST(&inprocess)) != NULL) {
-               assert(kn->kn_tq == &inprocess);
-               TAILQ_REMOVE(&inprocess, kn, kn_tqe);
-               kn->kn_tq = &kq->kq_head;
-               TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
+       error = filt_wlupdateowner(kqwl, kev, error, 0);
+       if (error) {
+               goto out_unlock;
+       }
+
+       if ((kn->kn_sfflags & (NOTE_WL_SYNC_WAIT | NOTE_WL_SYNC_WAKE)) ==
+                       NOTE_WL_SYNC_WAIT) {
+               /*
+                * When deleting a SYNC_WAIT knote that hasn't been woken up
+                * explicitly, issue a wake up.
+                */
+               kn->kn_sfflags |= NOTE_WL_SYNC_WAKE;
+               if (kn->kn_hook) {
+                       thread_wakeup_thread((event_t)kn, (thread_t)kn->kn_hook);
+               }
        }
 
-       kqueue_end_processing(kq);
+out_unlock:
+       filt_wlremember_last_update(kqwl, kn, kev, error);
+       filt_wlunlock(kqwl);
 
-       *countp = nevents;
+out:
+       if (error == 0) {
+               /* If nothing failed, do the regular knote drop. */
+               if (kqlock2knotedrop(kq, kn)) {
+                       knote_drop(kn, current_proc());
+               } else {
+                       error = EINPROGRESS;
+               }
+       } else {
+               kqunlock(kq);
+       }
+       if (error == ESTALE && (kev->fflags & NOTE_WL_IGNORE_ESTALE)) {
+               error = 0;
+       }
+       if (error == EINPROGRESS) {
+               /*
+                * filt_wlprocess() makes sure that no event can be delivered for
+                * NOTE_WL_THREAD_REQUEST knotes once a drop is happening, and
+                * NOTE_WL_SYNC_* knotes are never fired.
+                *
+                * It means that EINPROGRESS is about a state that userland cannot
+                * observe for this filter (an event being delivered concurrently from
+                * a drop), so silence the error.
+                */
+               error = 0;
+       }
        return error;
 }
 
-
-static void
-kqueue_scan_continue(void *data, wait_result_t wait_result)
+static int
+filt_wlprocess(
+       struct knote *kn,
+       __unused struct filt_process_s *data,
+       struct kevent_internal_s *kev)
 {
-       thread_t self = current_thread();
-       uthread_t ut = (uthread_t)get_bsdthread_info(self);
-       struct _kqueue_scan * cont_args = &ut->uu_kevent.ss_kqueue_scan;
-       struct kqueue *kq = (struct kqueue *)data;
-       int error;
-       int count;
-
-       /* convert the (previous) wait_result to a proper error */
-       switch (wait_result) {
-       case THREAD_AWAKENED:
-               kqlock(kq);
-               error = kqueue_process(kq, cont_args->call, cont_args, &count, current_proc());
-               if (error == 0 && count == 0) {
-                       wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, KQ_EVENT, 
-                                              THREAD_ABORTSAFE, cont_args->deadline); 
-                       kq->kq_state |= KQ_SLEEP;
+       struct kqueue *kq = knote_get_kq(kn);
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       int rc = 0;
+
+       assert(kq->kq_state & KQ_WORKLOOP);
+
+       /* only thread requests should get here */
+       assert(kn->kn_sfflags & NOTE_WL_THREAD_REQUEST);
+       if (kn->kn_sfflags & NOTE_WL_THREAD_REQUEST) {
+               filt_wllock(kqwl);
+               assert(kqr->kqr_qos_index != THREAD_QOS_UNSPECIFIED);
+               if (kqwl->kqwl_owner) {
+                       /*
+                        * <rdar://problem/33584321> userspace sometimes due to events being
+                        * delivered but not triggering a drain session can cause a process
+                        * of the thread request knote.
+                        *
+                        * When that happens, the automatic deactivation due to process
+                        * would swallow the event, so we have to activate the knote again.
+                        */
+                       kqlock(kq);
+                       knote_activate(kn);
                        kqunlock(kq);
-                       thread_block_parameter(kqueue_scan_continue, kq);
-                       /* NOTREACHED */
+               } else if (kqr->kqr_qos_index) {
+#if DEBUG || DEVELOPMENT
+                       user_addr_t addr = CAST_USER_ADDR_T(kn->kn_ext[EV_EXTIDX_WL_ADDR]);
+                       task_t t = current_task();
+                       uint64_t val;
+                       if (addr && task_is_active(t) && !task_is_halting(t) &&
+                                       copyin_word(addr, &val, sizeof(val)) == 0 &&
+                                       val && (val & DISPATCH_QUEUE_ENQUEUED) == 0 &&
+                                       (val >> 48) != 0 && (val >> 48) != 0xffff) {
+                               panic("kevent: workloop %#016llx is not enqueued "
+                                               "(kn:%p dq_state:%#016llx kev.dq_state:%#016llx)",
+                                               kn->kn_udata, kn, val,
+                                               kn->kn_ext[EV_EXTIDX_WL_VALUE]);
+                       }
+#endif
+                       *kev = kn->kn_kevent;
+                       kev->fflags = kn->kn_sfflags;
+                       kev->data = kn->kn_sdata;
+                       kev->qos = kn->kn_qos;
+                       rc = 1;
                }
-               kqunlock(kq);
-               break;
-       case THREAD_TIMED_OUT:
-               error = EWOULDBLOCK; 
-               break;
-       case THREAD_INTERRUPTED:
-               error = EINTR;
-               break;
-       default:
-               panic("kevent_scan_cont() - invalid wait_result (%d)", wait_result);
-               error = 0;
+               filt_wlunlock(kqwl);
        }
-       
-       /* call the continuation with the results */
-       assert(cont_args->cont != NULL);
-       (cont_args->cont)(kq, cont_args->data, error);
+       return rc;
 }
 
+#pragma mark kevent / knotes
 
 /*
- * kqueue_scan - scan and wait for events in a kqueue
- *
- *     Process the triggered events in a kqueue.
- *
- *     If there are no events triggered arrange to
- *     wait for them. If the caller provided a
- *     continuation routine, then kevent_scan will
- *     also.
- *
- *     The callback routine must be valid.
- *     The caller must hold a use-count reference on the kq.
+ * JMM - placeholder for not-yet-implemented filters
  */
+static int
+filt_badattach(__unused struct knote *kn, __unused struct kevent_internal_s *kev)
+{
+       kn->kn_flags |= EV_ERROR;
+       kn->kn_data = ENOTSUP;
+       return 0;
+}
 
-int
-kqueue_scan(struct kqueue *kq, 
-           kevent_callback_t callback,
-           kqueue_continue_t continuation,
-           void *data,
-           struct timeval *atvp,
-           struct proc *p)
+struct kqueue *
+kqueue_alloc(struct proc *p, unsigned int flags)
 {
-       thread_continue_t cont = THREAD_CONTINUE_NULL;
-       uint64_t deadline;
-       int error;
-       int first;
+       struct filedesc *fdp = p->p_fd;
+       struct kqueue *kq = NULL;
+       int policy;
+       void *hook = NULL;
+       uint64_t kq_addr_offset;
 
-       assert(callback != NULL);
+       if (flags & KEVENT_FLAG_WORKQ) {
+               struct kqworkq *kqwq;
+               int i;
 
-       first = 1;
-       for (;;) {
-               wait_result_t wait_result;
-               int count;
+               kqwq = (struct kqworkq *)zalloc(kqworkq_zone);
+               if (kqwq == NULL)
+                       return NULL;
 
-               /*
-                * Make a pass through the kq to find events already
-                * triggered.  
-                */
-               kqlock(kq);
-               error = kqueue_process(kq, callback, data, &count, p);
-               if (error || count)
-                       break; /* lock still held */
+               kq = &kqwq->kqwq_kqueue;
+               bzero(kqwq, sizeof (struct kqworkq));
 
-               /* looks like we have to consider blocking */
-               if (first) {
-                       first = 0;
-                       /* convert the timeout to a deadline once */
-                       if (atvp->tv_sec || atvp->tv_usec) {
-                               uint64_t now;
-                               
-                               clock_get_uptime(&now);
-                               nanoseconds_to_absolutetime((uint64_t)atvp->tv_sec * NSEC_PER_SEC +
-                                                           atvp->tv_usec * NSEC_PER_USEC,
-                                                           &deadline);
-                               if (now >= deadline) {
-                                       /* non-blocking call */
-                                       error = EWOULDBLOCK;
-                                       break; /* lock still held */
-                               }
-                               deadline -= now;
-                               clock_absolutetime_interval_to_deadline(deadline, &deadline);
-                       } else {
-                               deadline = 0;   /* block forever */
-                       }
+               kqwq->kqwq_state = KQ_WORKQ;
 
-                       if (continuation) {
-                               uthread_t ut = (uthread_t)get_bsdthread_info(current_thread());
+               for (i = 0; i < KQWQ_NBUCKETS; i++) {
+                       TAILQ_INIT(&kq->kq_queue[i]);
+               }
+               for (i = 0; i < KQWQ_NQOS; i++) {
+                       kqwq->kqwq_request[i].kqr_qos_index = i;
+               }
+
+               lck_spin_init(&kqwq->kqwq_reqlock, kq_lck_grp, kq_lck_attr);
+               policy = SYNC_POLICY_FIFO;
+               hook = (void *)kqwq;
+               
+       } else if (flags & KEVENT_FLAG_WORKLOOP) {
+               struct kqworkloop *kqwl;
+               int i;
+
+               kqwl = (struct kqworkloop *)zalloc(kqworkloop_zone);
+               if (kqwl == NULL)
+                       return NULL;
+
+               bzero(kqwl, sizeof (struct kqworkloop));
+
+               kqwl->kqwl_state = KQ_WORKLOOP | KQ_DYNAMIC;
+               kqwl->kqwl_retains = 1; /* donate a retain to creator */
+
+               kq = &kqwl->kqwl_kqueue;
+               for (i = 0; i < KQWL_NBUCKETS; i++) {
+                       TAILQ_INIT(&kq->kq_queue[i]);
+               }
+               TAILQ_INIT(&kqwl->kqwl_request.kqr_suppressed);
+
+               lck_spin_init(&kqwl->kqwl_reqlock, kq_lck_grp, kq_lck_attr);
+               lck_mtx_init(&kqwl->kqwl_statelock, kq_lck_grp, kq_lck_attr);
+
+               policy = SYNC_POLICY_FIFO;
+               if (flags & KEVENT_FLAG_WORKLOOP_NO_WQ_THREAD) {
+                       policy |= SYNC_POLICY_PREPOST;
+                       kq->kq_state |= KQ_NO_WQ_THREAD;
+               } else {
+                       hook = (void *)kqwl;
+               }
+               
+       } else {
+               struct kqfile *kqf;
+               
+               kqf = (struct kqfile *)zalloc(kqfile_zone);
+               if (kqf == NULL)
+                       return NULL;
+
+               kq = &kqf->kqf_kqueue;
+               bzero(kqf, sizeof (struct kqfile));
+               TAILQ_INIT(&kq->kq_queue[0]);
+               TAILQ_INIT(&kqf->kqf_suppressed);
+               
+               policy = SYNC_POLICY_FIFO | SYNC_POLICY_PREPOST;
+       }
+
+       waitq_set_init(&kq->kq_wqs, policy, NULL, hook);
+       lck_spin_init(&kq->kq_lock, kq_lck_grp, kq_lck_attr);
+       kq->kq_p = p;
+
+       if (fdp->fd_knlistsize < 0) {
+               proc_fdlock(p);
+               if (fdp->fd_knlistsize < 0)
+                       fdp->fd_knlistsize = 0; /* this process has had a kq */
+               proc_fdunlock(p);
+       }
+
+       kq_addr_offset = ((uintptr_t)kq - (uintptr_t)VM_MIN_KERNEL_AND_KEXT_ADDRESS);
+       /* Assert that the address can be pointer compacted for use with knote */
+       assert(kq_addr_offset < (uint64_t)(1ull << KNOTE_KQ_BITSIZE));
+       return (kq);
+}
+
+/*
+ * knotes_dealloc - detach all knotes for the process and drop them
+ *
+ *             Called with proc_fdlock held.
+ *             Returns with it locked.
+ *             May drop it temporarily.
+ *             Process is in such a state that it will not try to allocate
+ *             any more knotes during this process (stopped for exit or exec).
+ */
+void
+knotes_dealloc(proc_t p)
+{
+       struct filedesc *fdp = p->p_fd;
+       struct kqueue *kq;
+       struct knote *kn;
+       struct  klist *kn_hash = NULL;
+       int i;
+
+       /* Close all the fd-indexed knotes up front */
+       if (fdp->fd_knlistsize > 0) {
+               for (i = 0; i < fdp->fd_knlistsize; i++) {
+                       while ((kn = SLIST_FIRST(&fdp->fd_knlist[i])) != NULL) {
+                               kq = knote_get_kq(kn);
+                               kqlock(kq);
+                               proc_fdunlock(p);
+                               /* drop it ourselves or wait */
+                               if (kqlock2knotedrop(kq, kn)) {
+                                       knote_drop(kn, p);
+                               }
+                               proc_fdlock(p);
+                       }
+               }
+               /* free the table */
+               FREE(fdp->fd_knlist, M_KQUEUE);
+               fdp->fd_knlist = NULL;
+       }
+       fdp->fd_knlistsize = -1;
+
+       knhash_lock(p);
+       proc_fdunlock(p);
+
+       /* Clean out all the hashed knotes as well */
+       if (fdp->fd_knhashmask != 0) {
+               for (i = 0; i <= (int)fdp->fd_knhashmask; i++) {
+                       while ((kn = SLIST_FIRST(&fdp->fd_knhash[i])) != NULL) {
+                               kq = knote_get_kq(kn);
+                               kqlock(kq);
+                               knhash_unlock(p);
+                               /* drop it ourselves or wait */
+                               if (kqlock2knotedrop(kq, kn)) {
+                                       knote_drop(kn, p);
+                               }
+                               knhash_lock(p);
+                       }
+               }
+               kn_hash = fdp->fd_knhash;
+               fdp->fd_knhashmask = 0;
+               fdp->fd_knhash = NULL;
+       }
+
+       knhash_unlock(p);
+
+       /* free the kn_hash table */
+       if (kn_hash)
+               FREE(kn_hash, M_KQUEUE);
+
+       proc_fdlock(p);
+}
+
+
+/*
+ * kqueue_dealloc - detach all knotes from a kqueue and free it
+ *
+ *     We walk each list looking for knotes referencing this
+ *     this kqueue.  If we find one, we try to drop it.  But
+ *     if we fail to get a drop reference, that will wait
+ *     until it is dropped.  So, we can just restart again
+ *     safe in the assumption that the list will eventually
+ *     not contain any more references to this kqueue (either
+ *     we dropped them all, or someone else did).
+ *
+ *     Assumes no new events are being added to the kqueue.
+ *     Nothing locked on entry or exit.
+ *
+ * Workloop kqueues cant get here unless all the knotes
+ * are already gone and all requested threads have come
+ * and gone (cancelled or arrived).
+ */
+void
+kqueue_dealloc(struct kqueue *kq)
+{
+       struct proc *p;
+       struct filedesc *fdp;
+       struct knote *kn;
+       int i;
+
+       if (kq == NULL)
+               return;
+
+       p = kq->kq_p;
+       fdp = p->p_fd;
+
+       proc_fdlock(p);
+       for (i = 0; i < fdp->fd_knlistsize; i++) {
+               kn = SLIST_FIRST(&fdp->fd_knlist[i]);
+               while (kn != NULL) {
+                       if (kq == knote_get_kq(kn)) {
+                               assert((kq->kq_state & KQ_WORKLOOP) == 0);
+                               kqlock(kq);
+                               proc_fdunlock(p);
+                               /* drop it ourselves or wait */
+                               if (kqlock2knotedrop(kq, kn)) {
+                                       knote_drop(kn, p);
+                               }
+                               proc_fdlock(p);
+                               /* start over at beginning of list */
+                               kn = SLIST_FIRST(&fdp->fd_knlist[i]);
+                               continue;
+                       }
+                       kn = SLIST_NEXT(kn, kn_link);
+               }
+       }
+       knhash_lock(p);
+       proc_fdunlock(p);
+
+       if (fdp->fd_knhashmask != 0) {
+               for (i = 0; i < (int)fdp->fd_knhashmask + 1; i++) {
+                       kn = SLIST_FIRST(&fdp->fd_knhash[i]);
+                       while (kn != NULL) {
+                               if (kq == knote_get_kq(kn)) {
+                                       assert((kq->kq_state & KQ_WORKLOOP) == 0);
+                                       kqlock(kq);
+                                       knhash_unlock(p);
+                                       /* drop it ourselves or wait */
+                                       if (kqlock2knotedrop(kq, kn)) {
+                                               knote_drop(kn, p);
+                                       }
+                                       knhash_lock(p);
+                                       /* start over at beginning of list */
+                                       kn = SLIST_FIRST(&fdp->fd_knhash[i]);
+                                       continue;
+                               }
+                               kn = SLIST_NEXT(kn, kn_link);
+                       }
+               }
+       }
+       knhash_unlock(p);
+
+       if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+               struct kqrequest *kqr = &kqwl->kqwl_request;
+               thread_t cur_owner = kqwl->kqwl_owner;
+
+               assert(TAILQ_EMPTY(&kqwl->kqwl_request.kqr_suppressed));
+               if (filt_wlowner_is_valid(cur_owner)) {
+                       /*
+                        * If the kqueue had an owner that prevented the thread request to
+                        * go through, then no unbind happened, and we may have lingering
+                        * overrides to drop.
+                        */
+                       if (kqr->kqr_dsync_owner_qos != THREAD_QOS_UNSPECIFIED) {
+                               thread_drop_ipc_override(cur_owner);
+                               kqr->kqr_dsync_owner_qos = THREAD_QOS_UNSPECIFIED;
+                       }
+
+                       if (kqr->kqr_owner_override_is_sync) {
+                               thread_drop_sync_ipc_override(cur_owner);
+                               kqr->kqr_owner_override_is_sync = 0;
+                       }
+                       thread_ends_owning_workloop(cur_owner);
+                       thread_deallocate(cur_owner);
+                       kqwl->kqwl_owner = THREAD_NULL;
+               }
+       }
+
+       /*
+        * waitq_set_deinit() remove the KQ's waitq set from
+        * any select sets to which it may belong.
+        */
+       waitq_set_deinit(&kq->kq_wqs);
+       lck_spin_destroy(&kq->kq_lock, kq_lck_grp);
+
+       if (kq->kq_state & KQ_WORKQ) {
+               struct kqworkq *kqwq = (struct kqworkq *)kq;
+
+               lck_spin_destroy(&kqwq->kqwq_reqlock, kq_lck_grp);
+               zfree(kqworkq_zone, kqwq);
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               assert(kqwl->kqwl_retains == 0);
+               lck_spin_destroy(&kqwl->kqwl_reqlock, kq_lck_grp);
+               lck_mtx_destroy(&kqwl->kqwl_statelock, kq_lck_grp);
+               zfree(kqworkloop_zone, kqwl);
+       } else {
+               struct kqfile *kqf = (struct kqfile *)kq;
+
+               zfree(kqfile_zone, kqf);
+       }
+}
+
+static inline void
+kqueue_retain(struct kqueue *kq)
+{
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       uint32_t previous;
+
+       if ((kq->kq_state & KQ_DYNAMIC) == 0)
+               return;
+
+       previous = OSIncrementAtomic(&kqwl->kqwl_retains);
+       if (previous == KQ_WORKLOOP_RETAINS_MAX)
+               panic("kq(%p) retain overflow", kq);
+
+       if (previous == 0)
+               panic("kq(%p) resurrection", kq);
+}
+
+#define KQUEUE_CANT_BE_LAST_REF  0
+#define KQUEUE_MIGHT_BE_LAST_REF 1
+
+static inline int
+kqueue_release(struct kqueue *kq, __assert_only int possibly_last)
+{
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+       if ((kq->kq_state & KQ_DYNAMIC) == 0) {
+               return 0;
+       }
+
+       assert(kq->kq_state & KQ_WORKLOOP); /* for now */
+       uint32_t refs = OSDecrementAtomic(&kqwl->kqwl_retains);
+       if (__improbable(refs == 0)) {
+               panic("kq(%p) over-release", kq);
+       }
+       if (refs == 1) {
+               assert(possibly_last);
+       }
+       return refs == 1;
+}
+
+int
+kqueue_body(struct proc *p, fp_allocfn_t fp_zalloc, void *cra, int32_t *retval)
+{
+       struct kqueue *kq;
+       struct fileproc *fp;
+       int fd, error;
+
+       error = falloc_withalloc(p,
+           &fp, &fd, vfs_context_current(), fp_zalloc, cra);
+       if (error) {
+               return (error);
+       }
+
+       kq = kqueue_alloc(p, 0);
+       if (kq == NULL) {
+               fp_free(p, fd, fp);
+               return (ENOMEM);
+       }
+
+       fp->f_flag = FREAD | FWRITE;
+       fp->f_ops = &kqueueops;
+       fp->f_data = kq;
+
+       proc_fdlock(p);
+       *fdflags(p, fd) |= UF_EXCLOSE;
+       procfdtbl_releasefd(p, fd, NULL);
+       fp_drop(p, fd, fp, 1);
+       proc_fdunlock(p);
+
+       *retval = fd;
+       return (error);
+}
+
+int
+kqueue(struct proc *p, __unused struct kqueue_args *uap, int32_t *retval)
+{
+       return (kqueue_body(p, fileproc_alloc_init, NULL, retval));
+}
+
+static int
+kevent_copyin(user_addr_t *addrp, struct kevent_internal_s *kevp, struct proc *p,
+    unsigned int flags)
+{
+       int advance;
+       int error;
+
+       if (flags & KEVENT_FLAG_LEGACY32) {
+               bzero(kevp, sizeof (*kevp));
+
+               if (IS_64BIT_PROCESS(p)) {
+                       struct user64_kevent kev64;
+
+                       advance = sizeof (kev64);
+                       error = copyin(*addrp, (caddr_t)&kev64, advance);
+                       if (error)
+                               return (error);
+                       kevp->ident = kev64.ident;
+                       kevp->filter = kev64.filter;
+                       kevp->flags = kev64.flags;
+                       kevp->udata = kev64.udata;
+                       kevp->fflags = kev64.fflags;
+                       kevp->data = kev64.data;
+               } else {
+                       struct user32_kevent kev32;
+
+                       advance = sizeof (kev32);
+                       error = copyin(*addrp, (caddr_t)&kev32, advance);
+                       if (error)
+                               return (error);
+                       kevp->ident = (uintptr_t)kev32.ident;
+                       kevp->filter = kev32.filter;
+                       kevp->flags = kev32.flags;
+                       kevp->udata = CAST_USER_ADDR_T(kev32.udata);
+                       kevp->fflags = kev32.fflags;
+                       kevp->data = (intptr_t)kev32.data;
+               }
+       } else if (flags & KEVENT_FLAG_LEGACY64) {
+               struct kevent64_s kev64;
+
+               bzero(kevp, sizeof (*kevp));
+
+               advance = sizeof (struct kevent64_s);
+               error = copyin(*addrp, (caddr_t)&kev64, advance);
+               if (error)
+                       return(error);
+               kevp->ident = kev64.ident;
+               kevp->filter = kev64.filter;
+               kevp->flags = kev64.flags;
+               kevp->udata = kev64.udata;
+               kevp->fflags = kev64.fflags;
+               kevp->data = kev64.data;
+               kevp->ext[0] = kev64.ext[0];
+               kevp->ext[1] = kev64.ext[1];
+               
+       } else {
+               struct kevent_qos_s kevqos;
+
+               bzero(kevp, sizeof (*kevp));
+
+               advance = sizeof (struct kevent_qos_s);
+               error = copyin(*addrp, (caddr_t)&kevqos, advance);
+               if (error)
+                       return error;
+               kevp->ident = kevqos.ident;
+               kevp->filter = kevqos.filter;
+               kevp->flags = kevqos.flags;
+               kevp->qos = kevqos.qos;
+//             kevp->xflags = kevqos.xflags;
+               kevp->udata = kevqos.udata;
+               kevp->fflags = kevqos.fflags;
+               kevp->data = kevqos.data;
+               kevp->ext[0] = kevqos.ext[0];
+               kevp->ext[1] = kevqos.ext[1];
+               kevp->ext[2] = kevqos.ext[2];
+               kevp->ext[3] = kevqos.ext[3];
+       }
+       if (!error)
+               *addrp += advance;
+       return (error);
+}
+
+static int
+kevent_copyout(struct kevent_internal_s *kevp, user_addr_t *addrp, struct proc *p,
+    unsigned int flags)
+{
+       user_addr_t addr = *addrp;
+       int advance;
+       int error;
+
+       /* 
+        * fully initialize the differnt output event structure
+        * types from the internal kevent (and some universal
+        * defaults for fields not represented in the internal
+        * form).
+        */
+       if (flags & KEVENT_FLAG_LEGACY32) {
+               assert((flags & KEVENT_FLAG_STACK_EVENTS) == 0);
+
+               if (IS_64BIT_PROCESS(p)) {
+                       struct user64_kevent kev64;
+
+                       advance = sizeof (kev64);
+                       bzero(&kev64, advance);
+                       
+                       /*
+                        * deal with the special case of a user-supplied
+                        * value of (uintptr_t)-1.
+                        */
+                       kev64.ident = (kevp->ident == (uintptr_t)-1) ?
+                               (uint64_t)-1LL : (uint64_t)kevp->ident;
+
+                       kev64.filter = kevp->filter;
+                       kev64.flags = kevp->flags;
+                       kev64.fflags = kevp->fflags;
+                       kev64.data = (int64_t) kevp->data;
+                       kev64.udata = kevp->udata;
+                       error = copyout((caddr_t)&kev64, addr, advance);
+               } else {
+                       struct user32_kevent kev32;
+
+                       advance = sizeof (kev32);
+                       bzero(&kev32, advance);
+                       kev32.ident = (uint32_t)kevp->ident;
+                       kev32.filter = kevp->filter;
+                       kev32.flags = kevp->flags;
+                       kev32.fflags = kevp->fflags;
+                       kev32.data = (int32_t)kevp->data;
+                       kev32.udata = kevp->udata;
+                       error = copyout((caddr_t)&kev32, addr, advance);
+               }
+       } else if (flags & KEVENT_FLAG_LEGACY64) {
+               struct kevent64_s kev64;
+
+               advance = sizeof (struct kevent64_s);
+               if (flags & KEVENT_FLAG_STACK_EVENTS) {
+                       addr -= advance;
+               }
+               bzero(&kev64, advance);
+               kev64.ident = kevp->ident;
+               kev64.filter = kevp->filter;
+               kev64.flags = kevp->flags;
+               kev64.fflags = kevp->fflags;
+               kev64.data = (int64_t) kevp->data;
+               kev64.udata = kevp->udata;
+               kev64.ext[0] = kevp->ext[0];
+               kev64.ext[1] = kevp->ext[1];
+               error = copyout((caddr_t)&kev64, addr, advance);
+       } else {
+               struct kevent_qos_s kevqos;
+          
+               advance = sizeof (struct kevent_qos_s);
+               if (flags & KEVENT_FLAG_STACK_EVENTS) {
+                       addr -= advance;
+               }
+               bzero(&kevqos, advance);
+               kevqos.ident = kevp->ident;
+               kevqos.filter = kevp->filter;
+               kevqos.flags = kevp->flags;
+               kevqos.qos = kevp->qos;
+               kevqos.udata = kevp->udata;
+               kevqos.fflags = kevp->fflags;
+               kevqos.xflags = 0;
+               kevqos.data = (int64_t) kevp->data;
+               kevqos.ext[0] = kevp->ext[0];
+               kevqos.ext[1] = kevp->ext[1];
+               kevqos.ext[2] = kevp->ext[2];
+               kevqos.ext[3] = kevp->ext[3];
+               error = copyout((caddr_t)&kevqos, addr, advance);
+       }
+       if (!error) {
+               if (flags & KEVENT_FLAG_STACK_EVENTS)
+                       *addrp = addr;
+               else
+                       *addrp = addr + advance;
+       }
+       return (error);
+}
+
+static int
+kevent_get_data_size(struct proc *p, 
+                     uint64_t data_available,
+                     unsigned int flags,
+                     user_size_t *residp)
+{
+       user_size_t resid;
+       int error = 0;
+
+       if (data_available != USER_ADDR_NULL) {
+               if (flags & KEVENT_FLAG_KERNEL) {
+                       resid = *(user_size_t *)(uintptr_t)data_available;
+               } else if (IS_64BIT_PROCESS(p)) {
+                       user64_size_t usize;
+                       error = copyin((user_addr_t)data_available, &usize, sizeof(usize));
+                       resid = (user_size_t)usize;
+               } else {
+                       user32_size_t usize;
+                       error = copyin((user_addr_t)data_available, &usize, sizeof(usize));
+                       resid = (user_size_t)usize;
+               }
+               if (error)
+                       return(error);
+       } else {
+               resid = 0;
+       }
+       *residp = resid;
+       return 0;
+}
+
+static int
+kevent_put_data_size(struct proc *p, 
+                     uint64_t data_available,
+                     unsigned int flags,
+                     user_size_t resid)
+{
+       int error = 0;
+
+       if (data_available) {
+               if (flags & KEVENT_FLAG_KERNEL) {
+                       *(user_size_t *)(uintptr_t)data_available = resid;
+               } else if (IS_64BIT_PROCESS(p)) {
+                       user64_size_t usize = (user64_size_t)resid;
+                       error = copyout(&usize, (user_addr_t)data_available, sizeof(usize));
+               } else {
+                       user32_size_t usize = (user32_size_t)resid;
+                       error = copyout(&usize, (user_addr_t)data_available, sizeof(usize));
+               }
+       }
+       return error;
+}
+
+/*
+ * kevent_continue - continue a kevent syscall after blocking
+ *
+ *     assume we inherit a use count on the kq fileglob.
+ */
+
+__attribute__((noreturn))
+static void
+kevent_continue(__unused struct kqueue *kq, void *data, int error)
+{
+       struct _kevent *cont_args;
+       struct fileproc *fp;
+       uint64_t data_available;
+       user_size_t data_size;
+       user_size_t data_resid;
+       unsigned int flags;
+       int32_t *retval;
+       int noutputs;
+       int fd;
+       struct proc *p = current_proc();
+
+       cont_args = (struct _kevent *)data;
+       data_available = cont_args->data_available;
+       flags = cont_args->process_data.fp_flags;
+       data_size = cont_args->process_data.fp_data_size;
+       data_resid = cont_args->process_data.fp_data_resid;
+       noutputs = cont_args->eventout;
+       retval = cont_args->retval;
+       fd = cont_args->fd;
+       fp = cont_args->fp;
+
+       kevent_put_kq(p, fd, fp, kq);
+
+       /* don't abandon other output just because of residual copyout failures */
+       if (error == 0 && data_available && data_resid != data_size) {
+               (void)kevent_put_data_size(p, data_available, flags, data_resid);
+       }
+
+       /* don't restart after signals... */
+       if (error == ERESTART)
+               error = EINTR;
+       else if (error == EWOULDBLOCK)
+               error = 0;
+       if (error == 0)
+               *retval = noutputs;
+       unix_syscall_return(error);
+}
+
+/*
+ * kevent - [syscall] register and wait for kernel events
+ *
+ */
+int
+kevent(struct proc *p, struct kevent_args *uap, int32_t *retval)
+{
+       unsigned int flags = KEVENT_FLAG_LEGACY32;
+
+       return kevent_internal(p,
+                              (kqueue_id_t)uap->fd, NULL,
+                              uap->changelist, uap->nchanges,
+                              uap->eventlist, uap->nevents,
+                              0ULL, 0ULL,
+                              flags,
+                              uap->timeout,
+                              kevent_continue,
+                              retval);
+}
+
+int
+kevent64(struct proc *p, struct kevent64_args *uap, int32_t *retval)
+{
+       unsigned int flags;
+
+       /* restrict to user flags and set legacy64 */
+       flags = uap->flags & KEVENT_FLAG_USER;
+       flags |= KEVENT_FLAG_LEGACY64;
+
+       return kevent_internal(p,
+                              (kqueue_id_t)uap->fd, NULL,
+                              uap->changelist, uap->nchanges,
+                              uap->eventlist, uap->nevents,
+                              0ULL, 0ULL,
+                              flags,
+                              uap->timeout,
+                              kevent_continue,
+                              retval);
+}
+
+int
+kevent_qos(struct proc *p, struct kevent_qos_args *uap, int32_t *retval)
+{
+       /* restrict to user flags */
+       uap->flags &= KEVENT_FLAG_USER;
+
+       return kevent_internal(p,
+                              (kqueue_id_t)uap->fd, NULL,
+                              uap->changelist, uap->nchanges,
+                              uap->eventlist,  uap->nevents,
+                              uap->data_out, (uint64_t)uap->data_available,
+                              uap->flags,
+                              0ULL,
+                              kevent_continue,
+                              retval);
+}
+
+int 
+kevent_qos_internal(struct proc *p, int fd, 
+                   user_addr_t changelist, int nchanges,
+                   user_addr_t eventlist, int nevents,
+                   user_addr_t data_out, user_size_t *data_available,
+                   unsigned int flags, 
+                   int32_t *retval) 
+{
+       return kevent_internal(p,
+                              (kqueue_id_t)fd, NULL,
+                              changelist, nchanges,
+                              eventlist, nevents,
+                              data_out, (uint64_t)data_available,
+                              (flags | KEVENT_FLAG_KERNEL),
+                              0ULL,
+                              NULL,
+                              retval);
+}
+
+int
+kevent_id(struct proc *p, struct kevent_id_args *uap, int32_t *retval)
+{
+       /* restrict to user flags */
+       uap->flags &= KEVENT_FLAG_USER;
+
+       return kevent_internal(p,
+                              (kqueue_id_t)uap->id, NULL,
+                              uap->changelist, uap->nchanges,
+                              uap->eventlist,  uap->nevents,
+                              uap->data_out, (uint64_t)uap->data_available,
+                              (uap->flags | KEVENT_FLAG_DYNAMIC_KQUEUE),
+                              0ULL,
+                              kevent_continue,
+                              retval);
+}
+
+int
+kevent_id_internal(struct proc *p, kqueue_id_t *id,
+                   user_addr_t changelist, int nchanges,
+                   user_addr_t eventlist, int nevents,
+                   user_addr_t data_out, user_size_t *data_available,
+                   unsigned int flags, 
+                   int32_t *retval) 
+{
+       return kevent_internal(p,
+                              *id, id,
+                              changelist, nchanges,
+                              eventlist, nevents,
+                              data_out, (uint64_t)data_available,
+                              (flags | KEVENT_FLAG_KERNEL | KEVENT_FLAG_DYNAMIC_KQUEUE),
+                              0ULL,
+                              NULL,
+                              retval);
+}
+static int
+kevent_get_timeout(struct proc *p,
+                  user_addr_t utimeout,
+                  unsigned int flags,
+                  struct timeval *atvp)
+{
+       struct timeval atv;
+       int error = 0;
+
+       if (flags & KEVENT_FLAG_IMMEDIATE) {
+               getmicrouptime(&atv);
+       } else if (utimeout != USER_ADDR_NULL) {
+               struct timeval rtv;
+               if (flags & KEVENT_FLAG_KERNEL) {
+                       struct timespec *tsp = (struct timespec *)utimeout;
+                       TIMESPEC_TO_TIMEVAL(&rtv, tsp);
+               } else if (IS_64BIT_PROCESS(p)) {
+                       struct user64_timespec ts;
+                       error = copyin(utimeout, &ts, sizeof(ts));
+                       if ((ts.tv_sec & 0xFFFFFFFF00000000ull) != 0)
+                               error = EINVAL;
+                       else
+                               TIMESPEC_TO_TIMEVAL(&rtv, &ts);
+               } else {
+                       struct user32_timespec ts;
+                       error = copyin(utimeout, &ts, sizeof(ts));
+                       TIMESPEC_TO_TIMEVAL(&rtv, &ts);
+               }
+               if (error)
+                       return (error);
+               if (itimerfix(&rtv))
+                       return (EINVAL);
+               getmicrouptime(&atv);
+               timevaladd(&atv, &rtv);
+       } else {
+               /* wait forever value */
+               atv.tv_sec = 0;
+               atv.tv_usec = 0;
+       }
+       *atvp = atv;
+       return 0;
+}
+
+static int
+kevent_set_kq_mode(struct kqueue *kq, unsigned int flags)
+{
+       /* each kq should only be used for events of one type */
+       kqlock(kq);
+       if (kq->kq_state & (KQ_KEV32 | KQ_KEV64 | KQ_KEV_QOS)) {
+               if (flags & KEVENT_FLAG_LEGACY32) {
+                       if ((kq->kq_state & KQ_KEV32) == 0) {
+                               kqunlock(kq);
+                               return EINVAL;
+                       }
+               } else if (kq->kq_state & KQ_KEV32) {
+                       kqunlock(kq);
+                       return EINVAL;
+               }
+       } else if (flags & KEVENT_FLAG_LEGACY32) {
+               kq->kq_state |= KQ_KEV32;
+       } else if (flags & KEVENT_FLAG_LEGACY64) {
+               kq->kq_state |= KQ_KEV64;
+       } else {
+               kq->kq_state |= KQ_KEV_QOS;
+       }
+       kqunlock(kq);
+       return 0;
+}
+
+#define        KQ_HASH(val, mask)  (((val) ^ (val >> 8)) & (mask))
+#define CONFIG_KQ_HASHSIZE  CONFIG_KN_HASHSIZE
+
+static inline void
+kqhash_lock(proc_t p)
+{
+       lck_mtx_lock_spin_always(&p->p_fd->fd_kqhashlock);
+}
+
+static inline void
+kqhash_lock_held(__assert_only proc_t p)
+{
+       LCK_MTX_ASSERT(&p->p_fd->fd_kqhashlock, LCK_MTX_ASSERT_OWNED);
+}
+
+static inline void
+kqhash_unlock(proc_t p)
+{
+       lck_mtx_unlock(&p->p_fd->fd_kqhashlock);
+}
+
+static void
+kqueue_hash_init_if_needed(proc_t p)
+{
+       struct filedesc *fdp = p->p_fd;
+
+       kqhash_lock_held(p);
+
+       if (__improbable(fdp->fd_kqhash == NULL)) {
+               struct kqlist *alloc_hash;
+               u_long alloc_mask;
+
+               kqhash_unlock(p);
+               alloc_hash = hashinit(CONFIG_KQ_HASHSIZE, M_KQUEUE, &alloc_mask);
+               kqhash_lock(p);
+
+               /* See if we won the race */
+               if (fdp->fd_kqhashmask == 0) {
+                       fdp->fd_kqhash = alloc_hash;
+                       fdp->fd_kqhashmask = alloc_mask;
+               } else {
+                       kqhash_unlock(p);
+                       FREE(alloc_hash, M_KQUEUE);
+                       kqhash_lock(p);
+               }
+       }
+}
+
+/*
+ * Called with the kqhash_lock() held
+ */
+static void
+kqueue_hash_insert(
+       struct proc *p,
+       kqueue_id_t id,
+       struct kqueue *kq)
+{
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       struct filedesc *fdp = p->p_fd;
+       struct kqlist *list;
+
+       /* should hold the kq hash lock */
+       kqhash_lock_held(p);
+
+       if ((kq->kq_state & KQ_DYNAMIC) == 0) {
+               assert(kq->kq_state & KQ_DYNAMIC);
+               return;
+       }
+
+       /* only dynamically allocate workloop kqs for now */
+       assert(kq->kq_state & KQ_WORKLOOP);
+       assert(fdp->fd_kqhash);
+
+       kqwl->kqwl_dynamicid = id;
+
+       list = &fdp->fd_kqhash[KQ_HASH(id, fdp->fd_kqhashmask)];
+       SLIST_INSERT_HEAD(list, kqwl, kqwl_hashlink);
+}
+
+/* Called with kqhash_lock held */
+static void
+kqueue_hash_remove(
+       struct proc *p,
+       struct kqueue *kq)
+{
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       struct filedesc *fdp = p->p_fd;
+       struct kqlist *list;
+
+       /* should hold the kq hash lock */
+       kqhash_lock_held(p);
+
+       if ((kq->kq_state & KQ_DYNAMIC) == 0) {
+               assert(kq->kq_state & KQ_DYNAMIC);
+               return;
+       }
+       assert(kq->kq_state & KQ_WORKLOOP); /* for now */
+       list = &fdp->fd_kqhash[KQ_HASH(kqwl->kqwl_dynamicid, fdp->fd_kqhashmask)];
+       SLIST_REMOVE(list, kqwl, kqworkloop, kqwl_hashlink);
+}
+
+/* Called with kqhash_lock held */
+static struct kqueue *
+kqueue_hash_lookup(struct proc *p, kqueue_id_t id)
+{
+       struct filedesc *fdp = p->p_fd;
+       struct kqlist *list;
+       struct kqworkloop *kqwl;
+
+       /* should hold the kq hash lock */
+       kqhash_lock_held(p);
+
+       if (fdp->fd_kqhashmask == 0) return NULL;
+
+       list = &fdp->fd_kqhash[KQ_HASH(id, fdp->fd_kqhashmask)];
+       SLIST_FOREACH(kqwl, list, kqwl_hashlink) {
+               if (kqwl->kqwl_dynamicid == id) {
+                       struct kqueue *kq = (struct kqueue *)kqwl;
+
+                       assert(kq->kq_state & KQ_DYNAMIC);
+                       assert(kq->kq_state & KQ_WORKLOOP); /* for now */
+                       return kq;
+               }
+       }
+       return NULL;
+}
+
+static inline void
+kqueue_release_last(struct proc *p, struct kqueue *kq)
+{
+       if (kq->kq_state & KQ_DYNAMIC) {
+               kqhash_lock(p);
+               if (kqueue_release(kq, KQUEUE_MIGHT_BE_LAST_REF)) {
+                       kqueue_hash_remove(p, kq);
+                       kqhash_unlock(p);
+                       kqueue_dealloc(kq);
+               } else {
+                       kqhash_unlock(p);
+               }
+       }
+}
+
+static struct kqueue *
+kevent_get_bound_kq(__assert_only struct proc *p, thread_t thread,
+                    unsigned int kev_flags, unsigned int kq_flags)
+{
+       struct kqueue *kq;
+       struct uthread *ut = get_bsdthread_info(thread);
+
+       assert(p == get_bsdthreadtask_info(thread));
+
+       if (!(ut->uu_kqueue_flags & kev_flags))
+               return NULL;
+
+       kq = ut->uu_kqueue_bound;
+       if (!kq)
+               return NULL;
+
+       if (!(kq->kq_state & kq_flags))
+               return NULL;
+
+       return kq;
+}
+
+static int
+kevent_get_kq(struct proc *p, kqueue_id_t id, unsigned int flags, struct fileproc **fpp, int *fdp, struct kqueue **kqp)
+{
+       struct filedesc *descp = p->p_fd;
+       struct fileproc *fp = NULL;
+       struct kqueue *kq;
+       int fd = 0;
+       int error = 0;
+
+       /* Was the workloop flag passed?  Then it is for sure only a workloop */
+       if (flags & KEVENT_FLAG_DYNAMIC_KQUEUE) {
+               assert(flags & KEVENT_FLAG_WORKLOOP);
+               if (id == (kqueue_id_t)-1 &&
+                   (flags & KEVENT_FLAG_KERNEL) &&
+                   (flags & KEVENT_FLAG_WORKLOOP)) {
+
+                       assert(is_workqueue_thread(current_thread()));
+
+                       /*
+                        * when kevent_id_internal is called from within the
+                        * kernel, and the passed 'id' value is '-1' then we
+                        * look for the currently bound workloop kq.
+                        *
+                        * Until pthread kext avoids calling in to kevent_id_internal
+                        * for threads whose fulfill is canceled, calling in unbound
+                        * can't be fatal.
+                        */
+                       kq = kevent_get_bound_kq(p, current_thread(),
+                                                KEVENT_FLAG_WORKLOOP, KQ_WORKLOOP);
+                       if (kq) {
+                               kqueue_retain(kq);
+                       } else {
+                               struct uthread *ut = get_bsdthread_info(current_thread());
+
+                               /* If thread is unbound due to cancel, just return an error */
+                               if (ut->uu_kqueue_flags == KEVENT_FLAG_WORKLOOP_CANCELED) {
+                                       ut->uu_kqueue_flags = 0;
+                                       error = ECANCELED;
+                               } else {
+                                       panic("Unbound thread called kevent_internal with id=-1"
+                                             " uu_kqueue_flags:0x%x, uu_kqueue_bound:%p",
+                                             ut->uu_kqueue_flags, ut->uu_kqueue_bound);
+                               }
+                       }
+
+                       *fpp = NULL;
+                       *fdp = 0;
+                       *kqp = kq;
+                       return error;
+               }
+
+               /* try shortcut on kq lookup for bound threads */
+               kq = kevent_get_bound_kq(p, current_thread(), KEVENT_FLAG_WORKLOOP, KQ_WORKLOOP);
+               if (kq != NULL && ((struct kqworkloop *)kq)->kqwl_dynamicid == id) {
+
+                       if (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST) {
+                               error = EEXIST;
+                               kq = NULL;
+                               goto out;
+                       }
+
+                       /* retain a reference while working with this kq. */
+                       assert(kq->kq_state & KQ_DYNAMIC);
+                       kqueue_retain(kq);
+                       error = 0;
+                       goto out;
+               }
+
+               /* look for the kq on the hash table */
+               kqhash_lock(p);
+               kq = kqueue_hash_lookup(p, id);
+               if (kq == NULL) {
+                       kqhash_unlock(p);
+
+                       if (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST) {
+                               error = ENOENT;
+                               goto out;
+                       }
+
+                       struct kqueue *alloc_kq;
+                       alloc_kq = kqueue_alloc(p, flags);
+                       if (alloc_kq) {
+                               kqhash_lock(p);
+                               kqueue_hash_init_if_needed(p);
+                               kq = kqueue_hash_lookup(p, id);
+                               if (kq == NULL) {
+                                       /* insert our new one */
+                                       kq = alloc_kq;
+                                       kqueue_hash_insert(p, id, kq);
+                                       kqhash_unlock(p);
+                               } else {
+                                       /* lost race, retain existing workloop */
+                                       kqueue_retain(kq);
+                                       kqhash_unlock(p);
+                                       kqueue_release(alloc_kq, KQUEUE_MIGHT_BE_LAST_REF);
+                                       kqueue_dealloc(alloc_kq);
+                               }
+                       } else {
+                               error = ENOMEM;
+                               goto out;
+                       }
+               } else {
+
+                       if (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST) {
+                               kqhash_unlock(p);
+                               kq = NULL;
+                               error =  EEXIST;
+                               goto out;
+                       }
+
+                       /* retain a reference while working with this kq. */
+                       assert(kq->kq_state & KQ_DYNAMIC);
+                       kqueue_retain(kq);
+                       kqhash_unlock(p);
+               }
+               
+       } else if (flags & KEVENT_FLAG_WORKQ) {
+               /* must already exist for bound threads. */
+               if (flags & KEVENT_FLAG_KERNEL) {
+                       assert(descp->fd_wqkqueue != NULL);
+               }
+
+               /*
+                * use the private kq associated with the proc workq.
+                * Just being a thread within the process (and not
+                * being the exit/exec thread) is enough to hold a
+                * reference on this special kq.
+                */
+               kq = descp->fd_wqkqueue;
+               if (kq == NULL) {
+                       struct kqueue *alloc_kq = kqueue_alloc(p, KEVENT_FLAG_WORKQ);
+                       if (alloc_kq == NULL)
+                               return ENOMEM;
+
+                       knhash_lock(p);
+                       if (descp->fd_wqkqueue == NULL) {
+                               kq = descp->fd_wqkqueue = alloc_kq;
+                               knhash_unlock(p);
+                       } else {
+                               knhash_unlock(p);
+                               kq = descp->fd_wqkqueue;
+                               kqueue_dealloc(alloc_kq);
+                       }
+               }
+       } else {
+               /* get a usecount for the kq itself */
+               fd = (int)id;
+               if ((error = fp_getfkq(p, fd, &fp, &kq)) != 0)
+                       return (error);
+       }
+       if ((error = kevent_set_kq_mode(kq, flags)) != 0) {
+               /* drop the usecount */
+               if (fp != NULL)
+                       fp_drop(p, fd, fp, 0);
+               return error;
+       } 
+
+out:
+       *fpp = fp;
+       *fdp = fd;
+       *kqp = kq;
+       
+       return error;
+}
+
+static void
+kevent_put_kq(
+       struct proc *p,
+       kqueue_id_t id,
+       struct fileproc *fp,
+       struct kqueue *kq)
+{
+       kqueue_release_last(p, kq);
+       if (fp != NULL) {
+               assert((kq->kq_state & KQ_WORKQ) == 0);
+               fp_drop(p, (int)id, fp, 0);
+       }
+}
+
+static uint64_t
+kevent_workloop_serial_no_copyin(proc_t p, uint64_t workloop_id)
+{
+       uint64_t serial_no = 0;
+       user_addr_t addr;
+       int rc;
+
+       if (workloop_id == 0 || p->p_dispatchqueue_serialno_offset == 0) {
+               return 0;
+       }
+       addr = (user_addr_t)(workloop_id + p->p_dispatchqueue_serialno_offset);
+
+       if (proc_is64bit(p)) {
+               rc = copyin(addr, (caddr_t)&serial_no, sizeof(serial_no));
+       } else {
+               uint32_t serial_no32 = 0;
+               rc = copyin(addr, (caddr_t)&serial_no32, sizeof(serial_no32));
+               serial_no = serial_no32;
+       }
+       return rc == 0 ? serial_no : 0;
+}
+
+int
+kevent_exit_on_workloop_ownership_leak(thread_t thread)
+{
+       proc_t p = current_proc();
+       struct filedesc *fdp = p->p_fd;
+       kqueue_id_t workloop_id = 0;
+       os_reason_t reason;
+       mach_vm_address_t addr;
+       uint32_t reason_size;
+
+       kqhash_lock(p);
+       if (fdp->fd_kqhashmask > 0) {
+               for (uint32_t i = 0; i < fdp->fd_kqhashmask + 1; i++) {
+                       struct kqworkloop *kqwl;
+
+                       SLIST_FOREACH(kqwl, &fdp->fd_kqhash[i], kqwl_hashlink) {
+                               struct kqueue *kq = &kqwl->kqwl_kqueue;
+                               if ((kq->kq_state & KQ_DYNAMIC) && kqwl->kqwl_owner == thread) {
+                                       workloop_id = kqwl->kqwl_dynamicid;
+                                       break;
+                               }
+                       }
+               }
+       }
+       kqhash_unlock(p);
+       assert(workloop_id);
+
+       reason = os_reason_create(OS_REASON_LIBSYSTEM,
+                       OS_REASON_LIBSYSTEM_CODE_WORKLOOP_OWNERSHIP_LEAK);
+       if (reason == OS_REASON_NULL) {
+               goto out;
+       }
+
+       reason->osr_flags |= OS_REASON_FLAG_GENERATE_CRASH_REPORT;
+       reason_size = 2 * sizeof(uint64_t);
+       reason_size = kcdata_estimate_required_buffer_size(2, reason_size);
+       if (os_reason_alloc_buffer(reason, reason_size) != 0) {
+               goto out;
+       }
+
+       struct kcdata_descriptor *kcd = &reason->osr_kcd_descriptor;
+
+       if (kcdata_get_memory_addr(kcd, EXIT_REASON_WORKLOOP_ID,
+                       sizeof(workloop_id), &addr) == KERN_SUCCESS) {
+               kcdata_memcpy(kcd, addr, &workloop_id, sizeof(workloop_id));
+       }
+
+       uint64_t serial_no = kevent_workloop_serial_no_copyin(p, workloop_id);
+       if (serial_no && kcdata_get_memory_addr(kcd, EXIT_REASON_DISPATCH_QUEUE_NO,
+                       sizeof(serial_no), &addr) == KERN_SUCCESS) {
+               kcdata_memcpy(kcd, addr, &serial_no, sizeof(serial_no));
+       }
+
+out:
+#if DEVELOPMENT || DEBUG
+       psignal_try_thread_with_reason(p, thread, SIGABRT, reason);
+       return 0;
+#else
+       return exit_with_reason(p, W_EXITCODE(0, SIGKILL), (int *)NULL,
+                       FALSE, FALSE, 0, reason);
+#endif
+}
+
+
+static int
+kevent_servicer_detach_preflight(thread_t thread, unsigned int flags, struct kqueue *kq)
+{
+       int error = 0;
+       struct kqworkloop *kqwl;
+       struct uthread *ut;
+       struct kqrequest *kqr;
+
+       if (!(flags & KEVENT_FLAG_WORKLOOP) || !(kq->kq_state & KQ_WORKLOOP))
+               return EINVAL;
+
+       /* only kq created with KEVENT_FLAG_WORKLOOP_NO_WQ_THREAD from userspace can have attached threads */
+       if (!(kq->kq_state & KQ_NO_WQ_THREAD))
+               return EINVAL;
+
+       /* allow detach only on not wq threads */
+       if (is_workqueue_thread(thread))
+               return EINVAL;
+
+       /* check that the current thread is bound to the requested wq */
+       ut = get_bsdthread_info(thread);
+       if (ut->uu_kqueue_bound != kq)
+               return EINVAL;
+
+       kqwl = (struct kqworkloop *)kq;
+       kqwl_req_lock(kqwl);
+       kqr = &kqwl->kqwl_request;
+
+       /* check that the wq is bound to the thread */
+       if ((kqr->kqr_state & KQR_BOUND) == 0  || (kqr->kqr_thread != thread))
+               error = EINVAL;
+
+       kqwl_req_unlock(kqwl);
+
+       return error;
+}
+
+static void
+kevent_servicer_detach_thread(struct proc *p, kqueue_id_t id, thread_t thread,
+               unsigned int flags, struct kqueue *kq)
+{
+       struct kqworkloop *kqwl;
+       struct uthread *ut;
+
+       assert((flags & KEVENT_FLAG_WORKLOOP) && (kq->kq_state & KQ_WORKLOOP));
+
+       /* allow detach only on not wqthreads threads */
+       assert(!is_workqueue_thread(thread));
+
+       /* only kq created with KEVENT_FLAG_WORKLOOP_NO_WQ_THREAD from userspace can have attached threads */
+       assert(kq->kq_state & KQ_NO_WQ_THREAD);
+
+       /* check that the current thread is bound to the requested kq */
+       ut = get_bsdthread_info(thread);
+       assert(ut->uu_kqueue_bound == kq);
+
+       kqwl = (struct kqworkloop *)kq;
+
+       kqlock(kq);
+
+       /* unbind the thread.
+        * unbind itself checks if still processing and ends it.
+        */
+       kqworkloop_unbind_thread(kqwl, thread, flags);
+
+       kqunlock(kq);
+
+       kevent_put_kq(p, id, NULL, kq);
+
+       return;
+}
+
+static int
+kevent_servicer_attach_thread(thread_t thread, unsigned int flags, struct kqueue *kq)
+{
+       int error = 0;
+       struct kqworkloop *kqwl;
+       struct uthread *ut;
+       struct kqrequest *kqr;
+
+       if (!(flags & KEVENT_FLAG_WORKLOOP) || !(kq->kq_state & KQ_WORKLOOP))
+               return EINVAL;
+
+       /* only kq created with KEVENT_FLAG_WORKLOOP_NO_WQ_THREAD from userspace can have attached threads*/
+       if (!(kq->kq_state & KQ_NO_WQ_THREAD))
+               return EINVAL;
+
+       /* allow attach only on not wqthreads */
+       if (is_workqueue_thread(thread))
+               return EINVAL;
+
+       /* check that the thread is not already bound */
+       ut = get_bsdthread_info(thread);
+       if (ut->uu_kqueue_bound != NULL)
+               return EINVAL;
+
+       assert(ut->uu_kqueue_flags == 0);
+
+       kqlock(kq);
+       kqwl = (struct kqworkloop *)kq;
+       kqwl_req_lock(kqwl);
+       kqr = &kqwl->kqwl_request;
+
+       /* check that the kqueue is not already bound */
+       if (kqr->kqr_state & (KQR_BOUND | KQR_THREQUESTED | KQR_DRAIN)) {
+               error = EINVAL;
+               goto out;
+       }
+
+       assert(kqr->kqr_thread == NULL);
+       assert((kqr->kqr_state & KQR_PROCESSING) == 0);
+
+       kqr->kqr_state |= KQR_THREQUESTED;
+       kqr->kqr_qos_index = THREAD_QOS_UNSPECIFIED;
+       kqr->kqr_override_index = THREAD_QOS_UNSPECIFIED;
+       kqr->kqr_dsync_owner_qos = THREAD_QOS_UNSPECIFIED;
+       kqr->kqr_owner_override_is_sync = 0;
+
+       kqworkloop_bind_thread_impl(kqwl, thread, KEVENT_FLAG_WORKLOOP);
+
+       /* get a ref on the wlkq on behalf of the attached thread */
+       kqueue_retain(kq);
+
+out:
+       kqwl_req_unlock(kqwl);
+       kqunlock(kq);
+
+       return error;
+}
+
+static inline
+boolean_t kevent_args_requesting_events(unsigned int flags, int nevents)
+{
+       return (!(flags & KEVENT_FLAG_ERROR_EVENTS) && nevents > 0);
+}
+
+static int
+kevent_internal(struct proc *p,
+               kqueue_id_t id, kqueue_id_t *id_out,
+               user_addr_t changelist, int nchanges,
+               user_addr_t ueventlist, int nevents,
+               user_addr_t data_out, uint64_t data_available,
+               unsigned int flags, 
+               user_addr_t utimeout,
+               kqueue_continue_t continuation,
+               int32_t *retval)
+{
+       struct _kevent *cont_args;
+       uthread_t ut;
+       struct kqueue *kq;
+       struct fileproc *fp = NULL;
+       int fd = 0;
+       struct kevent_internal_s kev;
+       int error, noutputs;
+       struct timeval atv;
+       user_size_t data_size;
+       user_size_t data_resid;
+       thread_t thread = current_thread();
+
+       /* Don't allow user-space threads to process output events from the workq kqs */
+       if (((flags & (KEVENT_FLAG_WORKQ | KEVENT_FLAG_KERNEL)) == KEVENT_FLAG_WORKQ) &&
+           kevent_args_requesting_events(flags, nevents))
+               return EINVAL;
+
+       /* restrict dynamic kqueue allocation to workloops (for now) */
+       if ((flags & (KEVENT_FLAG_DYNAMIC_KQUEUE | KEVENT_FLAG_WORKLOOP)) == KEVENT_FLAG_DYNAMIC_KQUEUE)
+               return EINVAL;
+
+       if (flags & (KEVENT_FLAG_WORKLOOP_SERVICER_ATTACH | KEVENT_FLAG_WORKLOOP_SERVICER_DETACH |
+           KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST | KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST | KEVENT_FLAG_WORKLOOP_NO_WQ_THREAD)) {
+
+               /* allowed only on workloops when calling kevent_id from user-space */
+               if (!(flags & KEVENT_FLAG_WORKLOOP) || (flags & KEVENT_FLAG_KERNEL) || !(flags & KEVENT_FLAG_DYNAMIC_KQUEUE))
+                       return EINVAL;
+
+               /* cannot attach and detach simultaneously*/
+               if ((flags & KEVENT_FLAG_WORKLOOP_SERVICER_ATTACH) && (flags & KEVENT_FLAG_WORKLOOP_SERVICER_DETACH))
+                       return EINVAL;
+
+               /* cannot ask for events and detach */
+               if ((flags & KEVENT_FLAG_WORKLOOP_SERVICER_DETACH) && kevent_args_requesting_events(flags, nevents))
+                       return EINVAL;
+
+       }
+
+       /* prepare to deal with stack-wise allocation of out events */
+       if (flags & KEVENT_FLAG_STACK_EVENTS) {
+               int scale = ((flags & KEVENT_FLAG_LEGACY32) ? 
+                            (IS_64BIT_PROCESS(p) ? sizeof(struct user64_kevent) :
+                                                   sizeof(struct user32_kevent)) :
+                            ((flags & KEVENT_FLAG_LEGACY64) ? sizeof(struct kevent64_s) :
+                                                              sizeof(struct kevent_qos_s)));
+               ueventlist += nevents * scale;
+       }
+
+       /* convert timeout to absolute - if we have one (and not immediate) */
+       error = kevent_get_timeout(p, utimeout, flags, &atv);
+       if (error)
+               return error;
+       
+       /* copyin initial value of data residual from data_available */
+       error = kevent_get_data_size(p, data_available, flags, &data_size);
+       if (error)
+               return error;
+
+       /* get the kq we are going to be working on */
+       error = kevent_get_kq(p, id, flags, &fp, &fd, &kq);
+       if (error)
+               return error;
+
+       /* only bound threads can receive events on workloops */
+       if ((flags & KEVENT_FLAG_WORKLOOP) && kevent_args_requesting_events(flags, nevents)) {
+               ut = (uthread_t)get_bsdthread_info(thread);
+               if (ut->uu_kqueue_bound != kq) {
+                       error = EXDEV;
+                       goto out;
+               }
+
+       }
+
+       /* attach the current thread if necessary */
+       if (flags & KEVENT_FLAG_WORKLOOP_SERVICER_ATTACH) {
+               error = kevent_servicer_attach_thread(thread, flags, kq);
+               if (error)
+                       goto out;
+       }
+       else {
+               /* before processing events and committing to the system call, return an error if the thread cannot be detached when requested */
+               if (flags & KEVENT_FLAG_WORKLOOP_SERVICER_DETACH) {
+                       error = kevent_servicer_detach_preflight(thread, flags, kq);
+                       if (error)
+                               goto out;
+               }
+       }
+
+       if (id_out && kq && (flags & KEVENT_FLAG_WORKLOOP)) {
+               assert(kq->kq_state & KQ_WORKLOOP);
+               struct kqworkloop *kqwl;
+               kqwl = (struct kqworkloop *)kq;
+               *id_out = kqwl->kqwl_dynamicid;
+       }
+
+       /* register all the change requests the user provided... */
+       noutputs = 0;
+       while (nchanges > 0 && error == 0) {
+               error = kevent_copyin(&changelist, &kev, p, flags);
+               if (error)
+                       break;
+
+               /* Make sure user doesn't pass in any system flags */
+               kev.flags &= ~EV_SYSFLAGS;
+
+               kevent_register(kq, &kev, p);
+
+               if (nevents > 0 &&
+                   ((kev.flags & EV_ERROR) || (kev.flags & EV_RECEIPT))) {
+                       if (kev.flags & EV_RECEIPT) {
+                               kev.flags |= EV_ERROR;
+                               kev.data = 0;
+                       }
+                       error = kevent_copyout(&kev, &ueventlist, p, flags);
+                       if (error == 0) {
+                               nevents--;
+                               noutputs++;
+                       }
+               } else if (kev.flags & EV_ERROR) {
+                       error = kev.data;
+               }
+               nchanges--;
+       }
+
+       /* short-circuit the scan if we only want error events */
+       if (flags & KEVENT_FLAG_ERROR_EVENTS)
+               nevents = 0;
+
+       /* process pending events */
+       if (nevents > 0 && noutputs == 0 && error == 0) {
+               /* store the continuation/completion data in the uthread */
+               ut = (uthread_t)get_bsdthread_info(thread);
+               cont_args = &ut->uu_kevent.ss_kevent;
+               cont_args->fp = fp;
+               cont_args->fd = fd;
+               cont_args->retval = retval;
+               cont_args->eventlist = ueventlist;
+               cont_args->eventcount = nevents;
+               cont_args->eventout = noutputs;
+               cont_args->data_available = data_available;
+               cont_args->process_data.fp_fd = (int)id;
+               cont_args->process_data.fp_flags = flags;
+               cont_args->process_data.fp_data_out = data_out;
+               cont_args->process_data.fp_data_size = data_size;
+               cont_args->process_data.fp_data_resid = data_size;
+
+               error = kqueue_scan(kq, kevent_callback,
+                                   continuation, cont_args,
+                                   &cont_args->process_data,
+                                   &atv, p);
+
+               /* process remaining outputs */
+               noutputs = cont_args->eventout;
+               data_resid = cont_args->process_data.fp_data_resid;
+
+               /* copyout residual data size value (if it needs to be copied out) */
+               /* don't abandon other output just because of residual copyout failures */
+               if (error == 0 && data_available && data_resid != data_size) {
+                       (void)kevent_put_data_size(p, data_available, flags, data_resid);
+               }
+       }
+
+       /* detach the current thread if necessary */
+       if (flags & KEVENT_FLAG_WORKLOOP_SERVICER_DETACH) {
+               assert(fp == NULL);
+               kevent_servicer_detach_thread(p, id, thread, flags, kq);
+       }
+
+out:
+       kevent_put_kq(p, id, fp, kq);
+
+       /* don't restart after signals... */
+       if (error == ERESTART)
+               error = EINTR;
+       else if (error == EWOULDBLOCK)
+               error = 0;
+       if (error == 0)
+               *retval = noutputs;
+       return (error);
+}
+
+
+/*
+ * kevent_callback - callback for each individual event
+ *
+ * called with nothing locked
+ * caller holds a reference on the kqueue
+ */
+static int
+kevent_callback(__unused struct kqueue *kq, struct kevent_internal_s *kevp,
+    void *data)
+{
+       struct _kevent *cont_args;
+       int error;
+
+       cont_args = (struct _kevent *)data;
+       assert(cont_args->eventout < cont_args->eventcount);
+
+       /*
+        * Copy out the appropriate amount of event data for this user.
+        */
+       error = kevent_copyout(kevp, &cont_args->eventlist, current_proc(),
+                              cont_args->process_data.fp_flags);
+
+       /*
+        * If there isn't space for additional events, return
+        * a harmless error to stop the processing here
+        */
+       if (error == 0 && ++cont_args->eventout == cont_args->eventcount)
+               error = EWOULDBLOCK;
+       return (error);
+}
+
+/*
+ * kevent_description - format a description of a kevent for diagnostic output
+ *
+ * called with a 256-byte string buffer
+ */
+
+char *
+kevent_description(struct kevent_internal_s *kevp, char *s, size_t n)
+{
+       snprintf(s, n,
+           "kevent="
+           "{.ident=%#llx, .filter=%d, .flags=%#x, .udata=%#llx, .fflags=%#x, .data=%#llx, .ext[0]=%#llx, .ext[1]=%#llx}",
+           kevp->ident,
+           kevp->filter,
+           kevp->flags,
+           kevp->udata,
+           kevp->fflags,
+           kevp->data,
+           kevp->ext[0],
+           kevp->ext[1] );
+
+       return (s);
+}
+
+/*
+ * kevent_register - add a new event to a kqueue
+ *
+ *     Creates a mapping between the event source and
+ *     the kqueue via a knote data structure.
+ *
+ *     Because many/most the event sources are file
+ *     descriptor related, the knote is linked off
+ *     the filedescriptor table for quick access.
+ *
+ *     called with nothing locked
+ *     caller holds a reference on the kqueue
+ */
+
+void
+kevent_register(struct kqueue *kq, struct kevent_internal_s *kev,
+    __unused struct proc *ctxp)
+{
+       struct proc *p = kq->kq_p;
+       const struct filterops *fops;
+       struct knote *kn = NULL;
+       int result = 0;
+       int error = 0;
+       unsigned short kev_flags = kev->flags;
+       int knoteuse_flags = KNUSE_NONE;
+
+       if (kev->filter < 0) {
+               if (kev->filter + EVFILT_SYSCOUNT < 0) {
+                       error = EINVAL;
+                       goto out;
+               }
+               fops = sysfilt_ops[~kev->filter];       /* to 0-base index */
+       } else {
+               error = EINVAL;
+               goto out;
+       }
+
+       /* restrict EV_VANISHED to adding udata-specific dispatch kevents */
+       if ((kev->flags & EV_VANISHED) &&
+           (kev->flags & (EV_ADD | EV_DISPATCH2)) != (EV_ADD | EV_DISPATCH2)) {
+               error = EINVAL;
+               goto out;
+       }
+
+       /* Simplify the flags - delete and disable overrule */
+       if (kev->flags & EV_DELETE)
+               kev->flags &= ~EV_ADD;
+       if (kev->flags & EV_DISABLE)
+               kev->flags &= ~EV_ENABLE;
+
+       if (kq->kq_state & KQ_WORKLOOP) {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_REGISTER),
+                             ((struct kqworkloop *)kq)->kqwl_dynamicid,
+                             kev->udata, kev->flags, kev->filter);
+       } else if (kq->kq_state & KQ_WORKQ) {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_REGISTER),
+                             0, kev->udata, kev->flags, kev->filter);
+       } else {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_REGISTER),
+                             VM_KERNEL_UNSLIDE_OR_PERM(kq),
+                             kev->udata, kev->flags, kev->filter);
+       }
+
+restart:
+
+       /* find the matching knote from the fd tables/hashes */
+       kn = kq_find_knote_and_kq_lock(kq, kev, fops->f_isfd, p);
+
+       if (kn == NULL) {
+               if (kev->flags & EV_ADD) {
+                       struct fileproc *knote_fp = NULL;
+
+                       /* grab a file reference for the new knote */
+                       if (fops->f_isfd) {
+                               if ((error = fp_lookup(p, kev->ident, &knote_fp, 0)) != 0) {
+                                       goto out;
+                               }
+                       }
+
+                       kn = knote_alloc();
+                       if (kn == NULL) {
+                               error = ENOMEM;
+                               if (knote_fp != NULL)
+                                       fp_drop(p, kev->ident, knote_fp, 0);
+                               goto out;
+                       }
+
+                       kn->kn_fp = knote_fp;
+                       knote_set_kq(kn, kq);
+                       kqueue_retain(kq); /* retain a kq ref */
+                       kn->kn_filtid = ~kev->filter;
+                       kn->kn_inuse = 1;  /* for f_attach() */
+                       kn->kn_status = KN_ATTACHING | KN_ATTACHED;
+
+                       /* was vanish support requested */
+                       if (kev->flags & EV_VANISHED) {
+                               kev->flags &= ~EV_VANISHED;
+                               kn->kn_status |= KN_REQVANISH;
+                       }
+
+                       /* snapshot matching/dispatching protcol flags into knote */
+                       if (kev->flags & EV_DISPATCH)
+                               kn->kn_status |= KN_DISPATCH;
+                       if (kev->flags & EV_UDATA_SPECIFIC)
+                               kn->kn_status |= KN_UDATA_SPECIFIC;
+
+                       /*
+                        * copy the kevent state into knote
+                        * protocol is that fflags and data
+                        * are saved off, and cleared before
+                        * calling the attach routine.
+                        */
+                       kn->kn_kevent = *kev;
+                       kn->kn_sfflags = kev->fflags;
+                       kn->kn_sdata = kev->data;
+                       kn->kn_fflags = 0;
+                       kn->kn_data = 0;
+
+                       /* invoke pthread kext to convert kevent qos to thread qos */
+                       knote_canonicalize_kevent_qos(kn);
+                       knote_set_qos_index(kn, qos_index_from_qos(kn, kn->kn_qos, FALSE));
+
+                       /* before anyone can find it */
+                       if (kev->flags & EV_DISABLE) {
+                               /*
+                                * do this before anyone can find it,
+                                * this can't call knote_disable() because it expects having
+                                * the kqlock held
+                                */
+                               kn->kn_status |= KN_DISABLED;
+                       }
+
+                       /* Add the knote for lookup thru the fd table */
+                       error = kq_add_knote(kq, kn, kev, p, &knoteuse_flags);
+                       if (error) {
+                               (void)kqueue_release(kq, KQUEUE_CANT_BE_LAST_REF);
+                               knote_free(kn);
+                               if (knote_fp != NULL)
+                                       fp_drop(p, kev->ident, knote_fp, 0);
+
+                               if (error == ERESTART) {
+                                       error = 0;
+                                       goto restart;
+                               }
+                               goto out;
+                       }
+
+                       /* fp reference count now applies to knote */
+                       /* rwlock boost is now held */
+
+                       /* call filter attach routine */
+                       result = fops->f_attach(kn, kev);
+
+                       /*
+                        * Trade knote use count for kq lock.
+                        * Cannot be dropped because we held
+                        * KN_ATTACHING throughout.
+                        */
+                       knoteuse2kqlock(kq, kn, KNUSE_STEAL_DROP | knoteuse_flags);
+
+                       if (kn->kn_flags & EV_ERROR) {
+                               /*
+                                * Failed to attach correctly, so drop.
+                                * All other possible users/droppers
+                                * have deferred to us.  Save the error
+                                * to return to our caller.
+                                */
+                               kn->kn_status &= ~KN_ATTACHED;
+                               kn->kn_status |= KN_DROPPING;
+                               error = kn->kn_data;
+                               kqunlock(kq);
+                               knote_drop(kn, p);
+                               goto out;
+                       }
+
+                       /* end "attaching" phase - now just attached */
+                       kn->kn_status &= ~KN_ATTACHING;
+
+                       if (kn->kn_status & KN_DROPPING) {
+                               /*
+                                * Attach succeeded, but someone else
+                                * deferred their drop - now we have
+                                * to do it for them.
+                                */
+                               kqunlock(kq);
+                               knote_drop(kn, p);
+                               goto out;
+                       }
+
+                       /* Mark the thread request overcommit - if appropos */
+                       knote_set_qos_overcommit(kn);
+
+                       /*
+                        * If the attach routine indicated that an
+                        * event is already fired, activate the knote.
+                        */
+                       if (result)
+                               knote_activate(kn);
+
+                       if (knote_fops(kn)->f_post_attach) {
+                               error = knote_fops(kn)->f_post_attach(kn, kev);
+                               if (error) {
+                                       kqunlock(kq);
+                                       goto out;
+                               }
+                       }
+
+               } else {
+                       if ((kev_flags & (EV_ADD | EV_DELETE)) == (EV_ADD | EV_DELETE) &&
+                                       (kq->kq_state & KQ_WORKLOOP)) {
+                               /*
+                                * For workloops, understand EV_ADD|EV_DELETE as a "soft" delete
+                                * that doesn't care about ENOENT, so just pretend the deletion
+                                * happened.
+                                */
+                       } else {
+                               error = ENOENT;
+                       }
+                       goto out;
+               }
+
+       } else {
+               /* existing knote: kqueue lock already taken by kq_find_knote_and_kq_lock */
+
+               if ((kn->kn_status & (KN_DROPPING | KN_ATTACHING)) != 0) {
+                       /*
+                        * The knote is not in a stable state, wait for that
+                        * transition to complete and then redrive the lookup.
+                        */
+                       knoteusewait(kq, kn);
+                       goto restart;
+               }
+
+               if (kev->flags & EV_DELETE) {
+
+                       /*
+                        * If attempting to delete a disabled dispatch2 knote,
+                        * we must wait for the knote to be re-enabled (unless
+                        * it is being re-enabled atomically here).
+                        */
+                       if ((kev->flags & EV_ENABLE) == 0 &&
+                           (kn->kn_status & (KN_DISPATCH2 | KN_DISABLED)) ==
+                                            (KN_DISPATCH2 | KN_DISABLED)) {
+                               kn->kn_status |= KN_DEFERDELETE;
+                               kqunlock(kq);
+                               error = EINPROGRESS;
+                       } else if (knote_fops(kn)->f_drop_and_unlock) {
+                               /*
+                                * The filter has requested to handle EV_DELETE events
+                                *
+                                * ERESTART means the kevent has to be re-evaluated
+                                */
+                               error = knote_fops(kn)->f_drop_and_unlock(kn, kev);
+                               if (error == ERESTART) {
+                                       error = 0;
+                                       goto restart;
+                               }
+                       } else if (kqlock2knotedrop(kq, kn)) {
+                               /* standard/default EV_DELETE path */
+                               knote_drop(kn, p);
+                       } else {
+                               /*
+                                * The kqueue is unlocked, it's not being
+                                * dropped, and kqlock2knotedrop returned 0:
+                                * this means that someone stole the drop of
+                                * the knote from us.
+                                */
+                               error = EINPROGRESS;
+                       }
+                       goto out;
+               }
+
+               /*
+                * If we are re-enabling a deferred-delete knote,
+                * just enable it now and avoid calling the
+                * filter touch routine (it has delivered its
+                * last event already).
+                */
+               if ((kev->flags & EV_ENABLE) &&
+                   (kn->kn_status & KN_DEFERDELETE)) {
+                       assert(kn->kn_status & KN_DISABLED);
+                       knote_activate(kn);
+                       knote_enable(kn);
+                       kqunlock(kq);
+                       goto out;
+               }
+
+               /*
+                * If we are disabling, do it before unlocking and
+                * calling the touch routine (so no processing can
+                * see the new kevent state before the disable is
+                * applied).
+                */
+               if (kev->flags & EV_DISABLE)
+                       knote_disable(kn);
+
+               /*
+                * Convert the kqlock to a use reference on the
+                * knote so we can call the filter touch routine.
+                */
+               if (knoteuse_needs_boost(kn, kev)) {
+                       knoteuse_flags |= KNUSE_BOOST;
+               }
+               if (kqlock2knoteuse(kq, kn, knoteuse_flags)) {
+                       /*
+                        * Call touch routine to notify filter of changes
+                        * in filter values (and to re-determine if any
+                        * events are fired).
+                        */
+                       result = knote_fops(kn)->f_touch(kn, kev);
+
+                       /* Get the kq lock back (don't defer droppers). */
+                       if (!knoteuse2kqlock(kq, kn, knoteuse_flags)) {
+                               kqunlock(kq);
+                               goto out;
+                       }
+
+                       /* Handle errors during touch routine */
+                       if (kev->flags & EV_ERROR) {
+                               error = kev->data;
+                               kqunlock(kq);
+                               goto out;
+                       }
+
+                       /* Activate it if the touch routine said to */
+                       if (result)
+                               knote_activate(kn);
+               }
+
+               /* Enable the knote if called for */
+               if (kev->flags & EV_ENABLE)
+                       knote_enable(kn);
+
+       }
+
+       /* still have kqlock held and knote is valid */
+       kqunlock(kq);
+
+out:
+       /* output local errors through the kevent */
+       if (error) {
+               kev->flags |= EV_ERROR;
+               kev->data = error;
+       }
+}
+
+
+/*
+ * knote_process - process a triggered event
+ *
+ *     Validate that it is really still a triggered event
+ *     by calling the filter routines (if necessary).  Hold
+ *     a use reference on the knote to avoid it being detached.
+ *
+ *     If it is still considered triggered, we will have taken
+ *     a copy of the state under the filter lock.  We use that
+ *     snapshot to dispatch the knote for future processing (or
+ *     not, if this was a lost event).
+ *
+ *     Our caller assures us that nobody else can be processing
+ *     events from this knote during the whole operation. But
+ *     others can be touching or posting events to the knote
+ *     interspersed with our processing it.
+ *
+ *     caller holds a reference on the kqueue.
+ *     kqueue locked on entry and exit - but may be dropped
+ */
+static int
+knote_process(struct knote *kn,        
+       kevent_callback_t callback,
+       void *callback_data,
+       struct filt_process_s *process_data,
+       struct proc *p)
+{
+       struct kevent_internal_s kev;
+       struct kqueue *kq = knote_get_kq(kn);
+       int result = 0;
+       int error = 0;
+
+       bzero(&kev, sizeof(kev));
+
+       /*
+        * Must be active or stayactive
+        * Must be queued and not disabled/suppressed
+        */
+       assert(kn->kn_status & KN_QUEUED);
+       assert(kn->kn_status & (KN_ACTIVE|KN_STAYACTIVE));
+       assert(!(kn->kn_status & (KN_DISABLED|KN_SUPPRESSED|KN_DROPPING)));
+
+       if (kq->kq_state & KQ_WORKLOOP) {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS),
+                             ((struct kqworkloop *)kq)->kqwl_dynamicid,
+                             kn->kn_udata, kn->kn_status | (kn->kn_id << 32),
+                             kn->kn_filtid);
+       } else if (kq->kq_state & KQ_WORKQ) {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_PROCESS),
+                             0, kn->kn_udata, kn->kn_status | (kn->kn_id << 32),
+                             kn->kn_filtid);
+       } else {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS),
+                             VM_KERNEL_UNSLIDE_OR_PERM(kq), kn->kn_udata,
+                             kn->kn_status | (kn->kn_id << 32), kn->kn_filtid);
+       }
+
+       /*
+        * For deferred-drop or vanished events, we just create a fake
+        * event to acknowledge end-of-life.  Otherwise, we call the
+        * filter's process routine to snapshot the kevent state under
+        * the filter's locking protocol.
+        */
+       if (kn->kn_status & (KN_DEFERDELETE | KN_VANISHED)) {
+               /* create fake event */
+               kev.filter = kn->kn_filter;
+               kev.ident = kn->kn_id;
+               kev.qos = kn->kn_qos;
+               kev.flags = (kn->kn_status & KN_DEFERDELETE) ? 
+                           EV_DELETE : EV_VANISHED;
+               kev.flags |= (EV_DISPATCH2 | EV_ONESHOT);
+               kev.udata = kn->kn_udata;
+               result = 1;
+
+               knote_suppress(kn);
+       } else {
+               int flags = KNUSE_NONE;
+               /* deactivate - so new activations indicate a wakeup */
+               knote_deactivate(kn);
+
+               /* suppress knotes to avoid returning the same event multiple times in a single call. */
+               knote_suppress(kn);
+
+               if (knoteuse_needs_boost(kn, NULL)) {
+                       flags |= KNUSE_BOOST;
+               }
+               /* convert lock to a knote use reference */
+               if (!kqlock2knoteuse(kq, kn, flags))
+                       panic("dropping knote found on queue\n");
+
+               /* call out to the filter to process with just a ref */
+               result = knote_fops(kn)->f_process(kn, process_data, &kev);
+               if (result) flags |= KNUSE_STEAL_DROP;
+
+               /*
+                * convert our reference back to a lock. accept drop
+                * responsibility from others if we've committed to
+                * delivering event data.
+                */
+               if (!knoteuse2kqlock(kq, kn, flags)) {
+                       /* knote dropped */
+                       kn = NULL;
+               }
+       }
+
+       if (kn != NULL) {
+               /*
+                * Determine how to dispatch the knote for future event handling.
+                * not-fired: just return (do not callout, leave deactivated).
+                * One-shot:  If dispatch2, enter deferred-delete mode (unless this is
+                *            is the deferred delete event delivery itself).  Otherwise,
+                *            drop it.
+                * stolendrop:We took responsibility for someone else's drop attempt.
+                *            treat this just like one-shot and prepare to turn it back
+                *            into a deferred delete if required.
+                * Dispatch:  don't clear state, just mark it disabled.
+                * Cleared:   just leave it deactivated.
+                * Others:    re-activate as there may be more events to handle.
+                *            This will not wake up more handlers right now, but
+                *            at the completion of handling events it may trigger
+                *            more handler threads (TODO: optimize based on more than
+                *            just this one event being detected by the filter).
+                */
+
+               if (result == 0)
+                       return (EJUSTRETURN);
+
+               if ((kev.flags & EV_ONESHOT) || (kn->kn_status & KN_STOLENDROP)) {
+                       if ((kn->kn_status & (KN_DISPATCH2 | KN_DEFERDELETE)) == KN_DISPATCH2) {
+                               /* defer dropping non-delete oneshot dispatch2 events */
+                               kn->kn_status |= KN_DEFERDELETE;
+                               knote_disable(kn);
+
+                               /* if we took over another's drop clear those flags here */
+                               if (kn->kn_status & KN_STOLENDROP) {
+                                       assert(kn->kn_status & KN_DROPPING);
+                                       /*
+                                        * the knote will be dropped when the
+                                        * deferred deletion occurs
+                                        */
+                                       kn->kn_status &= ~(KN_DROPPING|KN_STOLENDROP);
+                               }
+                       } else if (kn->kn_status & KN_STOLENDROP) {
+                               /* We now own the drop of the knote. */
+                               assert(kn->kn_status & KN_DROPPING);
+                               knote_unsuppress(kn);
+                               kqunlock(kq);
+                               knote_drop(kn, p);
+                               kqlock(kq);
+                       } else if (kqlock2knotedrop(kq, kn)) {
+                               /* just EV_ONESHOT, _not_ DISPATCH2 */
+                               knote_drop(kn, p);
+                               kqlock(kq);
+                       }
+               } else if (kn->kn_status & KN_DISPATCH) {
+                       /* disable all dispatch knotes */
+                       knote_disable(kn);
+               } else if ((kev.flags & EV_CLEAR) == 0) {
+                       /* re-activate in case there are more events */
+                       knote_activate(kn);
+               }
+       }
+
+       /*
+        * callback to handle each event as we find it.
+        * If we have to detach and drop the knote, do
+        * it while we have the kq unlocked.
+        */
+       if (result) {
+               kqunlock(kq);
+               error = (callback)(kq, &kev, callback_data);
+               kqlock(kq);
+       }
+       return (error);
+}
+
+
+/*
+ * Return 0 to indicate that processing should proceed,
+ * -1 if there is nothing to process.
+ *
+ * Called with kqueue locked and returns the same way,
+ * but may drop lock temporarily.
+ */
+static int
+kqworkq_begin_processing(struct kqworkq *kqwq, kq_index_t qos_index, int flags)
+{
+       struct kqrequest *kqr;
+       thread_t self = current_thread();
+       __assert_only struct uthread *ut = get_bsdthread_info(self);
+
+       assert(kqwq->kqwq_state & KQ_WORKQ);
+       assert(qos_index < KQWQ_NQOS);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_PROCESS_BEGIN) | DBG_FUNC_START,
+                     flags, qos_index);
+
+       kqwq_req_lock(kqwq);
+
+       kqr = kqworkq_get_request(kqwq, qos_index);
+
+       /* manager skips buckets that haven't asked for its help */
+       if (flags & KEVENT_FLAG_WORKQ_MANAGER) {
+
+               /* If nothing for manager to do, just return */
+               if ((kqr->kqr_state & KQWQ_THMANAGER) == 0) {
+                       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_PROCESS_BEGIN) | DBG_FUNC_END,
+                                               0, kqr->kqr_state);
+                       kqwq_req_unlock(kqwq);
+                       return -1;
+               }
+               /* bind manager thread from this time on */
+               kqworkq_bind_thread_impl(kqwq, qos_index, self, flags);
+
+       } else {
+               /* We should already be bound to this kqueue */
+               assert(kqr->kqr_state & KQR_BOUND);
+               assert(kqr->kqr_thread == self);
+               assert(ut->uu_kqueue_bound == (struct kqueue *)kqwq);
+               assert(ut->uu_kqueue_qos_index == qos_index);
+               assert((ut->uu_kqueue_flags & flags) == ut->uu_kqueue_flags);
+       }
+
+       /*
+        * we should have been requested to be here
+        * and nobody else should still be processing
+        */
+       assert(kqr->kqr_state & KQR_WAKEUP);
+       assert(kqr->kqr_state & KQR_THREQUESTED);
+       assert((kqr->kqr_state & KQR_PROCESSING) == 0);
+
+       /* reset wakeup trigger to catch new events after we start processing */
+       kqr->kqr_state &= ~KQR_WAKEUP;
+
+       /* convert to processing mode */
+       kqr->kqr_state |= KQR_PROCESSING;
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_PROCESS_BEGIN) | DBG_FUNC_END,
+                     kqr_thread_id(kqr), kqr->kqr_state);
+
+       kqwq_req_unlock(kqwq);
+       return 0;
+}
+
+static inline bool
+kqworkloop_is_processing_on_current_thread(struct kqworkloop *kqwl)
+{
+       struct kqueue *kq = &kqwl->kqwl_kqueue;
+
+       kqlock_held(kq);
+
+       if (kq->kq_state & KQ_PROCESSING) {
+               /*
+                * KQ_PROCESSING is unset with the kqlock held, and the kqr thread is
+                * never modified while KQ_PROCESSING is set, meaning that peeking at
+                * its value is safe from this context.
+                */
+               return kqwl->kqwl_request.kqr_thread == current_thread();
+       }
+       return false;
+}
+
+static void
+kqworkloop_acknowledge_events(struct kqworkloop *kqwl, boolean_t clear_ipc_override)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       struct knote *kn, *tmp;
+
+       kqlock_held(&kqwl->kqwl_kqueue);
+
+       TAILQ_FOREACH_SAFE(kn, &kqr->kqr_suppressed, kn_tqe, tmp) {
+               /*
+                * If a knote that can adjust QoS is disabled because of the automatic
+                * behavior of EV_DISPATCH, the knotes should stay suppressed so that
+                * further overrides keep pushing.
+                */
+               if (knote_fops(kn)->f_adjusts_qos && (kn->kn_status & KN_DISABLED) &&
+                               (kn->kn_status & (KN_STAYACTIVE | KN_DROPPING)) == 0 &&
+                               (kn->kn_flags & (EV_DISPATCH | EV_DISABLE)) == EV_DISPATCH) {
+                       /*
+                        * When called from unbind, clear the sync ipc override on the knote
+                        * for events which are delivered.
+                        */
+                       if (clear_ipc_override) {
+                               knote_adjust_sync_qos(kn, THREAD_QOS_UNSPECIFIED, FALSE);
+                       }
+                       continue;
+               }
+               knote_unsuppress(kn);
+       }
+}
+
+static int
+kqworkloop_begin_processing(struct kqworkloop *kqwl,
+               __assert_only unsigned int flags)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       struct kqueue *kq = &kqwl->kqwl_kqueue;
+
+       kqlock_held(kq);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_BEGIN) | DBG_FUNC_START,
+                     kqwl->kqwl_dynamicid, flags, 0);
+
+       kqwl_req_lock(kqwl);
+
+       /* nobody else should still be processing */
+       assert((kqr->kqr_state & KQR_PROCESSING) == 0);
+       assert((kq->kq_state & KQ_PROCESSING) == 0);
+
+       kqr->kqr_state |= KQR_PROCESSING | KQR_R2K_NOTIF_ARMED;
+       kq->kq_state |= KQ_PROCESSING;
+
+       kqwl_req_unlock(kqwl);
+
+       kqworkloop_acknowledge_events(kqwl, FALSE);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_BEGIN) | DBG_FUNC_END,
+                     kqwl->kqwl_dynamicid, flags, 0);
+
+       return 0;
+}
+
+/*
+ * Return 0 to indicate that processing should proceed,
+ * -1 if there is nothing to process.
+ *
+ * Called with kqueue locked and returns the same way,
+ * but may drop lock temporarily.
+ * May block.
+ */
+static int
+kqueue_begin_processing(struct kqueue *kq, kq_index_t qos_index, unsigned int flags)
+{
+       struct kqtailq *suppressq;
+
+       kqlock_held(kq);
+
+       if (kq->kq_state & KQ_WORKQ) {
+               return kqworkq_begin_processing((struct kqworkq *)kq, qos_index, flags);
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               return kqworkloop_begin_processing((struct kqworkloop*)kq, flags);
+       }
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_BEGIN) | DBG_FUNC_START,
+                     VM_KERNEL_UNSLIDE_OR_PERM(kq), flags);
+
+       assert(qos_index == QOS_INDEX_KQFILE);
+
+       /* wait to become the exclusive processing thread */
+       for (;;) {
+               if (kq->kq_state & KQ_DRAIN) {
+                       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_BEGIN) | DBG_FUNC_END,
+                                     VM_KERNEL_UNSLIDE_OR_PERM(kq), 2);
+                       return -1;
+               }
+
+               if ((kq->kq_state & KQ_PROCESSING) == 0)
+                       break;
+
+               /* if someone else is processing the queue, wait */
+               kq->kq_state |= KQ_PROCWAIT;
+               suppressq = kqueue_get_suppressed_queue(kq, qos_index);
+               waitq_assert_wait64((struct waitq *)&kq->kq_wqs,
+                                   CAST_EVENT64_T(suppressq),
+                                   THREAD_UNINT, TIMEOUT_WAIT_FOREVER);
+               
+               kqunlock(kq);
+               thread_block(THREAD_CONTINUE_NULL);
+               kqlock(kq);
+       }
+
+       /* Nobody else processing */
+
+       /* clear pre-posts and KQ_WAKEUP now, in case we bail early */
+       waitq_set_clear_preposts(&kq->kq_wqs);
+       kq->kq_state &= ~KQ_WAKEUP;
+
+       /* anything left to process? */
+       if (kqueue_queue_empty(kq, qos_index)) {
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_BEGIN) | DBG_FUNC_END,
+                             VM_KERNEL_UNSLIDE_OR_PERM(kq), 1);
+               return -1;
+       }
+
+       /* convert to processing mode */
+       kq->kq_state |= KQ_PROCESSING;
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_BEGIN) | DBG_FUNC_END,
+                     VM_KERNEL_UNSLIDE_OR_PERM(kq));
+
+       return 0;
+}
+
+/*
+ *     kqworkq_end_processing - Complete the processing of a workq kqueue
+ *
+ *     We may have to request new threads.
+ *     This can happen there are no waiting processing threads and:
+ *     - there were active events we never got to (count > 0)
+ *     - we pended waitq hook callouts during processing
+ *     - we pended wakeups while processing (or unsuppressing)
+ *
+ *     Called with kqueue lock held.
+ */
+static void
+kqworkq_end_processing(struct kqworkq *kqwq, kq_index_t qos_index, int flags)
+{
+#pragma unused(flags)
+
+       struct kqueue *kq = &kqwq->kqwq_kqueue;
+       struct kqtailq *suppressq = kqueue_get_suppressed_queue(kq, qos_index);
+
+       thread_t self = current_thread();
+       struct uthread *ut = get_bsdthread_info(self);
+       struct knote *kn;
+       struct kqrequest *kqr;
+       thread_t thread;
+
+       assert(kqwq->kqwq_state & KQ_WORKQ);
+       assert(qos_index < KQWQ_NQOS);
+
+       /* Are we really bound to this kqueue? */
+       if (ut->uu_kqueue_bound != kq) {
+               assert(ut->uu_kqueue_bound == kq);
+               return;
+       }
+
+       kqr = kqworkq_get_request(kqwq, qos_index);
+
+       kqwq_req_lock(kqwq);
+
+       /* Do we claim to be manager? */
+       if (flags & KEVENT_FLAG_WORKQ_MANAGER) {
+
+               /* bail if not bound that way */
+               if (ut->uu_kqueue_qos_index != KQWQ_QOS_MANAGER ||
+                   (ut->uu_kqueue_flags & KEVENT_FLAG_WORKQ_MANAGER) == 0) {
+                       assert(ut->uu_kqueue_qos_index == KQWQ_QOS_MANAGER);
+                       assert(ut->uu_kqueue_flags & KEVENT_FLAG_WORKQ_MANAGER);
+                       kqwq_req_unlock(kqwq);
+                       return;
+               }
+
+               /* bail if this request wasn't already getting manager help */
+               if ((kqr->kqr_state & KQWQ_THMANAGER) == 0 ||
+                   (kqr->kqr_state & KQR_PROCESSING) == 0) {
+                       kqwq_req_unlock(kqwq);
+                       return;
+               }
+       } else {
+               if (ut->uu_kqueue_qos_index != qos_index ||
+                   (ut->uu_kqueue_flags & KEVENT_FLAG_WORKQ_MANAGER)) {
+                       assert(ut->uu_kqueue_qos_index == qos_index);
+                       assert((ut->uu_kqueue_flags & KEVENT_FLAG_WORKQ_MANAGER) == 0);
+                       kqwq_req_unlock(kqwq);
+                       return;
+               }
+       }
+
+       assert(kqr->kqr_state & KQR_BOUND);
+       thread = kqr->kqr_thread;
+       assert(thread == self);
+
+       assert(kqr->kqr_state & KQR_PROCESSING);
+
+       /* If we didn't drain the whole queue, re-mark a wakeup being needed */
+       if (!kqueue_queue_empty(kq, qos_index))
+               kqr->kqr_state |= KQR_WAKEUP;
+
+       kqwq_req_unlock(kqwq);
+
+       /*
+        * Return suppressed knotes to their original state.
+        * For workq kqueues, suppressed ones that are still
+        * truly active (not just forced into the queue) will
+        * set flags we check below to see if anything got
+        * woken up.
+        */
+       while ((kn = TAILQ_FIRST(suppressq)) != NULL) {
+               assert(kn->kn_status & KN_SUPPRESSED);
+               knote_unsuppress(kn);
+       }
+
+       kqwq_req_lock(kqwq);
+
+       /* Indicate that we are done processing this request */
+       kqr->kqr_state &= ~KQR_PROCESSING;
+
+       /*
+        * Drop our association with this one request and its
+        * override on us.
+        */
+       kqworkq_unbind_thread(kqwq, qos_index, thread, flags);
+
+       /*
+        * request a new thread if we didn't process the whole
+        * queue or real events have happened (not just putting
+        * stay-active events back).
+        */
+       if (kqr->kqr_state & KQR_WAKEUP) {
+               if (kqueue_queue_empty(kq, qos_index)) {
+                       kqr->kqr_state &= ~KQR_WAKEUP;
+               } else {
+                       kqworkq_request_thread(kqwq, qos_index);
+               }
+       }
+       kqwq_req_unlock(kqwq);
+}
+
+static void
+kqworkloop_end_processing(struct kqworkloop *kqwl, int nevents,
+               unsigned int flags)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       struct kqueue *kq = &kqwl->kqwl_kqueue;
+
+       kqlock_held(kq);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_END) | DBG_FUNC_START,
+                       kqwl->kqwl_dynamicid, flags, 0);
+
+       if ((kq->kq_state & KQ_NO_WQ_THREAD) && nevents == 0 &&
+                       (flags & KEVENT_FLAG_IMMEDIATE) == 0) {
+               /*
+                * <rdar://problem/31634014> We may soon block, but have returned no
+                * kevents that need to be kept supressed for overriding purposes.
+                *
+                * It is hence safe to acknowledge events and unsuppress everything, so
+                * that if we block we can observe all events firing.
+                */
+               kqworkloop_acknowledge_events(kqwl, TRUE);
+       }
+
+       kqwl_req_lock(kqwl);
+
+       assert(kqr->kqr_state & KQR_PROCESSING);
+       assert(kq->kq_state & KQ_PROCESSING);
+
+       kq->kq_state &= ~KQ_PROCESSING;
+       kqr->kqr_state &= ~KQR_PROCESSING;
+       kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_RECOMPUTE_WAKEUP_QOS, 0);
+
+       kqwl_req_unlock(kqwl);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_END) | DBG_FUNC_END,
+                       kqwl->kqwl_dynamicid, flags, 0);
+}
+
+/*
+ * Called with kqueue lock held.
+ */
+static void
+kqueue_end_processing(struct kqueue *kq, kq_index_t qos_index,
+               int nevents, unsigned int flags)
+{
+       struct knote *kn;
+       struct kqtailq *suppressq;
+       int procwait;
+
+       kqlock_held(kq);
+
+       assert((kq->kq_state & KQ_WORKQ) == 0);
+
+       if (kq->kq_state & KQ_WORKLOOP) {
+               return kqworkloop_end_processing((struct kqworkloop *)kq, nevents, flags);
+       }
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_END),
+                     VM_KERNEL_UNSLIDE_OR_PERM(kq), flags);
+
+       assert(qos_index == QOS_INDEX_KQFILE);
+
+       /*
+        * Return suppressed knotes to their original state.
+        */
+       suppressq = kqueue_get_suppressed_queue(kq, qos_index);
+       while ((kn = TAILQ_FIRST(suppressq)) != NULL) {
+               assert(kn->kn_status & KN_SUPPRESSED);
+               knote_unsuppress(kn);
+       }
+
+       procwait = (kq->kq_state & KQ_PROCWAIT);
+       kq->kq_state &= ~(KQ_PROCESSING | KQ_PROCWAIT);
+
+       if (procwait) {
+               /* first wake up any thread already waiting to process */
+               waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                  CAST_EVENT64_T(suppressq),
+                                  THREAD_AWAKENED,
+                                  WAITQ_ALL_PRIORITIES);
+       }
+}
+
+/*
+ *     kqwq_internal_bind - bind thread to processing workq kqueue
+ *
+ *     Determines if the provided thread will be responsible for
+ *     servicing the particular QoS class index specified in the
+ *     parameters. Once the binding is done, any overrides that may
+ *     be associated with the cooresponding events can be applied.
+ *
+ *     This should be called as soon as the thread identity is known,
+ *     preferably while still at high priority during creation.
+ *
+ *  - caller holds a reference on the process (and workq kq)
+ *     - the thread MUST call kevent_qos_internal after being bound
+ *       or the bucket of events may never be delivered.  
+ *     - Nothing locked
+ *    (unless this is a synchronous bind, then the request is locked)
+ */
+static int
+kqworkq_internal_bind(
+       struct proc *p,
+       kq_index_t qos_index,
+       thread_t thread,
+       unsigned int flags)
+{
+       struct kqueue *kq;
+       struct kqworkq *kqwq;
+       struct kqrequest *kqr;
+       struct uthread *ut = get_bsdthread_info(thread);
+
+       /* If no process workq, can't be our thread. */
+       kq = p->p_fd->fd_wqkqueue;
+
+       if (kq == NULL)
+               return 0;
+
+       assert(kq->kq_state & KQ_WORKQ);
+       kqwq = (struct kqworkq *)kq;
+
+       /*
+        * No need to bind the manager thread to any specific
+        * bucket, but still claim the thread.
+        */
+       if (qos_index == KQWQ_QOS_MANAGER) {
+               assert(ut->uu_kqueue_bound == NULL);
+               assert(flags & KEVENT_FLAG_WORKQ_MANAGER);
+               ut->uu_kqueue_bound = kq;
+               ut->uu_kqueue_qos_index = qos_index;
+               ut->uu_kqueue_flags = flags;
+
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_BIND),
+                             thread_tid(thread), flags, qos_index);
+
+               return 1;
+       }
+
+       /*
+        * If this is a synchronous bind callback, the request
+        * lock is already held, so just do the bind.
+        */
+       if (flags & KEVENT_FLAG_SYNCHRONOUS_BIND) {
+               kqwq_req_held(kqwq);
+               /* strip out synchronout bind flag */
+               flags &= ~KEVENT_FLAG_SYNCHRONOUS_BIND;
+               kqworkq_bind_thread_impl(kqwq, qos_index, thread, flags);
+               return 1;
+       }
+
+       /*
+        * check the request that corresponds to our qos_index
+        * to see if there is an outstanding request.
+        */
+       kqr = kqworkq_get_request(kqwq, qos_index);
+       assert(kqr->kqr_qos_index == qos_index);
+       kqwq_req_lock(kqwq);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_BIND),
+                     thread_tid(thread), flags, qos_index, kqr->kqr_state);
+
+       if ((kqr->kqr_state & KQR_THREQUESTED) &&
+           (kqr->kqr_state & KQR_PROCESSING) == 0) {
+
+               if ((kqr->kqr_state & KQR_BOUND) &&
+                   thread == kqr->kqr_thread) {
+                       /* duplicate bind - claim the thread */
+                       assert(ut->uu_kqueue_bound == kq);
+                       assert(ut->uu_kqueue_qos_index == qos_index);
+                       kqwq_req_unlock(kqwq);
+                       return 1;
+               }
+               if ((kqr->kqr_state & (KQR_BOUND | KQWQ_THMANAGER)) == 0) {
+                       /* ours to bind to */
+                       kqworkq_bind_thread_impl(kqwq, qos_index, thread, flags);
+                       kqwq_req_unlock(kqwq);
+                       return 1;
+               }
+       }
+       kqwq_req_unlock(kqwq);
+       return 0;
+}
+
+static void
+kqworkloop_bind_thread_impl(struct kqworkloop *kqwl,
+                            thread_t thread,
+                            __assert_only unsigned int flags)
+{
+       assert(flags & KEVENT_FLAG_WORKLOOP);
+
+       /* the request object must be locked */
+       kqwl_req_held(kqwl);
+
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       struct uthread *ut = get_bsdthread_info(thread);
+       boolean_t ipc_override_is_sync;
+       kq_index_t qos_index = kqworkloop_combined_qos(kqwl, &ipc_override_is_sync);
+
+       /* nobody else bound so finally bind (as a workloop) */
+       assert(kqr->kqr_state & KQR_THREQUESTED);
+       assert((kqr->kqr_state & (KQR_BOUND | KQR_PROCESSING)) == 0);
+       assert(thread != kqwl->kqwl_owner);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_BIND),
+                     kqwl->kqwl_dynamicid, (uintptr_t)thread_tid(thread),
+                     qos_index,
+                     (uintptr_t)(((uintptr_t)kqr->kqr_override_index << 16) |
+                     (((uintptr_t)kqr->kqr_state) << 8) |
+                     ((uintptr_t)ipc_override_is_sync)));
+
+       kqr->kqr_state |= KQR_BOUND | KQR_R2K_NOTIF_ARMED;
+       kqr->kqr_thread = thread;
+
+       /* bind the workloop to the uthread */
+       ut->uu_kqueue_bound = (struct kqueue *)kqwl;
+       ut->uu_kqueue_flags = flags;
+       ut->uu_kqueue_qos_index = qos_index;
+       assert(ut->uu_kqueue_override_is_sync == 0);
+       ut->uu_kqueue_override_is_sync = ipc_override_is_sync;
+       if (qos_index) {
+               thread_add_ipc_override(thread, qos_index);
+       }
+       if (ipc_override_is_sync) {
+               thread_add_sync_ipc_override(thread);
+       }
+}
+
+/*
+ *  workloop_fulfill_threadreq - bind thread to processing workloop
+ *
+ * The provided thread will be responsible for delivering events
+ * associated with the given kqrequest.  Bind it and get ready for
+ * the thread to eventually arrive.
+ *
+ * If WORKLOOP_FULFILL_THREADREQ_SYNC is specified, the callback
+ * within the context of the pthread_functions->workq_threadreq
+ * callout.  In this case, the request structure is already locked.
+ */
+int
+workloop_fulfill_threadreq(struct proc *p,
+                           workq_threadreq_t req,
+                           thread_t thread,
+                           int flags)
+{
+       int sync = (flags & WORKLOOP_FULFILL_THREADREQ_SYNC);
+       int cancel = (flags & WORKLOOP_FULFILL_THREADREQ_CANCEL);
+       struct kqrequest *kqr;
+       struct kqworkloop *kqwl;
+
+       kqwl = (struct kqworkloop *)((uintptr_t)req -
+                                    offsetof(struct kqworkloop, kqwl_request) -
+                                    offsetof(struct kqrequest, kqr_req));
+       kqr = &kqwl->kqwl_request;
+
+       /* validate we're looking at something valid */
+       if (kqwl->kqwl_p != p ||
+           (kqwl->kqwl_state & KQ_WORKLOOP) == 0) {
+               assert(kqwl->kqwl_p == p);
+               assert(kqwl->kqwl_state & KQ_WORKLOOP);
+               return EINVAL;
+       }
+       
+       if (!sync)
+               kqwl_req_lock(kqwl);
+
+       /* Should be a pending request */
+       if ((kqr->kqr_state & KQR_BOUND) ||
+           (kqr->kqr_state & KQR_THREQUESTED) == 0) {
+
+               assert((kqr->kqr_state & KQR_BOUND) == 0);
+               assert(kqr->kqr_state & KQR_THREQUESTED);
+               if (!sync)
+                       kqwl_req_unlock(kqwl);
+               return EINPROGRESS;
+       }
+
+       assert((kqr->kqr_state & KQR_DRAIN) == 0);
+
+       /*
+        * Is it a cancel indication from pthread.
+        * If so, we must be exiting/exec'ing. Forget
+        * our pending request.
+        */
+       if (cancel) {
+               kqr->kqr_state &= ~KQR_THREQUESTED;
+               kqr->kqr_state |= KQR_DRAIN;
+       } else {
+               /* do the actual bind? */
+               kqworkloop_bind_thread_impl(kqwl, thread, KEVENT_FLAG_WORKLOOP);
+       }
+
+       if (!sync)
+               kqwl_req_unlock(kqwl);
+
+       if (cancel)
+               kqueue_release_last(p, &kqwl->kqwl_kqueue); /* may dealloc kq */
+
+       return 0;
+}
+       
+
+/*
+ *     kevent_qos_internal_bind - bind thread to processing kqueue
+ *
+ *     Indicates that the provided thread will be responsible for
+ *     servicing the particular QoS class index specified in the
+ *     parameters. Once the binding is done, any overrides that may
+ *     be associated with the cooresponding events can be applied.
+ *
+ *     This should be called as soon as the thread identity is known,
+ *     preferably while still at high priority during creation.
+ *
+ *  - caller holds a reference on the kqueue.
+ *     - the thread MUST call kevent_qos_internal after being bound
+ *       or the bucket of events may never be delivered.  
+ *     - Nothing locked (may take mutex or block).
+ */
+
+int
+kevent_qos_internal_bind(
+       struct proc *p,
+       int qos_class,
+       thread_t thread,
+       unsigned int flags)
+{
+       kq_index_t qos_index;
+
+       assert(flags & KEVENT_FLAG_WORKQ);
+
+       if (thread == THREAD_NULL || (flags & KEVENT_FLAG_WORKQ) == 0) {
+               return EINVAL;
+       }
+
+       /* get the qos index we're going to service */
+       qos_index = qos_index_for_servicer(qos_class, thread, flags);
+
+       if (kqworkq_internal_bind(p, qos_index, thread, flags))
+               return 0;
+
+       return EINPROGRESS;
+}
+
+
+static void
+kqworkloop_internal_unbind(
+       struct proc *p,
+       thread_t thread,
+       unsigned int flags)
+{
+       struct kqueue *kq;
+       struct kqworkloop *kqwl;
+       struct uthread *ut = get_bsdthread_info(thread);
+
+       assert(ut->uu_kqueue_bound != NULL);
+       kq = ut->uu_kqueue_bound;
+       assert(kq->kq_state & KQ_WORKLOOP);
+       kqwl = (struct kqworkloop *)kq;
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_UNBIND),
+                     kqwl->kqwl_dynamicid, (uintptr_t)thread_tid(thread),
+                     flags, 0);
+
+       if (!(kq->kq_state & KQ_NO_WQ_THREAD)) {
+               assert(is_workqueue_thread(thread));
+
+               kqlock(kq);
+               kqworkloop_unbind_thread(kqwl, thread, flags);
+               kqunlock(kq);
+
+               /* If last reference, dealloc the workloop kq */
+               kqueue_release_last(p, kq);
+       } else {
+               assert(!is_workqueue_thread(thread));
+               kevent_servicer_detach_thread(p, kqwl->kqwl_dynamicid, thread, flags, kq);
+       }
+}
+
+static void
+kqworkq_internal_unbind(
+       struct proc *p,
+       kq_index_t qos_index,
+       thread_t thread,
+       unsigned int flags)
+{
+       struct kqueue *kq;
+       struct kqworkq *kqwq;
+       struct uthread *ut;
+       kq_index_t end_index;
+
+       assert(thread == current_thread());
+       ut = get_bsdthread_info(thread);
+
+       kq = p->p_fd->fd_wqkqueue;
+       assert(kq->kq_state & KQ_WORKQ);
+       assert(ut->uu_kqueue_bound == kq);
+
+       kqwq = (struct kqworkq *)kq;
+
+       /* end servicing any requests we might own */
+       end_index = (qos_index == KQWQ_QOS_MANAGER) ? 
+           0 : qos_index;
+       kqlock(kq);
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_UNBIND),
+                     (uintptr_t)thread_tid(thread), flags, qos_index);
+
+       do {
+               kqworkq_end_processing(kqwq, qos_index, flags);
+       } while (qos_index-- > end_index);
+
+       ut->uu_kqueue_bound = NULL;
+       ut->uu_kqueue_qos_index = 0;
+       ut->uu_kqueue_flags = 0;
+
+       kqunlock(kq);
+}
+
+/*
+ *     kevent_qos_internal_unbind - unbind thread from processing kqueue
+ *
+ *     End processing the per-QoS bucket of events and allow other threads
+ *     to be requested for future servicing.  
+ *
+ *     caller holds a reference on the kqueue.
+ *     thread is the current thread.
+ */
+
+int
+kevent_qos_internal_unbind(
+       struct proc *p,
+       int qos_class,
+       thread_t thread,
+       unsigned int flags)
+{
+#pragma unused(qos_class)
+
+       struct uthread *ut;
+       struct kqueue *kq;
+       unsigned int bound_flags;
+       bool check_flags;
+
+       ut = get_bsdthread_info(thread);
+       if (ut->uu_kqueue_bound == NULL) {
+               /* early out if we are already unbound */
+               assert(ut->uu_kqueue_flags == 0);
+               assert(ut->uu_kqueue_qos_index == 0);
+               assert(ut->uu_kqueue_override_is_sync == 0);
+               return EALREADY;
+       }
+
+       assert(flags & (KEVENT_FLAG_WORKQ | KEVENT_FLAG_WORKLOOP));
+       assert(thread == current_thread());
+
+       check_flags = flags & KEVENT_FLAG_UNBIND_CHECK_FLAGS;
+
+       /* Get the kqueue we started with */
+       kq = ut->uu_kqueue_bound;
+       assert(kq != NULL);
+       assert(kq->kq_state & (KQ_WORKQ | KQ_WORKLOOP));
+
+       /* get flags and QoS parameters we started with */
+       bound_flags = ut->uu_kqueue_flags;
+
+       /* Unbind from the class of workq */
+       if (kq->kq_state & KQ_WORKQ) {
+               if (check_flags && !(flags & KEVENT_FLAG_WORKQ)) {
+                       return EINVAL;
+               }
+
+               kqworkq_internal_unbind(p, ut->uu_kqueue_qos_index, thread, bound_flags);
+       } else {
+               if (check_flags && !(flags & KEVENT_FLAG_WORKLOOP)) {
+                       return EINVAL;
+               }
+
+               kqworkloop_internal_unbind(p, thread, bound_flags);
+       }
+
+       return 0;
+}
+
+/*
+ * kqueue_process - process the triggered events in a kqueue
+ *
+ *     Walk the queued knotes and validate that they are
+ *     really still triggered events by calling the filter
+ *     routines (if necessary).  Hold a use reference on
+ *     the knote to avoid it being detached. For each event
+ *     that is still considered triggered, invoke the
+ *     callback routine provided.
+ *
+ *     caller holds a reference on the kqueue.
+ *     kqueue locked on entry and exit - but may be dropped
+ *     kqueue list locked (held for duration of call)
+ */
+
+static int
+kqueue_process(struct kqueue *kq,
+    kevent_callback_t callback,
+    void *callback_data,
+    struct filt_process_s *process_data,
+    int *countp,
+    struct proc *p)
+{
+       unsigned int flags = process_data ? process_data->fp_flags : 0;
+       struct uthread *ut = get_bsdthread_info(current_thread());
+       kq_index_t start_index, end_index, i;
+       struct knote *kn;
+       int nevents = 0;
+       int error = 0;
+
+       /*
+        * Based on the mode of the kqueue and the bound QoS of the servicer,
+        * determine the range of thread requests that need checking
+        */
+       if (kq->kq_state & KQ_WORKQ) {
+               if (flags & KEVENT_FLAG_WORKQ_MANAGER) {
+                       start_index = KQWQ_QOS_MANAGER;
+               } else if (ut->uu_kqueue_bound != kq) {
+                       return EJUSTRETURN;
+               } else {
+                       start_index = ut->uu_kqueue_qos_index;
+               }
+
+               /* manager services every request in a workq kqueue */
+               assert(start_index > 0 && start_index <= KQWQ_QOS_MANAGER);
+               end_index = (start_index == KQWQ_QOS_MANAGER) ? 0 : start_index;
+
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               if (ut->uu_kqueue_bound != kq)
+                       return EJUSTRETURN;
+
+               /*
+                * Single request servicing
+                * we want to deliver all events, regardless of the QOS
+                */
+               start_index = end_index = THREAD_QOS_UNSPECIFIED;
+       } else {
+               start_index = end_index = QOS_INDEX_KQFILE;
+       }
+       
+       i = start_index;
+
+       do {
+               if (kqueue_begin_processing(kq, i, flags) == -1) {
+                       *countp = 0;
+                       /* Nothing to process */
+                       continue;
+               }
+
+               /*
+                * loop through the enqueued knotes associated with this request,
+                * processing each one. Each request may have several queues
+                * of knotes to process (depending on the type of kqueue) so we
+                * have to loop through all the queues as long as we have additional
+                * space.
+                */
+               error = 0;
+
+               struct kqtailq *base_queue = kqueue_get_base_queue(kq, i);
+               struct kqtailq *queue = kqueue_get_high_queue(kq, i);
+               do {
+                       while (error == 0 && (kn = TAILQ_FIRST(queue)) != NULL) {
+                               error = knote_process(kn, callback, callback_data, process_data, p);
+                               if (error == EJUSTRETURN) {
+                                       error = 0;
+                               } else {
+                                       nevents++;
+                               }
+                               /* error is EWOULDBLOCK when the out event array is full */
+                       }
+               } while (error == 0 && queue-- > base_queue);
+
+               if ((kq->kq_state & KQ_WORKQ) == 0) {
+                       kqueue_end_processing(kq, i, nevents, flags);
+               }
+
+               if (error == EWOULDBLOCK) {
+                       /* break out if no more space for additional events */
+                       error = 0;
+                       break;
+               }
+       } while (i-- > end_index);
+
+       *countp = nevents;
+       return (error);
+}
+
+static void
+kqueue_scan_continue(void *data, wait_result_t wait_result)
+{
+       thread_t self = current_thread();
+       uthread_t ut = (uthread_t)get_bsdthread_info(self);
+       struct _kqueue_scan * cont_args = &ut->uu_kevent.ss_kqueue_scan;
+       struct kqueue *kq = (struct kqueue *)data;
+       struct filt_process_s *process_data = cont_args->process_data;
+       int error;
+       int count;
+
+       /* convert the (previous) wait_result to a proper error */
+       switch (wait_result) {
+       case THREAD_AWAKENED: {
+               kqlock(kq);
+       retry:
+               error = kqueue_process(kq, cont_args->call, cont_args->data, 
+                                      process_data, &count, current_proc());
+               if (error == 0 && count == 0) {
+                       if (kq->kq_state & KQ_DRAIN) {
+                               kqunlock(kq);
+                               goto drain;
+                       }
+
+                       if (kq->kq_state & KQ_WAKEUP)
+                               goto retry;
+
+                       waitq_assert_wait64((struct waitq *)&kq->kq_wqs,
+                                           KQ_EVENT, THREAD_ABORTSAFE,
+                                           cont_args->deadline);
+                       kq->kq_state |= KQ_SLEEP;
+                       kqunlock(kq);
+                       thread_block_parameter(kqueue_scan_continue, kq);
+                       /* NOTREACHED */
+               }
+               kqunlock(kq);
+               } break;
+       case THREAD_TIMED_OUT:
+               error = EWOULDBLOCK;
+               break;
+       case THREAD_INTERRUPTED:
+               error = EINTR;
+               break;
+       case THREAD_RESTART:
+       drain:
+               error = EBADF;
+               break;
+       default:
+               panic("%s: - invalid wait_result (%d)", __func__,
+                   wait_result);
+               error = 0;
+       }
+
+       /* call the continuation with the results */
+       assert(cont_args->cont != NULL);
+       (cont_args->cont)(kq, cont_args->data, error);
+}
+
+
+/*
+ * kqueue_scan - scan and wait for events in a kqueue
+ *
+ *     Process the triggered events in a kqueue.
+ *
+ *     If there are no events triggered arrange to
+ *     wait for them. If the caller provided a
+ *     continuation routine, then kevent_scan will
+ *     also.
+ *
+ *     The callback routine must be valid.
+ *     The caller must hold a use-count reference on the kq.
+ */
+
+int
+kqueue_scan(struct kqueue *kq,
+           kevent_callback_t callback,
+           kqueue_continue_t continuation,
+           void *callback_data,
+           struct filt_process_s *process_data,
+           struct timeval *atvp,
+           struct proc *p)
+{
+       thread_continue_t cont = THREAD_CONTINUE_NULL;
+       unsigned int flags;
+       uint64_t deadline;
+       int error;
+       int first;
+       int fd;
+
+       assert(callback != NULL);
+
+       /*
+        * Determine which QoS index we are servicing
+        */
+       flags = (process_data) ? process_data->fp_flags : 0;
+       fd = (process_data) ? process_data->fp_fd : -1;
+
+       first = 1;
+       for (;;) {
+               wait_result_t wait_result;
+               int count;
+
+               /*
+                * Make a pass through the kq to find events already
+                * triggered.
+                */
+               kqlock(kq);
+               error = kqueue_process(kq, callback, callback_data,
+                                      process_data, &count, p);
+               if (error || count)
+                       break; /* lock still held */
+
+               /* looks like we have to consider blocking */
+               if (first) {
+                       first = 0;
+                       /* convert the timeout to a deadline once */
+                       if (atvp->tv_sec || atvp->tv_usec) {
+                               uint64_t now;
+
+                               clock_get_uptime(&now);
+                               nanoseconds_to_absolutetime((uint64_t)atvp->tv_sec * NSEC_PER_SEC +
+                                                           atvp->tv_usec * (long)NSEC_PER_USEC,
+                                                           &deadline);
+                               if (now >= deadline) {
+                                       /* non-blocking call */
+                                       error = EWOULDBLOCK;
+                                       break; /* lock still held */
+                               }
+                               deadline -= now;
+                               clock_absolutetime_interval_to_deadline(deadline, &deadline);
+                       } else {
+                               deadline = 0;   /* block forever */
+                       }
+
+                       if (continuation) {
+                               uthread_t ut = (uthread_t)get_bsdthread_info(current_thread());
                                struct _kqueue_scan *cont_args = &ut->uu_kevent.ss_kqueue_scan;
-                               
+
                                cont_args->call = callback;
                                cont_args->cont = continuation;
                                cont_args->deadline = deadline;
-                               cont_args->data = data;
+                               cont_args->data = callback_data;
+                               cont_args->process_data = process_data;
                                cont = kqueue_scan_continue;
                        }
                }
 
-               /* go ahead and wait */
-               wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, KQ_EVENT, THREAD_ABORTSAFE, deadline);
-               kq->kq_state |= KQ_SLEEP;
-               kqunlock(kq);
-               wait_result = thread_block_parameter(cont, kq);
-               /* NOTREACHED if (continuation != NULL) */
+               if (kq->kq_state & KQ_DRAIN) {
+                       kqunlock(kq);
+                       return EBADF;
+               }
+
+               /* If awakened during processing, try again */
+               if (kq->kq_state & KQ_WAKEUP) {
+                       kqunlock(kq);
+                       continue;
+               }
+
+               /* go ahead and wait */
+               waitq_assert_wait64_leeway((struct waitq *)&kq->kq_wqs,
+                                          KQ_EVENT, THREAD_ABORTSAFE,
+                                          TIMEOUT_URGENCY_USER_NORMAL,
+                                          deadline, TIMEOUT_NO_LEEWAY);
+               kq->kq_state |= KQ_SLEEP;
+               kqunlock(kq);
+               wait_result = thread_block_parameter(cont, kq);
+               /* NOTREACHED if (continuation != NULL) */
+
+               switch (wait_result) {
+               case THREAD_AWAKENED:
+                       continue;
+               case THREAD_TIMED_OUT:
+                       return EWOULDBLOCK;
+               case THREAD_INTERRUPTED:
+                       return EINTR;
+               case THREAD_RESTART:
+                       return EBADF;
+               default:
+                       panic("%s: - bad wait_result (%d)", __func__,
+                           wait_result);
+                       error = 0;
+               }
+       }
+       kqunlock(kq);
+       return (error);
+}
+
+
+/*
+ * XXX
+ * This could be expanded to call kqueue_scan, if desired.
+ */
+/*ARGSUSED*/
+static int
+kqueue_read(__unused struct fileproc *fp,
+    __unused struct uio *uio,
+    __unused int flags,
+    __unused vfs_context_t ctx)
+{
+       return (ENXIO);
+}
+
+/*ARGSUSED*/
+static int
+kqueue_write(__unused struct fileproc *fp,
+    __unused struct uio *uio,
+    __unused int flags,
+    __unused vfs_context_t ctx)
+{
+       return (ENXIO);
+}
+
+/*ARGSUSED*/
+static int
+kqueue_ioctl(__unused struct fileproc *fp,
+    __unused u_long com,
+    __unused caddr_t data,
+    __unused vfs_context_t ctx)
+{
+       return (ENOTTY);
+}
+
+/*ARGSUSED*/
+static int
+kqueue_select(struct fileproc *fp, int which, void *wq_link_id,
+    __unused vfs_context_t ctx)
+{
+       struct kqueue *kq = (struct kqueue *)fp->f_data;
+       struct kqtailq *queue;
+       struct kqtailq *suppressq;
+       struct knote *kn;
+       int retnum = 0;
+
+       if (which != FREAD)
+               return (0);
+
+       kqlock(kq);
+
+       assert((kq->kq_state & KQ_WORKQ) == 0);
+
+       /*
+        * If this is the first pass, link the wait queue associated with the
+        * the kqueue onto the wait queue set for the select().  Normally we
+        * use selrecord() for this, but it uses the wait queue within the
+        * selinfo structure and we need to use the main one for the kqueue to
+        * catch events from KN_STAYQUEUED sources. So we do the linkage manually.
+        * (The select() call will unlink them when it ends).
+        */
+       if (wq_link_id != NULL) {
+               thread_t cur_act = current_thread();
+               struct uthread * ut = get_bsdthread_info(cur_act);
+
+               kq->kq_state |= KQ_SEL;
+               waitq_link((struct waitq *)&kq->kq_wqs, ut->uu_wqset,
+                          WAITQ_SHOULD_LOCK, (uint64_t *)wq_link_id);
+
+               /* always consume the reserved link object */
+               waitq_link_release(*(uint64_t *)wq_link_id);
+               *(uint64_t *)wq_link_id = 0;
+
+               /*
+                * selprocess() is expecting that we send it back the waitq
+                * that was just added to the thread's waitq set. In order
+                * to not change the selrecord() API (which is exported to
+                * kexts), we pass this value back through the
+                * void *wq_link_id pointer we were passed. We need to use
+                * memcpy here because the pointer may not be properly aligned
+                * on 32-bit systems.
+                */
+               void *wqptr = &kq->kq_wqs;
+               memcpy(wq_link_id, (void *)&wqptr, sizeof(void *));
+       }
+
+       if (kqueue_begin_processing(kq, QOS_INDEX_KQFILE, 0) == -1) {
+               kqunlock(kq);
+               return (0);
+       }
+
+       queue = kqueue_get_base_queue(kq, QOS_INDEX_KQFILE);
+       if (!TAILQ_EMPTY(queue)) {
+               /*
+                * there is something queued - but it might be a
+                * KN_STAYACTIVE knote, which may or may not have
+                * any events pending.  Otherwise, we have to walk
+                * the list of knotes to see, and peek at the
+                * (non-vanished) stay-active ones to be really sure.
+                */
+               while ((kn = (struct knote *)TAILQ_FIRST(queue)) != NULL) {
+                       if (kn->kn_status & KN_ACTIVE) {
+                               retnum = 1;
+                               goto out;
+                       }
+                       assert(kn->kn_status & KN_STAYACTIVE);
+                       knote_suppress(kn);
+               }
+
+               /*
+                * There were no regular events on the queue, so take
+                * a deeper look at the stay-queued ones we suppressed.
+                */
+               suppressq = kqueue_get_suppressed_queue(kq, QOS_INDEX_KQFILE);
+               while ((kn = (struct knote *)TAILQ_FIRST(suppressq)) != NULL) {
+                       unsigned peek = 1;
+
+                       assert(!knoteuse_needs_boost(kn, NULL));
+
+                       /* If didn't vanish while suppressed - peek at it */
+                       if (kqlock2knoteuse(kq, kn, KNUSE_NONE)) {
+                               peek = knote_fops(kn)->f_peek(kn);
+
+                               /* if it dropped while getting lock - move on */
+                               if (!knoteuse2kqlock(kq, kn, KNUSE_NONE))
+                                       continue;
+                       }
+
+                       /* unsuppress it */
+                       knote_unsuppress(kn);
+
+                       /* has data or it has to report a vanish */
+                       if (peek > 0) {
+                               retnum = 1;
+                               goto out;
+                       }
+               }
+       }
+
+out:
+       kqueue_end_processing(kq, QOS_INDEX_KQFILE, retnum, 0);
+       kqunlock(kq);
+       return (retnum);
+}
+
+/*
+ * kqueue_close -
+ */
+/*ARGSUSED*/
+static int
+kqueue_close(struct fileglob *fg, __unused vfs_context_t ctx)
+{
+       struct kqfile *kqf = (struct kqfile *)fg->fg_data;
+
+       assert((kqf->kqf_state & KQ_WORKQ) == 0);
+       kqueue_dealloc(&kqf->kqf_kqueue);
+       fg->fg_data = NULL;
+       return (0);
+}
+
+/*ARGSUSED*/
+/*
+ * The callers has taken a use-count reference on this kqueue and will donate it
+ * to the kqueue we are being added to.  This keeps the kqueue from closing until
+ * that relationship is torn down.
+ */
+static int
+kqueue_kqfilter(__unused struct fileproc *fp, struct knote *kn,
+               __unused struct kevent_internal_s *kev, __unused vfs_context_t ctx)
+{
+       struct kqfile *kqf = (struct kqfile *)kn->kn_fp->f_data;
+       struct kqueue *kq = &kqf->kqf_kqueue;
+       struct kqueue *parentkq = knote_get_kq(kn);
+
+       assert((kqf->kqf_state & KQ_WORKQ) == 0);
+
+       if (parentkq == kq ||
+           kn->kn_filter != EVFILT_READ) {
+               kn->kn_flags = EV_ERROR;
+               kn->kn_data = EINVAL;
+               return 0;
+       }
+
+       /*
+        * We have to avoid creating a cycle when nesting kqueues
+        * inside another.  Rather than trying to walk the whole
+        * potential DAG of nested kqueues, we just use a simple
+        * ceiling protocol.  When a kqueue is inserted into another,
+        * we check that the (future) parent is not already nested
+        * into another kqueue at a lower level than the potenial
+        * child (because it could indicate a cycle).  If that test
+        * passes, we just mark the nesting levels accordingly.
+        */
+
+       kqlock(parentkq);
+       if (parentkq->kq_level > 0 &&
+           parentkq->kq_level < kq->kq_level)
+       {
+               kqunlock(parentkq);
+               kn->kn_flags = EV_ERROR;
+               kn->kn_data = EINVAL;
+               return 0;
+       } else {
+               /* set parent level appropriately */
+               if (parentkq->kq_level == 0)
+                       parentkq->kq_level = 2;
+               if (parentkq->kq_level < kq->kq_level + 1)
+                       parentkq->kq_level = kq->kq_level + 1;
+               kqunlock(parentkq);
+
+               kn->kn_filtid = EVFILTID_KQREAD;
+               kqlock(kq);
+               KNOTE_ATTACH(&kqf->kqf_sel.si_note, kn);
+               /* indicate nesting in child, if needed */
+               if (kq->kq_level == 0)
+                       kq->kq_level = 1;
+
+               int count = kq->kq_count;
+               kqunlock(kq);
+               return (count > 0);
+       }
+}
+
+/*
+ * kqueue_drain - called when kq is closed
+ */
+/*ARGSUSED*/
+static int
+kqueue_drain(struct fileproc *fp, __unused vfs_context_t ctx)
+{
+       struct kqueue *kq = (struct kqueue *)fp->f_fglob->fg_data;
+
+       assert((kq->kq_state & KQ_WORKQ) == 0);
+
+       kqlock(kq);
+       kq->kq_state |= KQ_DRAIN;
+       kqueue_interrupt(kq);
+       kqunlock(kq);
+       return (0);
+}
+
+/*ARGSUSED*/
+int
+kqueue_stat(struct kqueue *kq, void *ub, int isstat64, proc_t p)
+{
+       assert((kq->kq_state & KQ_WORKQ) == 0);
+
+       kqlock(kq);
+       if (isstat64 != 0) {
+               struct stat64 *sb64 = (struct stat64 *)ub;
+
+               bzero((void *)sb64, sizeof(*sb64));
+               sb64->st_size = kq->kq_count;
+               if (kq->kq_state & KQ_KEV_QOS)
+                       sb64->st_blksize = sizeof(struct kevent_qos_s);
+               else if (kq->kq_state & KQ_KEV64)
+                       sb64->st_blksize = sizeof(struct kevent64_s);
+               else if (IS_64BIT_PROCESS(p))
+                       sb64->st_blksize = sizeof(struct user64_kevent);
+               else
+                       sb64->st_blksize = sizeof(struct user32_kevent);
+               sb64->st_mode = S_IFIFO;
+       } else {
+               struct stat *sb = (struct stat *)ub;
+
+               bzero((void *)sb, sizeof(*sb));
+               sb->st_size = kq->kq_count;
+               if (kq->kq_state & KQ_KEV_QOS)
+                       sb->st_blksize = sizeof(struct kevent_qos_s);
+               else if (kq->kq_state & KQ_KEV64)
+                       sb->st_blksize = sizeof(struct kevent64_s);
+               else if (IS_64BIT_PROCESS(p))
+                       sb->st_blksize = sizeof(struct user64_kevent);
+               else
+                       sb->st_blksize = sizeof(struct user32_kevent);
+               sb->st_mode = S_IFIFO;
+       }
+       kqunlock(kq);
+       return (0);
+}
+
+/*
+ * Interact with the pthread kext to request a servicing there.
+ * Eventually, this will request threads at specific QoS levels.
+ * For now, it only requests a dispatch-manager-QoS thread, and
+ * only one-at-a-time.
+ *
+ * - Caller holds the workq request lock
+ *
+ * - May be called with the kqueue's wait queue set locked,
+ *   so cannot do anything that could recurse on that.
+ */
+static void
+kqworkq_request_thread(
+       struct kqworkq *kqwq, 
+       kq_index_t qos_index)
+{
+       struct kqrequest *kqr;
+
+       assert(kqwq->kqwq_state & KQ_WORKQ);
+       assert(qos_index < KQWQ_NQOS);
+
+       kqr = kqworkq_get_request(kqwq, qos_index);
+
+       assert(kqr->kqr_state & KQR_WAKEUP);
+
+       /* 
+        * If we have already requested a thread, and it hasn't
+        * started processing yet, there's no use hammering away
+        * on the pthread kext.
+        */
+       if (kqr->kqr_state & KQR_THREQUESTED)
+               return;
+
+       assert((kqr->kqr_state & KQR_BOUND) == 0);
+
+       /* request additional workq threads if appropriate */
+       if (pthread_functions != NULL &&
+           pthread_functions->workq_reqthreads != NULL) {
+               unsigned int flags = KEVENT_FLAG_WORKQ;
+               unsigned long priority;
+               thread_t wqthread;
+
+               /* Compute the appropriate pthread priority */
+               priority = qos_from_qos_index(qos_index);
+
+#if 0
+               /* JMM - for now remain compatible with old invocations */
+               /* set the over-commit flag on the request if needed */
+               if (kqr->kqr_state & KQR_THOVERCOMMIT)
+                       priority |= _PTHREAD_PRIORITY_OVERCOMMIT_FLAG;
+#endif /* 0 */
+
+               /* Compute a priority based on qos_index. */
+               struct workq_reqthreads_req_s request = {
+                       .priority = priority,
+                       .count = 1
+               };
+
+               /* mark that we are making a request */
+               kqr->kqr_state |= KQR_THREQUESTED;
+               if (qos_index == KQWQ_QOS_MANAGER)
+                       kqr->kqr_state |= KQWQ_THMANAGER;
+
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_THREQUEST),
+                             0, qos_index,
+                             (((uintptr_t)kqr->kqr_override_index << 8) |
+                              (uintptr_t)kqr->kqr_state));
+               wqthread = (*pthread_functions->workq_reqthreads)(kqwq->kqwq_p, 1, &request);
+
+               /* We've been switched to the emergency/manager thread */
+               if (wqthread == (thread_t)-1) {
+                       assert(qos_index != KQWQ_QOS_MANAGER);
+                       kqr->kqr_state |= KQWQ_THMANAGER;
+                       return;
+               }
+
+               /*
+                * bind the returned thread identity
+                * This goes away when we switch to synchronous callback
+                * binding from the pthread kext.
+                */
+               if (wqthread != NULL) {
+                       kqworkq_bind_thread_impl(kqwq, qos_index, wqthread, flags);
+               }
+       }
+}
+
+/*
+ * If we aren't already busy processing events [for this QoS],
+ * request workq thread support as appropriate.
+ *
+ * TBD - for now, we don't segregate out processing by QoS.
+ *
+ * - May be called with the kqueue's wait queue set locked,
+ *   so cannot do anything that could recurse on that.
+ */
+static void
+kqworkq_request_help(
+       struct kqworkq *kqwq, 
+       kq_index_t qos_index)
+{
+       struct kqrequest *kqr;
+
+       /* convert to thread qos value */
+       assert(qos_index < KQWQ_NQOS);
+       
+       kqwq_req_lock(kqwq);
+       kqr = kqworkq_get_request(kqwq, qos_index);
+
+       if ((kqr->kqr_state & KQR_WAKEUP) == 0) {
+               /* Indicate that we needed help from this request */
+               kqr->kqr_state |= KQR_WAKEUP;
+
+               /* Go assure a thread request has been made */
+               kqworkq_request_thread(kqwq, qos_index);
+       }
+       kqwq_req_unlock(kqwq);
+}
+
+static void
+kqworkloop_threadreq_impl(struct kqworkloop *kqwl, kq_index_t qos_index)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       unsigned long pri = pthread_priority_for_kqrequest(kqr, qos_index);
+       int op, ret;
+
+       assert((kqr->kqr_state & (KQR_THREQUESTED | KQR_BOUND)) == KQR_THREQUESTED);
+
+       /*
+        * New-style thread request supported. Provide
+        * the pthread kext a pointer to a workq_threadreq_s
+        * structure for its use until a corresponding
+        * workloop_fulfill_threqreq callback.
+        */
+       if (current_proc() == kqwl->kqwl_kqueue.kq_p) {
+               op = WORKQ_THREADREQ_WORKLOOP_NO_THREAD_CALL;
+       } else {
+               op = WORKQ_THREADREQ_WORKLOOP;
+       }
+again:
+       ret = (*pthread_functions->workq_threadreq)(kqwl->kqwl_p, &kqr->kqr_req,
+                       WORKQ_THREADREQ_WORKLOOP, pri, 0);
+       switch (ret) {
+       case ENOTSUP:
+               assert(op == WORKQ_THREADREQ_WORKLOOP_NO_THREAD_CALL);
+               op = WORKQ_THREADREQ_WORKLOOP;
+               goto again;
+
+       case ECANCELED:
+       case EINVAL:
+               /*
+                * Process is shutting down or exec'ing.
+                * All the kqueues are going to be cleaned up
+                * soon. Forget we even asked for a thread -
+                * and make sure we don't ask for more.
+                */
+               kqueue_release((struct kqueue *)kqwl, KQUEUE_CANT_BE_LAST_REF);
+               kqr->kqr_state &= ~KQR_THREQUESTED;
+               kqr->kqr_state |= KQR_DRAIN;
+               break;
+
+       case EAGAIN:
+               assert(op == WORKQ_THREADREQ_WORKLOOP_NO_THREAD_CALL);
+               act_set_astkevent(current_thread(), AST_KEVENT_REDRIVE_THREADREQ);
+               break;
+
+       default:
+               assert(ret == 0);
+       }
+}
+
+static void
+kqworkloop_threadreq_modify(struct kqworkloop *kqwl, kq_index_t qos_index)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       unsigned long pri = pthread_priority_for_kqrequest(kqr, qos_index);
+       int ret, op = WORKQ_THREADREQ_CHANGE_PRI_NO_THREAD_CALL;
+
+       assert((kqr->kqr_state & (KQR_THREQUESTED | KQR_BOUND)) == KQR_THREQUESTED);
+
+       if (current_proc() == kqwl->kqwl_kqueue.kq_p) {
+               op = WORKQ_THREADREQ_CHANGE_PRI_NO_THREAD_CALL;
+       } else {
+               op = WORKQ_THREADREQ_CHANGE_PRI;
+       }
+again:
+       ret = (*pthread_functions->workq_threadreq_modify)(kqwl->kqwl_p,
+                       &kqr->kqr_req, op, pri, 0);
+       switch (ret) {
+       case ENOTSUP:
+               assert(op == WORKQ_THREADREQ_CHANGE_PRI_NO_THREAD_CALL);
+               op = WORKQ_THREADREQ_CHANGE_PRI;
+               goto again;
+
+       case EAGAIN:
+               assert(op == WORKQ_THREADREQ_WORKLOOP_NO_THREAD_CALL);
+               act_set_astkevent(current_thread(), AST_KEVENT_REDRIVE_THREADREQ);
+               break;
+
+       case ECANCELED:
+       case EINVAL:
+       case 0:
+               break;
+
+       default:
+               assert(ret == 0);
+       }
+}
+
+/*
+ * Interact with the pthread kext to request a servicing thread.
+ * This will request a single thread at the highest QoS level
+ * for which there is work (whether that was the requested QoS
+ * for an event or an override applied to a lower-QoS request).
+ *
+ * - Caller holds the workloop request lock
+ *
+ * - May be called with the kqueue's wait queue set locked,
+ *   so cannot do anything that could recurse on that.
+ */
+static void
+kqworkloop_request_thread(struct kqworkloop *kqwl, kq_index_t qos_index)
+{
+       struct kqrequest *kqr;
+
+       assert(kqwl->kqwl_state & KQ_WORKLOOP);
+
+       kqr = &kqwl->kqwl_request;
+
+       assert(kqwl->kqwl_owner == THREAD_NULL);
+       assert((kqr->kqr_state & KQR_BOUND) == 0);
+       assert((kqr->kqr_state & KQR_THREQUESTED) == 0);
+       assert(!(kqwl->kqwl_kqueue.kq_state & KQ_NO_WQ_THREAD));
+
+       /* If we're draining thread requests, just bail */
+       if (kqr->kqr_state & KQR_DRAIN)
+               return;
+
+       if (pthread_functions != NULL &&
+                       pthread_functions->workq_threadreq != NULL) {
+               /*
+                * set request state flags, etc... before calling pthread
+                * This assures they are set before a possible synchronous
+                * callback to workloop_fulfill_threadreq().
+                */
+               kqr->kqr_state |= KQR_THREQUESTED;
+
+               /* Add a thread request reference on the kqueue. */
+               kqueue_retain((struct kqueue *)kqwl);
+
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_THREQUEST),
+                             kqwl->kqwl_dynamicid,
+                             0, qos_index, kqr->kqr_state);
+               kqworkloop_threadreq_impl(kqwl, qos_index);
+       } else {
+               panic("kqworkloop_request_thread");
+               return;
+       }
+}
+
+static void
+kqworkloop_update_sync_override_state(struct kqworkloop *kqwl, boolean_t sync_ipc_override)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       kqwl_req_lock(kqwl);
+       kqr->kqr_has_sync_override = sync_ipc_override;
+       kqwl_req_unlock(kqwl);
+
+}
+
+static inline kq_index_t
+kqworkloop_combined_qos(struct kqworkloop *kqwl, boolean_t *ipc_override_is_sync)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       kq_index_t override;
+
+       *ipc_override_is_sync = FALSE;
+       override = MAX(MAX(kqr->kqr_qos_index, kqr->kqr_override_index),
+                                       kqr->kqr_dsync_waiters_qos);
+
+       if (kqr->kqr_sync_suppress_count > 0 || kqr->kqr_has_sync_override) {
+               *ipc_override_is_sync = TRUE;
+               override = THREAD_QOS_USER_INTERACTIVE;
+       }
+       return override;
+}
+
+static inline void
+kqworkloop_request_fire_r2k_notification(struct kqworkloop *kqwl)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+
+       kqwl_req_held(kqwl);
+
+       if (kqr->kqr_state & KQR_R2K_NOTIF_ARMED) {
+               assert(kqr->kqr_state & KQR_BOUND);
+               assert(kqr->kqr_thread);
+
+               kqr->kqr_state &= ~KQR_R2K_NOTIF_ARMED;
+               act_set_astkevent(kqr->kqr_thread, AST_KEVENT_RETURN_TO_KERNEL);
+       }
+}
+
+static void
+kqworkloop_update_threads_qos(struct kqworkloop *kqwl, int op, kq_index_t qos)
+{
+       const uint8_t KQWL_STAYACTIVE_FIRED_BIT = (1 << 0);
+
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       boolean_t old_ipc_override_is_sync = FALSE;
+       kq_index_t old_qos = kqworkloop_combined_qos(kqwl, &old_ipc_override_is_sync);
+       struct kqueue *kq = &kqwl->kqwl_kqueue;
+       bool static_thread = (kq->kq_state & KQ_NO_WQ_THREAD);
+       kq_index_t i;
+
+       /* must hold the kqr lock */
+       kqwl_req_held(kqwl);
+
+       switch (op) {
+       case KQWL_UTQ_UPDATE_WAKEUP_QOS:
+               if (qos == KQWL_BUCKET_STAYACTIVE) {
+                       /*
+                        * the KQWL_BUCKET_STAYACTIVE is not a QoS bucket, we only remember
+                        * a high watermark (kqr_stayactive_qos) of any stay active knote
+                        * that was ever registered with this workloop.
+                        *
+                        * When waitq_set__CALLING_PREPOST_HOOK__() wakes up any stay active
+                        * knote, we use this high-watermark as a wakeup-index, and also set
+                        * the magic KQWL_BUCKET_STAYACTIVE bit to make sure we remember
+                        * there is at least one stay active knote fired until the next full
+                        * processing of this bucket.
+                        */
+                       kqr->kqr_wakeup_indexes |= KQWL_STAYACTIVE_FIRED_BIT;
+                       qos = kqr->kqr_stayactive_qos;
+                       assert(qos);
+                       assert(!static_thread);
+               }
+               if (kqr->kqr_wakeup_indexes & (1 << qos)) {
+                       assert(kqr->kqr_state & KQR_WAKEUP);
+                       break;
+               }
+
+               kqr->kqr_wakeup_indexes |= (1 << qos);
+               kqr->kqr_state |= KQR_WAKEUP;
+               kqworkloop_request_fire_r2k_notification(kqwl);
+               goto recompute_async;
+
+       case KQWL_UTQ_UPDATE_STAYACTIVE_QOS:
+               assert(qos);
+               if (kqr->kqr_stayactive_qos < qos) {
+                       kqr->kqr_stayactive_qos = qos;
+                       if (kqr->kqr_wakeup_indexes & KQWL_STAYACTIVE_FIRED_BIT) {
+                               assert(kqr->kqr_state & KQR_WAKEUP);
+                               kqr->kqr_wakeup_indexes |= (1 << qos);
+                               goto recompute_async;
+                       }
+               }
+               break;
+
+       case KQWL_UTQ_RECOMPUTE_WAKEUP_QOS:
+               kqlock_held(kq); // to look at kq_queues
+               kqr->kqr_has_sync_override = FALSE;
+               i = KQWL_BUCKET_STAYACTIVE;
+               if (TAILQ_EMPTY(&kqr->kqr_suppressed)) {
+                       kqr->kqr_override_index = THREAD_QOS_UNSPECIFIED;
+               }
+               if (!TAILQ_EMPTY(&kq->kq_queue[i]) &&
+                               (kqr->kqr_wakeup_indexes & KQWL_STAYACTIVE_FIRED_BIT)) {
+                       /*
+                        * If the KQWL_STAYACTIVE_FIRED_BIT is set, it means a stay active
+                        * knote may have fired, so we need to merge in kqr_stayactive_qos.
+                        *
+                        * Unlike other buckets, this one is never empty but could be idle.
+                        */
+                       kqr->kqr_wakeup_indexes &= KQWL_STAYACTIVE_FIRED_BIT;
+                       kqr->kqr_wakeup_indexes |= (1 << kqr->kqr_stayactive_qos);
+               } else {
+                       kqr->kqr_wakeup_indexes = 0;
+               }
+               for (i = THREAD_QOS_UNSPECIFIED + 1; i < KQWL_BUCKET_STAYACTIVE; i++) {
+                       if (!TAILQ_EMPTY(&kq->kq_queue[i])) {
+                               kqr->kqr_wakeup_indexes |= (1 << i);
+                               struct knote *kn = TAILQ_FIRST(&kqwl->kqwl_kqueue.kq_queue[i]);
+                               if (i == THREAD_QOS_USER_INTERACTIVE &&
+                                   kn->kn_qos_override_is_sync) {
+                                       kqr->kqr_has_sync_override = TRUE;
+                               }
+                       }
+               }
+               if (kqr->kqr_wakeup_indexes) {
+                       kqr->kqr_state |= KQR_WAKEUP;
+                       kqworkloop_request_fire_r2k_notification(kqwl);
+               } else {
+                       kqr->kqr_state &= ~KQR_WAKEUP;
+               }
+               assert(qos == THREAD_QOS_UNSPECIFIED);
+               goto recompute_async;
+
+       case KQWL_UTQ_RESET_WAKEUP_OVERRIDE:
+               kqr->kqr_override_index = THREAD_QOS_UNSPECIFIED;
+               assert(qos == THREAD_QOS_UNSPECIFIED);
+               goto recompute_async;
+
+       case KQWL_UTQ_UPDATE_WAKEUP_OVERRIDE:
+       recompute_async:
+               /*
+                * When modifying the wakeup QoS or the async override QoS, we always
+                * need to maintain our invariant that kqr_override_index is at least as
+                * large as the highest QoS for which an event is fired.
+                *
+                * However this override index can be larger when there is an overriden
+                * suppressed knote pushing on the kqueue.
+                */
+               if (kqr->kqr_wakeup_indexes > (1 << qos)) {
+                       qos = fls(kqr->kqr_wakeup_indexes) - 1; /* fls is 1-based */
+               }
+               if (kqr->kqr_override_index < qos) {
+                       kqr->kqr_override_index = qos;
+               }
+               break;
+
+       case KQWL_UTQ_REDRIVE_EVENTS:
+               break;
+
+       case KQWL_UTQ_SET_ASYNC_QOS:
+               filt_wlheld(kqwl);
+               kqr->kqr_qos_index = qos;
+               break;
+
+       case KQWL_UTQ_SET_SYNC_WAITERS_QOS:
+               filt_wlheld(kqwl);
+               kqr->kqr_dsync_waiters_qos = qos;
+               break;
+
+       default:
+               panic("unknown kqwl thread qos update operation: %d", op);
+       }
+
+       boolean_t new_ipc_override_is_sync = FALSE;
+       kq_index_t new_qos = kqworkloop_combined_qos(kqwl, &new_ipc_override_is_sync);
+       thread_t kqwl_owner = kqwl->kqwl_owner;
+       thread_t servicer = kqr->kqr_thread;
+       __assert_only int ret;
+
+       /*
+        * Apply the diffs to the owner if applicable
+        */
+       if (filt_wlowner_is_valid(kqwl_owner)) {
+#if 0
+               /* JMM - need new trace hooks for owner overrides */
+               KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_THADJUST),
+                               kqwl->kqwl_dynamicid,
+                               (kqr->kqr_state & KQR_BOUND) ? thread_tid(kqwl_owner) : 0,
+                               (kqr->kqr_qos_index << 8) | new_qos,
+                               (kqr->kqr_override_index << 8) | kqr->kqr_state);
+#endif
+               if (new_qos == kqr->kqr_dsync_owner_qos) {
+                       // nothing to do
+               } else if (kqr->kqr_dsync_owner_qos == THREAD_QOS_UNSPECIFIED) {
+                       thread_add_ipc_override(kqwl_owner, new_qos);
+               } else if (new_qos == THREAD_QOS_UNSPECIFIED) {
+                       thread_drop_ipc_override(kqwl_owner);
+               } else /* kqr->kqr_dsync_owner_qos != new_qos */ {
+                       thread_update_ipc_override(kqwl_owner, new_qos);
+               }
+               kqr->kqr_dsync_owner_qos = new_qos;
+
+               if (new_ipc_override_is_sync &&
+                       !kqr->kqr_owner_override_is_sync) {
+                       thread_add_sync_ipc_override(kqwl_owner);
+               } else if (!new_ipc_override_is_sync &&
+                       kqr->kqr_owner_override_is_sync) {
+                       thread_drop_sync_ipc_override(kqwl_owner);
+               }
+               kqr->kqr_owner_override_is_sync = new_ipc_override_is_sync;
+       }
+
+       /*
+        * apply the diffs to the servicer
+        */
+       if (static_thread) {
+               /*
+                * Statically bound thread
+                *
+                * These threads don't participates in QoS overrides today, just wakeup
+                * the thread blocked on this kqueue if a new event arrived.
+                */
+
+               switch (op) {
+               case KQWL_UTQ_UPDATE_WAKEUP_QOS:
+               case KQWL_UTQ_UPDATE_STAYACTIVE_QOS:
+               case KQWL_UTQ_RECOMPUTE_WAKEUP_QOS:
+                       break;
+
+               case KQWL_UTQ_RESET_WAKEUP_OVERRIDE:
+               case KQWL_UTQ_UPDATE_WAKEUP_OVERRIDE:
+               case KQWL_UTQ_REDRIVE_EVENTS:
+               case KQWL_UTQ_SET_ASYNC_QOS:
+               case KQWL_UTQ_SET_SYNC_WAITERS_QOS:
+                       panic("should never be called");
+                       break;
+               }
+
+               kqlock_held(kq);
+
+               if ((kqr->kqr_state & KQR_BOUND) && (kqr->kqr_state & KQR_WAKEUP)) {
+                       assert(servicer && !is_workqueue_thread(servicer));
+                       if (kq->kq_state & (KQ_SLEEP | KQ_SEL)) {
+                               kq->kq_state &= ~(KQ_SLEEP | KQ_SEL);
+                               waitq_wakeup64_all((struct waitq *)&kq->kq_wqs, KQ_EVENT,
+                                               THREAD_AWAKENED, WAITQ_ALL_PRIORITIES);
+                       }
+               }
+       } else if ((kqr->kqr_state & KQR_THREQUESTED) == 0) {
+               /*
+                * No servicer, nor thread-request
+                *
+                * Make a new thread request, unless there is an owner (or the workloop
+                * is suspended in userland) or if there is no asynchronous work in the
+                * first place.
+                */
+
+               if (kqwl_owner == THREAD_NULL && (kqr->kqr_state & KQR_WAKEUP)) {
+                       kqworkloop_request_thread(kqwl, new_qos);
+               }
+       } else if ((kqr->kqr_state & KQR_BOUND) == 0 &&
+                       (kqwl_owner || (kqr->kqr_state & KQR_WAKEUP) == 0)) {
+               /*
+                * No servicer, thread request in flight we want to cancel
+                *
+                * We just got rid of the last knote of the kqueue or noticed an owner
+                * with a thread request still in flight, take it back.
+                */
+               ret = (*pthread_functions->workq_threadreq_modify)(kqwl->kqwl_p,
+                               &kqr->kqr_req, WORKQ_THREADREQ_CANCEL, 0, 0);
+               if (ret == 0) {
+                       kqr->kqr_state &= ~KQR_THREQUESTED;
+                       kqueue_release(kq, KQUEUE_CANT_BE_LAST_REF);
+               }
+       } else {
+               boolean_t qos_changed = FALSE;
+
+               /*
+                * Servicer or request is in flight
+                *
+                * Just apply the diff to the servicer or the thread request
+                */
+               if (kqr->kqr_state & KQR_BOUND) {
+                       servicer = kqr->kqr_thread;
+                       struct uthread *ut = get_bsdthread_info(servicer);
+                       if (ut->uu_kqueue_qos_index != new_qos) {
+                               if (ut->uu_kqueue_qos_index == THREAD_QOS_UNSPECIFIED) {
+                                       thread_add_ipc_override(servicer, new_qos);
+                               } else if (new_qos == THREAD_QOS_UNSPECIFIED) {
+                                       thread_drop_ipc_override(servicer);
+                               } else /* ut->uu_kqueue_qos_index != new_qos */ {
+                                       thread_update_ipc_override(servicer, new_qos);
+                               }
+                               ut->uu_kqueue_qos_index = new_qos;
+                               qos_changed = TRUE;
+                       }
+
+                       if (new_ipc_override_is_sync != ut->uu_kqueue_override_is_sync) {
+                               if (new_ipc_override_is_sync &&
+                                   !ut->uu_kqueue_override_is_sync) {
+                                       thread_add_sync_ipc_override(servicer);
+                               } else if (!new_ipc_override_is_sync &&
+                                       ut->uu_kqueue_override_is_sync) {
+                                       thread_drop_sync_ipc_override(servicer);
+                               }
+                               ut->uu_kqueue_override_is_sync = new_ipc_override_is_sync;
+                               qos_changed = TRUE;
+                       }
+               } else if (old_qos != new_qos) {
+                       assert(new_qos);
+                       kqworkloop_threadreq_modify(kqwl, new_qos);
+                       qos_changed = TRUE;
+               }
+               if (qos_changed) {
+                       servicer = kqr->kqr_thread;
+                       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_THADJUST),
+                               kqwl->kqwl_dynamicid,
+                               (kqr->kqr_state & KQR_BOUND) ? thread_tid(servicer) : 0,
+                               (kqr->kqr_qos_index << 16) | (new_qos << 8) | new_ipc_override_is_sync,
+                               (kqr->kqr_override_index << 8) | kqr->kqr_state);
+               }
+       }
+}
+
+static void
+kqworkloop_request_help(struct kqworkloop *kqwl, kq_index_t qos_index)
+{
+       /* convert to thread qos value */
+       assert(qos_index < KQWL_NBUCKETS);
+
+       kqwl_req_lock(kqwl);
+       kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_WAKEUP_QOS, qos_index);
+       kqwl_req_unlock(kqwl);
+}
+
+/*
+ * These arrays described the low and high qindexes for a given qos_index.
+ * The values come from the chart in <sys/eventvar.h> (must stay in sync).
+ */
+static kq_index_t _kqwq_base_index[KQWQ_NQOS] = {0, 0, 6, 11, 15, 18, 20, 21};
+static kq_index_t _kqwq_high_index[KQWQ_NQOS] = {0, 5, 10, 14, 17, 19, 20, 21};
+
+static struct kqtailq *
+kqueue_get_base_queue(struct kqueue *kq, kq_index_t qos_index)
+{
+       if (kq->kq_state & KQ_WORKQ) {
+               assert(qos_index < KQWQ_NQOS);
+               return &kq->kq_queue[_kqwq_base_index[qos_index]];
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               assert(qos_index < KQWL_NBUCKETS);
+               return &kq->kq_queue[qos_index];
+       } else {
+               assert(qos_index == QOS_INDEX_KQFILE);
+               return &kq->kq_queue[QOS_INDEX_KQFILE];
+       }
+}
+
+static struct kqtailq *
+kqueue_get_high_queue(struct kqueue *kq, kq_index_t qos_index)
+{
+       if (kq->kq_state & KQ_WORKQ) {
+               assert(qos_index < KQWQ_NQOS);
+               return &kq->kq_queue[_kqwq_high_index[qos_index]];
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               assert(qos_index < KQWL_NBUCKETS);
+               return &kq->kq_queue[KQWL_BUCKET_STAYACTIVE];
+       } else {
+               assert(qos_index == QOS_INDEX_KQFILE);
+               return &kq->kq_queue[QOS_INDEX_KQFILE];
+       }
+}
+
+static int
+kqueue_queue_empty(struct kqueue *kq, kq_index_t qos_index)
+{
+       struct kqtailq *base_queue = kqueue_get_base_queue(kq, qos_index);
+       struct kqtailq *queue = kqueue_get_high_queue(kq, qos_index);
+
+       do {
+               if (!TAILQ_EMPTY(queue))
+                       return 0;
+       } while (queue-- > base_queue);
+       return 1;
+}
+
+static struct kqtailq *
+kqueue_get_suppressed_queue(struct kqueue *kq, kq_index_t qos_index)
+{
+    struct kqtailq *res;
+       struct kqrequest *kqr;
+
+       if (kq->kq_state & KQ_WORKQ) {
+               struct kqworkq *kqwq = (struct kqworkq *)kq;
+
+               kqr = kqworkq_get_request(kqwq, qos_index);
+               res = &kqr->kqr_suppressed;
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               kqr = &kqwl->kqwl_request;
+               res = &kqr->kqr_suppressed;
+       } else {
+               struct kqfile *kqf = (struct kqfile *)kq;
+               res = &kqf->kqf_suppressed;
+       }
+       return res;
+}
+
+static kq_index_t
+knote_get_queue_index(struct knote *kn)
+{
+       kq_index_t override_index = knote_get_qos_override_index(kn);
+       kq_index_t qos_index = knote_get_qos_index(kn);
+       struct kqueue *kq = knote_get_kq(kn);
+       kq_index_t res;
+
+       if (kq->kq_state & KQ_WORKQ) {
+               res = _kqwq_base_index[qos_index];
+               if (override_index > qos_index)
+                       res += override_index - qos_index;
+               assert(res <= _kqwq_high_index[qos_index]);
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               res = MAX(override_index, qos_index);
+               assert(res < KQWL_NBUCKETS);
+       } else {
+               assert(qos_index == QOS_INDEX_KQFILE);
+               assert(override_index == QOS_INDEX_KQFILE);
+               res = QOS_INDEX_KQFILE;
+       }
+       return res;
+}
+
+static struct kqtailq *
+knote_get_queue(struct knote *kn)
+{
+       kq_index_t qindex = knote_get_queue_index(kn);
+
+       return &(knote_get_kq(kn))->kq_queue[qindex];
+}
+
+static kq_index_t
+knote_get_req_index(struct knote *kn)
+{
+       return kn->kn_req_index;
+}
+
+static kq_index_t
+knote_get_qos_index(struct knote *kn)
+{
+       return kn->kn_qos_index;
+}
+
+static void
+knote_set_qos_index(struct knote *kn, kq_index_t qos_index)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+
+       assert(qos_index < KQWQ_NQOS);
+       assert((kn->kn_status & KN_QUEUED) == 0);
+
+       if (kq->kq_state & KQ_WORKQ) {
+               assert(qos_index > THREAD_QOS_UNSPECIFIED);
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               /* XXX this policy decision shouldn't be here */
+               if (qos_index == THREAD_QOS_UNSPECIFIED)
+                       qos_index = THREAD_QOS_LEGACY;
+       } else
+               qos_index = QOS_INDEX_KQFILE;
+
+       /* always set requested */
+       kn->kn_req_index = qos_index;
+
+       /* only adjust in-use qos index when not suppressed */
+       if ((kn->kn_status & KN_SUPPRESSED) == 0)
+               kn->kn_qos_index = qos_index;
+}
+
+static void
+knote_set_qos_overcommit(struct knote *kn)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       struct kqrequest *kqr;
+
+       /* turn overcommit on for the appropriate thread request? */
+       if (kn->kn_qos & _PTHREAD_PRIORITY_OVERCOMMIT_FLAG) {
+               if (kq->kq_state & KQ_WORKQ) {
+                       kq_index_t qos_index = knote_get_qos_index(kn);
+                       struct kqworkq *kqwq = (struct kqworkq *)kq;
+
+                       kqr = kqworkq_get_request(kqwq, qos_index);
+
+                       kqwq_req_lock(kqwq);
+                       kqr->kqr_state |= KQR_THOVERCOMMIT;
+                       kqwq_req_unlock(kqwq);
+               } else if (kq->kq_state & KQ_WORKLOOP) {
+                       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+                       kqr = &kqwl->kqwl_request;
+
+                       kqwl_req_lock(kqwl);
+                       kqr->kqr_state |= KQR_THOVERCOMMIT;
+                       kqwl_req_unlock(kqwl);
+               }
+       }
+}
+
+static kq_index_t
+knote_get_qos_override_index(struct knote *kn)
+{
+       return kn->kn_qos_override;
+}
+
+static void
+knote_set_qos_override_index(struct knote *kn, kq_index_t override_index,
+               boolean_t override_is_sync)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       kq_index_t qos_index = knote_get_qos_index(kn);
+       kq_index_t old_override_index = knote_get_qos_override_index(kn);
+       boolean_t old_override_is_sync = kn->kn_qos_override_is_sync;
+       uint32_t flags = 0;
+
+       assert((kn->kn_status & KN_QUEUED) == 0);
+
+       if (override_index == KQWQ_QOS_MANAGER) {
+               assert(qos_index == KQWQ_QOS_MANAGER);
+       } else {
+               assert(override_index < KQWQ_QOS_MANAGER);
+       }
+
+       kn->kn_qos_override = override_index;
+       kn->kn_qos_override_is_sync = override_is_sync;
+
+       /*
+        * If this is a workq/workloop kqueue, apply the override to the
+        * servicing thread.
+        */
+       if (kq->kq_state & KQ_WORKQ)  {
+               struct kqworkq *kqwq = (struct kqworkq *)kq;
+
+               assert(qos_index > THREAD_QOS_UNSPECIFIED);
+               kqworkq_update_override(kqwq, qos_index, override_index);
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               if ((kn->kn_status & KN_SUPPRESSED) == KN_SUPPRESSED) {
+                       flags = flags | KQWL_UO_UPDATE_SUPPRESS_SYNC_COUNTERS;
+
+                       if (override_index == THREAD_QOS_USER_INTERACTIVE
+                                       && override_is_sync) {
+                               flags = flags | KQWL_UO_NEW_OVERRIDE_IS_SYNC_UI;
+                       }
+
+                       if (old_override_index == THREAD_QOS_USER_INTERACTIVE
+                                       && old_override_is_sync) {
+                               flags = flags | KQWL_UO_OLD_OVERRIDE_IS_SYNC_UI;
+                       }
+               }
+
+               assert(qos_index > THREAD_QOS_UNSPECIFIED);
+               kqworkloop_update_override(kqwl, qos_index, override_index, flags);
+       }
+}
+
+static kq_index_t
+knote_get_sync_qos_override_index(struct knote *kn)
+{
+       return kn->kn_qos_sync_override;
+}
+
+static void
+kqworkq_update_override(struct kqworkq *kqwq, kq_index_t qos_index, kq_index_t override_index)
+{
+       struct kqrequest *kqr;
+       kq_index_t old_override_index;
+
+       if (override_index <= qos_index) {
+               return;
+       }
+
+       kqr = kqworkq_get_request(kqwq, qos_index);
+
+       kqwq_req_lock(kqwq);
+       old_override_index = kqr->kqr_override_index;
+       if (override_index > MAX(kqr->kqr_qos_index, old_override_index)) {
+               kqr->kqr_override_index = override_index;
+
+               /* apply the override to [incoming?] servicing thread */
+               if (kqr->kqr_state & KQR_BOUND) {
+                       thread_t wqthread = kqr->kqr_thread;
+
+                       /* only apply if non-manager */
+                       assert(wqthread);
+                   if ((kqr->kqr_state & KQWQ_THMANAGER) == 0) {
+                               if (old_override_index)
+                                       thread_update_ipc_override(wqthread, override_index);
+                               else
+                                       thread_add_ipc_override(wqthread, override_index);
+                       }
+               }
+       }
+       kqwq_req_unlock(kqwq);
+}
+
+/* called with the kqworkq lock held */
+static void
+kqworkq_bind_thread_impl(
+       struct kqworkq *kqwq,
+       kq_index_t qos_index,
+       thread_t thread,
+       unsigned int flags)
+{
+       /* request lock must be held */
+       kqwq_req_held(kqwq);
+
+       struct kqrequest *kqr = kqworkq_get_request(kqwq, qos_index);
+       assert(kqr->kqr_state & KQR_THREQUESTED);
+
+       if (qos_index == KQWQ_QOS_MANAGER)
+               flags |= KEVENT_FLAG_WORKQ_MANAGER;
+
+       struct uthread *ut = get_bsdthread_info(thread);
+
+       /* 
+        * If this is a manager, and the manager request bit is
+        * not set, assure no other thread is bound. If the bit
+        * is set, make sure the old thread is us (or not set).
+        */
+       if (flags & KEVENT_FLAG_WORKQ_MANAGER) {
+               if ((kqr->kqr_state & KQR_BOUND) == 0) {
+                       kqr->kqr_state |= (KQR_BOUND | KQWQ_THMANAGER);
+                       TAILQ_INIT(&kqr->kqr_suppressed);
+                       kqr->kqr_thread = thread;
+                       ut->uu_kqueue_bound = (struct kqueue *)kqwq;
+                       ut->uu_kqueue_qos_index = KQWQ_QOS_MANAGER;
+                       ut->uu_kqueue_flags = (KEVENT_FLAG_WORKQ | 
+                                              KEVENT_FLAG_WORKQ_MANAGER);
+               } else {
+                       assert(kqr->kqr_state & KQR_BOUND);
+                       assert(thread == kqr->kqr_thread);
+                       assert(ut->uu_kqueue_bound == (struct kqueue *)kqwq);
+                       assert(ut->uu_kqueue_qos_index == KQWQ_QOS_MANAGER);
+                       assert(ut->uu_kqueue_flags & KEVENT_FLAG_WORKQ_MANAGER);
+               }
+               return;
+       }
+
+       /* Just a normal one-queue servicing thread */
+       assert(kqr->kqr_state & KQR_THREQUESTED);
+       assert(kqr->kqr_qos_index == qos_index);
+
+       if ((kqr->kqr_state & KQR_BOUND) == 0) {
+               kqr->kqr_state |= KQR_BOUND;
+               TAILQ_INIT(&kqr->kqr_suppressed);
+               kqr->kqr_thread = thread;
+
+               /* apply an ipc QoS override if one is needed */
+               if (kqr->kqr_override_index) {
+                       assert(kqr->kqr_qos_index);
+                       assert(kqr->kqr_override_index > kqr->kqr_qos_index);
+                       assert(thread_get_ipc_override(thread) == THREAD_QOS_UNSPECIFIED);
+                       thread_add_ipc_override(thread, kqr->kqr_override_index);
+               }
+
+               /* indicate that we are processing in the uthread */
+               ut->uu_kqueue_bound = (struct kqueue *)kqwq;
+               ut->uu_kqueue_qos_index = qos_index;
+               ut->uu_kqueue_flags = flags;
+       } else {
+               /*
+                * probably syncronously bound AND post-request bound
+                * this logic can go away when we get rid of post-request bind
+                */
+               assert(kqr->kqr_state & KQR_BOUND);
+               assert(thread == kqr->kqr_thread);
+               assert(ut->uu_kqueue_bound == (struct kqueue *)kqwq);
+               assert(ut->uu_kqueue_qos_index == qos_index);
+               assert((ut->uu_kqueue_flags & flags) == flags);
+       }
+}
+
+static void
+kqworkloop_update_override(
+       struct kqworkloop *kqwl,
+       kq_index_t qos_index,
+       kq_index_t override_index,
+       uint32_t flags)
+{
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+
+       kqwl_req_lock(kqwl);
+
+       /* Do not override on attached threads */
+       if (kqr->kqr_state & KQR_BOUND) {
+               assert(kqr->kqr_thread);
+
+               if (kqwl->kqwl_kqueue.kq_state & KQ_NO_WQ_THREAD) {
+                       kqwl_req_unlock(kqwl);
+                       assert(!is_workqueue_thread(kqr->kqr_thread));
+                       return;
+               }
+       }
+
+       /* Update sync ipc counts on kqr for suppressed knotes */
+       if (flags & KQWL_UO_UPDATE_SUPPRESS_SYNC_COUNTERS) {
+               kqworkloop_update_suppress_sync_count(kqr, flags);
+       }
+
+       if ((flags & KQWL_UO_UPDATE_OVERRIDE_LAZY) == 0) {
+               kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_WAKEUP_OVERRIDE,
+                       MAX(qos_index, override_index));
+       }
+       kqwl_req_unlock(kqwl);
+}
+
+static void
+kqworkloop_update_suppress_sync_count(
+       struct kqrequest *kqr,
+       uint32_t flags)
+{
+       if (flags & KQWL_UO_NEW_OVERRIDE_IS_SYNC_UI) {
+               kqr->kqr_sync_suppress_count++;
+       }
+
+       if (flags & KQWL_UO_OLD_OVERRIDE_IS_SYNC_UI) {
+               assert(kqr->kqr_sync_suppress_count > 0);
+               kqr->kqr_sync_suppress_count--;
+       }
+}
+
+/*
+ *     kqworkloop_unbind_thread - Unbind the servicer thread of a workloop kqueue
+ *
+ *     It will end the processing phase in case it was still processing:
+ *
+ *     We may have to request a new thread for not KQ_NO_WQ_THREAD workloop.
+ *     This can happen if :
+ *     - there were active events at or above our QoS we never got to (count > 0)
+ *     - we pended waitq hook callouts during processing
+ *     - we pended wakeups while processing (or unsuppressing)
+ *
+ *     Called with kqueue lock held.
+ */
+
+static void
+kqworkloop_unbind_thread(
+       struct kqworkloop *kqwl,
+       thread_t thread,
+       __unused unsigned int flags)
+{
+       struct kqueue *kq = &kqwl->kqwl_kqueue;
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+
+       kqlock_held(kq);
+
+       assert((kq->kq_state & KQ_PROCESSING) == 0);
+       if (kq->kq_state & KQ_PROCESSING) {
+               return;
+       }
+
+       /*
+        * Forcing the KQ_PROCESSING flag allows for QoS updates because of
+        * unsuppressing knotes not to be applied until the eventual call to
+        * kqworkloop_update_threads_qos() below.
+        */
+       kq->kq_state |= KQ_PROCESSING;
+       kqworkloop_acknowledge_events(kqwl, TRUE);
+       kq->kq_state &= ~KQ_PROCESSING;
+
+       kqwl_req_lock(kqwl);
+
+       /* deal with extraneous unbinds in release kernels */
+       assert((kqr->kqr_state & (KQR_BOUND | KQR_PROCESSING)) == KQR_BOUND);
+       if ((kqr->kqr_state & (KQR_BOUND | KQR_PROCESSING)) != KQR_BOUND) {
+               kqwl_req_unlock(kqwl);
+               return;
+       }
+
+       assert(thread == current_thread());
+       assert(kqr->kqr_thread == thread);
+       if (kqr->kqr_thread != thread) {
+               kqwl_req_unlock(kqwl);
+           return;
+       }
+
+       struct uthread *ut = get_bsdthread_info(thread);
+       kq_index_t old_qos_index = ut->uu_kqueue_qos_index;
+       boolean_t ipc_override_is_sync = ut->uu_kqueue_override_is_sync;
+       ut->uu_kqueue_bound = NULL;
+       ut->uu_kqueue_qos_index = 0;
+       ut->uu_kqueue_override_is_sync = 0;
+       ut->uu_kqueue_flags = 0;
+
+       /* unbind the servicer thread, drop overrides */
+       kqr->kqr_thread = NULL;
+       kqr->kqr_state &= ~(KQR_BOUND | KQR_THREQUESTED | KQR_R2K_NOTIF_ARMED);
+       kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_RECOMPUTE_WAKEUP_QOS, 0);
+
+       kqwl_req_unlock(kqwl);
+
+       /*
+        * Drop the override on the current thread last, after the call to
+        * kqworkloop_update_threads_qos above.
+        */
+       if (old_qos_index) {
+               thread_drop_ipc_override(thread);
+       }
+       if (ipc_override_is_sync) {
+               thread_drop_sync_ipc_override(thread);
+       }
+}
+
+/* called with the kqworkq lock held */
+static void
+kqworkq_unbind_thread(
+       struct kqworkq *kqwq,
+       kq_index_t qos_index,
+       thread_t thread, 
+       __unused unsigned int flags)
+{
+       struct kqrequest *kqr = kqworkq_get_request(kqwq, qos_index);
+       kq_index_t override_index = 0;
+
+       /* request lock must be held */
+       kqwq_req_held(kqwq);
+
+       assert(thread == current_thread());
+
+       if ((kqr->kqr_state & KQR_BOUND) == 0) {
+               assert(kqr->kqr_state & KQR_BOUND);
+               return;
+       }
+
+       assert(kqr->kqr_thread == thread);
+       assert(TAILQ_EMPTY(&kqr->kqr_suppressed));
+
+       /* 
+        * If there is an override, drop it from the current thread
+        * and then we are free to recompute (a potentially lower)
+        * minimum override to apply to the next thread request.
+        */
+       if (kqr->kqr_override_index) {
+               struct kqtailq *base_queue = kqueue_get_base_queue(&kqwq->kqwq_kqueue, qos_index);
+               struct kqtailq *queue = kqueue_get_high_queue(&kqwq->kqwq_kqueue, qos_index);
+
+               /* if not bound to a manager thread, drop the current ipc override */
+               if ((kqr->kqr_state & KQWQ_THMANAGER) == 0) {
+                       thread_drop_ipc_override(thread);
+               }
+
+               /* recompute the new override */
+               do {
+                       if (!TAILQ_EMPTY(queue)) {
+                               override_index = queue - base_queue + qos_index;
+                               break;
+                       }
+               } while (queue-- > base_queue);
+       }
+
+       /* Mark it unbound */
+       kqr->kqr_thread = NULL;
+       kqr->kqr_state &= ~(KQR_BOUND | KQR_THREQUESTED | KQWQ_THMANAGER);
+
+       /* apply the new override */
+       if (override_index > kqr->kqr_qos_index) {
+               kqr->kqr_override_index = override_index;
+       } else {
+               kqr->kqr_override_index = THREAD_QOS_UNSPECIFIED;
+       }
+}
+
+struct kqrequest *
+kqworkq_get_request(struct kqworkq *kqwq, kq_index_t qos_index)
+{
+       assert(qos_index < KQWQ_NQOS);
+       return &kqwq->kqwq_request[qos_index];
+}
+
+void
+knote_adjust_qos(struct knote *kn, qos_t new_qos, qos_t new_override, kq_index_t sync_override_index)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       boolean_t override_is_sync = FALSE;
+
+       if (kq->kq_state & (KQ_WORKQ | KQ_WORKLOOP)) {
+               kq_index_t new_qos_index;
+               kq_index_t new_override_index;
+               kq_index_t servicer_qos_index;
+
+               new_qos_index = qos_index_from_qos(kn, new_qos, FALSE);
+               new_override_index = qos_index_from_qos(kn, new_override, TRUE);
+
+               /* make sure the servicer qos acts as a floor */
+               servicer_qos_index = qos_index_from_qos(kn, kn->kn_qos, FALSE);
+               if (servicer_qos_index > new_qos_index)
+                       new_qos_index = servicer_qos_index;
+               if (servicer_qos_index > new_override_index)
+                       new_override_index = servicer_qos_index;
+               if (sync_override_index >= new_override_index) {
+                       new_override_index = sync_override_index;
+                       override_is_sync = TRUE;
+               }
+
+               kqlock(kq);
+               if (new_qos_index != knote_get_req_index(kn) ||
+                   new_override_index != knote_get_qos_override_index(kn) ||
+                   override_is_sync != kn->kn_qos_override_is_sync) {
+                       if (kn->kn_status & KN_QUEUED) {
+                               knote_dequeue(kn);
+                               knote_set_qos_index(kn, new_qos_index);
+                               knote_set_qos_override_index(kn, new_override_index, override_is_sync);
+                               knote_enqueue(kn);
+                               knote_wakeup(kn);
+                       } else {
+                               knote_set_qos_index(kn, new_qos_index);
+                               knote_set_qos_override_index(kn, new_override_index, override_is_sync);
+                       }
+               }
+               kqunlock(kq);
+       }
+}
+
+void
+knote_adjust_sync_qos(struct knote *kn, kq_index_t sync_qos, boolean_t lock_kq)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       kq_index_t old_sync_override;
+       kq_index_t qos_index = knote_get_qos_index(kn);
+       uint32_t flags = 0;
+
+       /* Tracking only happens for UI qos */
+       if (sync_qos != THREAD_QOS_USER_INTERACTIVE &&
+               sync_qos != THREAD_QOS_UNSPECIFIED) {
+               return;
+       }
+
+       if (lock_kq)
+               kqlock(kq);
+
+       if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               old_sync_override = knote_get_sync_qos_override_index(kn);
+               if (old_sync_override != sync_qos) {
+                       kn->kn_qos_sync_override = sync_qos;
+
+                       /* update sync ipc counters for suppressed knotes */
+                       if ((kn->kn_status & KN_SUPPRESSED) == KN_SUPPRESSED) {
+                               flags = flags | KQWL_UO_UPDATE_SUPPRESS_SYNC_COUNTERS;
+
+                               /* Do not recalculate kqwl override, it would be done later */
+                               flags = flags | KQWL_UO_UPDATE_OVERRIDE_LAZY;
+
+                               if (sync_qos == THREAD_QOS_USER_INTERACTIVE) {
+                                       flags = flags | KQWL_UO_NEW_OVERRIDE_IS_SYNC_UI;
+                               }
+
+                               if (old_sync_override == THREAD_QOS_USER_INTERACTIVE) {
+                                       flags = flags | KQWL_UO_OLD_OVERRIDE_IS_SYNC_UI;
+                               }
+
+                               kqworkloop_update_override(kqwl, qos_index, sync_qos,
+                                       flags);
+                       }
+
+               }
+       }
+       if (lock_kq)
+               kqunlock(kq);
+}
+
+static void
+knote_wakeup(struct knote *kn)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       kq_index_t qos_index = knote_get_qos_index(kn);
+
+       kqlock_held(kq);
+
+       if (kq->kq_state & KQ_WORKQ) {
+               /* request a servicing thread */
+               struct kqworkq *kqwq = (struct kqworkq *)kq;
+
+               kqworkq_request_help(kqwq, qos_index);
+
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               /* request a servicing thread */
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               if (kqworkloop_is_processing_on_current_thread(kqwl)) {
+                       /*
+                        * kqworkloop_end_processing() will perform the required QoS
+                        * computations when it unsets the processing mode.
+                        */
+                       return;
+               }
+               kqworkloop_request_help(kqwl, qos_index);
+       } else {
+               struct kqfile *kqf = (struct kqfile *)kq;
+
+               /* flag wakeups during processing */
+               if (kq->kq_state & KQ_PROCESSING)
+                       kq->kq_state |= KQ_WAKEUP;
+
+               /* wakeup a thread waiting on this queue */
+               if (kq->kq_state & (KQ_SLEEP | KQ_SEL)) {
+                       kq->kq_state &= ~(KQ_SLEEP | KQ_SEL);
+                       waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                          KQ_EVENT,
+                                          THREAD_AWAKENED,
+                                          WAITQ_ALL_PRIORITIES);
+               }
+
+               /* wakeup other kqueues/select sets we're inside */
+               KNOTE(&kqf->kqf_sel.si_note, 0);
+       }
+}
+
+/*
+ * Called with the kqueue locked
+ */
+static void
+kqueue_interrupt(struct kqueue *kq)
+{
+       assert((kq->kq_state & KQ_WORKQ) == 0);
+
+       /* wakeup sleeping threads */
+       if ((kq->kq_state & (KQ_SLEEP | KQ_SEL)) != 0) {
+               kq->kq_state &= ~(KQ_SLEEP | KQ_SEL);
+               (void)waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                        KQ_EVENT,
+                                        THREAD_RESTART,
+                                        WAITQ_ALL_PRIORITIES);
+       }
+
+       /* wakeup threads waiting their turn to process */
+       if (kq->kq_state & KQ_PROCWAIT) {
+               struct kqtailq *suppressq;
+
+               assert(kq->kq_state & KQ_PROCESSING);
+
+               kq->kq_state &= ~KQ_PROCWAIT;
+               suppressq = kqueue_get_suppressed_queue(kq, QOS_INDEX_KQFILE);
+               (void)waitq_wakeup64_all((struct waitq *)&kq->kq_wqs, 
+                                        CAST_EVENT64_T(suppressq),
+                                        THREAD_RESTART,
+                                        WAITQ_ALL_PRIORITIES);
+       }
+}
+
+/*
+ * Called back from waitq code when no threads waiting and the hook was set.
+ *
+ * Interrupts are likely disabled and spin locks are held - minimal work
+ * can be done in this context!!!
+ *
+ * JMM - in the future, this will try to determine which knotes match the
+ * wait queue wakeup and apply these wakeups against those knotes themselves.
+ * For now, all the events dispatched this way are dispatch-manager handled,
+ * so hard-code that for now.
+ */
+void
+waitq_set__CALLING_PREPOST_HOOK__(void *kq_hook, void *knote_hook, int qos)
+{
+#pragma unused(knote_hook, qos)
+
+       struct kqueue *kq = (struct kqueue *)kq_hook;
+
+       if (kq->kq_state & KQ_WORKQ) {
+               struct kqworkq *kqwq = (struct kqworkq *)kq;
+
+               kqworkq_request_help(kqwq, KQWQ_QOS_MANAGER);
+
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               kqworkloop_request_help(kqwl, KQWL_BUCKET_STAYACTIVE);
+       }
+}
+
+void
+klist_init(struct klist *list)
+{
+       SLIST_INIT(list);
+}
+
+
+/*
+ * Query/Post each knote in the object's list
+ *
+ *     The object lock protects the list. It is assumed
+ *     that the filter/event routine for the object can
+ *     determine that the object is already locked (via
+ *     the hint) and not deadlock itself.
+ *
+ *     The object lock should also hold off pending
+ *     detach/drop operations.  But we'll prevent it here
+ *     too (by taking a use reference) - just in case.
+ */
+void
+knote(struct klist *list, long hint)
+{
+       struct knote *kn;
+
+       SLIST_FOREACH(kn, list, kn_selnext) {
+               struct kqueue *kq = knote_get_kq(kn);
+
+               kqlock(kq);
+
+               assert(!knoteuse_needs_boost(kn, NULL));
+
+               /* If we can get a use reference - deliver event */
+               if (kqlock2knoteuse(kq, kn, KNUSE_NONE)) {
+                       int result;
+
+                       /* call the event with only a use count */
+                       result = knote_fops(kn)->f_event(kn, hint);
+
+                       /* if its not going away and triggered */
+                       if (knoteuse2kqlock(kq, kn, KNUSE_NONE) && result)
+                               knote_activate(kn);
+                       /* kq lock held */
+               }
+               kqunlock(kq);
+       }
+}
+
+/*
+ * attach a knote to the specified list.  Return true if this is the first entry.
+ * The list is protected by whatever lock the object it is associated with uses.
+ */
+int
+knote_attach(struct klist *list, struct knote *kn)
+{
+       int ret = SLIST_EMPTY(list);
+       SLIST_INSERT_HEAD(list, kn, kn_selnext);
+       return (ret);
+}
+
+/*
+ * detach a knote from the specified list.  Return true if that was the last entry.
+ * The list is protected by whatever lock the object it is associated with uses.
+ */
+int
+knote_detach(struct klist *list, struct knote *kn)
+{
+       SLIST_REMOVE(list, kn, knote, kn_selnext);
+       return (SLIST_EMPTY(list));
+}
+
+/*
+ * knote_vanish - Indicate that the source has vanished
+ *
+ * If the knote has requested EV_VANISHED delivery,
+ * arrange for that. Otherwise, deliver a NOTE_REVOKE
+ * event for backward compatibility.
+ *
+ * The knote is marked as having vanished, but is not
+ * actually detached from the source in this instance.
+ * The actual detach is deferred until the knote drop.
+ *
+ * Our caller already has the object lock held. Calling
+ * the detach routine would try to take that lock
+ * recursively - which likely is not supported.
+ */
+void
+knote_vanish(struct klist *list)
+{
+       struct knote *kn;
+       struct knote *kn_next;
+
+       SLIST_FOREACH_SAFE(kn, list, kn_selnext, kn_next) {
+               struct kqueue *kq = knote_get_kq(kn);
+               int result;
+
+               kqlock(kq);
+
+               assert(!knoteuse_needs_boost(kn, NULL));
+
+               if ((kn->kn_status & KN_DROPPING) == 0) {
+                       /* If EV_VANISH supported - prepare to deliver one */
+                       if (kn->kn_status & KN_REQVANISH) {
+                               kn->kn_status |= KN_VANISHED;
+                               knote_activate(kn);
+
+                       } else if (kqlock2knoteuse(kq, kn, KNUSE_NONE)) {
+                               /* call the event with only a use count */
+                               result = knote_fops(kn)->f_event(kn, NOTE_REVOKE);
+
+                               /* if its not going away and triggered */
+                               if (knoteuse2kqlock(kq, kn, KNUSE_NONE) && result)
+                                       knote_activate(kn);
+                               /* lock held again */
+                       }
+               }
+               kqunlock(kq);
+       }
+}
+
+/*
+ * For a given knote, link a provided wait queue directly with the kqueue.
+ * Wakeups will happen via recursive wait queue support.  But nothing will move
+ * the knote to the active list at wakeup (nothing calls knote()).  Instead,
+ * we permanently enqueue them here.
+ *
+ * kqueue and knote references are held by caller.
+ * waitq locked by caller.
+ *
+ * caller provides the wait queue link structure.
+ */
+int
+knote_link_waitq(struct knote *kn, struct waitq *wq, uint64_t *reserved_link)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       kern_return_t kr;
+
+       kr = waitq_link(wq, &kq->kq_wqs, WAITQ_ALREADY_LOCKED, reserved_link);
+       if (kr == KERN_SUCCESS) {
+               knote_markstayactive(kn);
+               return (0);
+       } else {
+               return (EINVAL);
+       }
+}
+
+/*
+ * Unlink the provided wait queue from the kqueue associated with a knote.
+ * Also remove it from the magic list of directly attached knotes.
+ *
+ * Note that the unlink may have already happened from the other side, so
+ * ignore any failures to unlink and just remove it from the kqueue list.
+ *
+ * On success, caller is responsible for the link structure
+ */
+int
+knote_unlink_waitq(struct knote *kn, struct waitq *wq)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       kern_return_t kr;
+
+       kr = waitq_unlink(wq, &kq->kq_wqs);
+       knote_clearstayactive(kn);
+       return ((kr != KERN_SUCCESS) ? EINVAL : 0);
+}
+
+/*
+ * remove all knotes referencing a specified fd
+ *
+ * Essentially an inlined knote_remove & knote_drop
+ * when we know for sure that the thing is a file
+ *
+ * Entered with the proc_fd lock already held.
+ * It returns the same way, but may drop it temporarily.
+ */
+void
+knote_fdclose(struct proc *p, int fd, int force)
+{
+       struct klist *list;
+       struct knote *kn;
+
+restart:
+       list = &p->p_fd->fd_knlist[fd];
+       SLIST_FOREACH(kn, list, kn_link) {
+               struct kqueue *kq = knote_get_kq(kn);
+
+               kqlock(kq);
+
+               if (kq->kq_p != p)
+                       panic("%s: proc mismatch (kq->kq_p=%p != p=%p)",
+                           __func__, kq->kq_p, p);
+
+               /*
+                * If the knote supports EV_VANISHED delivery,
+                * transition it to vanished mode (or skip over
+                * it if already vanished).
+                */
+               if (!force && (kn->kn_status & KN_REQVANISH)) {
+
+                       if ((kn->kn_status & KN_VANISHED) == 0) {
+                               proc_fdunlock(p);
+
+                               assert(!knoteuse_needs_boost(kn, NULL));
+
+                               /* get detach reference (also marks vanished) */
+                               if (kqlock2knotedetach(kq, kn, KNUSE_NONE)) {
+                                       /* detach knote and drop fp use reference */
+                                       knote_fops(kn)->f_detach(kn);
+                                       if (knote_fops(kn)->f_isfd)
+                                               fp_drop(p, kn->kn_id, kn->kn_fp, 0);
+
+                                       /* activate it if it's still in existence */
+                                       if (knoteuse2kqlock(kq, kn, KNUSE_NONE)) {
+                                               knote_activate(kn);
+                                       }
+                                       kqunlock(kq);
+                               }
+                               proc_fdlock(p);
+                               goto restart;
+                       } else {
+                               kqunlock(kq);
+                               continue;
+                       }
+               }
+
+               proc_fdunlock(p);
+
+               /*
+                * Convert the kq lock to a drop ref.
+                * If we get it, go ahead and drop it.
+                * Otherwise, we waited for the blocking
+                * condition to complete. Either way,
+                * we dropped the fdlock so start over.
+                */
+               if (kqlock2knotedrop(kq, kn)) {
+                       knote_drop(kn, p);
+               }
+
+               proc_fdlock(p);
+               goto restart;
+       }
+}
+
+/* 
+ * knote_fdfind - lookup a knote in the fd table for process
+ *
+ * If the filter is file-based, lookup based on fd index.
+ * Otherwise use a hash based on the ident.
+ *
+ * Matching is based on kq, filter, and ident. Optionally,
+ * it may also be based on the udata field in the kevent -
+ * allowing multiple event registration for the file object
+ * per kqueue.
+ *
+ * fd_knhashlock or fdlock held on entry (and exit)
+ */
+static struct knote *
+knote_fdfind(struct kqueue *kq,
+             struct kevent_internal_s *kev,
+            bool is_fd,
+             struct proc *p)
+{
+       struct filedesc *fdp = p->p_fd;
+       struct klist *list = NULL;
+       struct knote *kn = NULL;
+
+       /* 
+        * determine where to look for the knote
+        */
+       if (is_fd) {
+               /* fd-based knotes are linked off the fd table */
+               if (kev->ident < (u_int)fdp->fd_knlistsize) {
+                       list = &fdp->fd_knlist[kev->ident];
+               }
+       } else if (fdp->fd_knhashmask != 0) {
+               /* hash non-fd knotes here too */
+               list = &fdp->fd_knhash[KN_HASH((u_long)kev->ident, fdp->fd_knhashmask)];
+       }
+
+       /*
+        * scan the selected list looking for a match
+        */
+       if (list != NULL) {
+               SLIST_FOREACH(kn, list, kn_link) {
+                       if (kq == knote_get_kq(kn) &&
+                           kev->ident == kn->kn_id && 
+                           kev->filter == kn->kn_filter) {
+                               if (kev->flags & EV_UDATA_SPECIFIC) {
+                                       if ((kn->kn_status & KN_UDATA_SPECIFIC) &&
+                                           kev->udata == kn->kn_udata) {
+                                               break; /* matching udata-specific knote */
+                                       }
+                               } else if ((kn->kn_status & KN_UDATA_SPECIFIC) == 0) {
+                                       break; /* matching non-udata-specific knote */
+                               }
+                       }
+               }
+       }
+       return kn;
+}
+
+/*
+ * kq_add_knote- Add knote to the fd table for process
+ * while checking for duplicates.
+ *
+ * All file-based filters associate a list of knotes by file
+ * descriptor index. All other filters hash the knote by ident.
+ *
+ * May have to grow the table of knote lists to cover the
+ * file descriptor index presented.
+ *
+ * fd_knhashlock and fdlock unheld on entry (and exit).
+ *
+ * Takes a rwlock boost if inserting the knote is successful.
+ */
+static int
+kq_add_knote(struct kqueue *kq, struct knote *kn,
+             struct kevent_internal_s *kev,
+             struct proc *p, int *knoteuse_flags)
+{
+       struct filedesc *fdp = p->p_fd;
+       struct klist *list = NULL;
+       int ret = 0;
+       bool is_fd = knote_fops(kn)->f_isfd;
+
+       if (is_fd)
+               proc_fdlock(p);
+       else
+               knhash_lock(p);
+
+       if (knote_fdfind(kq, kev, is_fd, p) != NULL) {
+               /* found an existing knote: we can't add this one */
+               ret = ERESTART;
+               goto out_locked;
+       }
+
+       /* knote was not found: add it now */
+       if (!is_fd) {
+               if (fdp->fd_knhashmask == 0) {
+                       u_long size = 0;
+
+                       list = hashinit(CONFIG_KN_HASHSIZE, M_KQUEUE,
+                                                 &size);
+                       if (list == NULL) {
+                               ret = ENOMEM;
+                               goto out_locked;
+                       }
+
+                       fdp->fd_knhash = list;
+                       fdp->fd_knhashmask = size;
+               }
+
+               list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
+               SLIST_INSERT_HEAD(list, kn, kn_link);
+               ret = 0;
+               goto out_locked;
+
+       } else {
+               /* knote is fd based */
+
+               if ((u_int)fdp->fd_knlistsize <= kn->kn_id) {
+                       u_int size = 0;
+
+                       if (kn->kn_id >= (uint64_t)p->p_rlimit[RLIMIT_NOFILE].rlim_cur
+                           || kn->kn_id >= (uint64_t)maxfiles) {
+                               ret = EINVAL;
+                               goto out_locked;
+                       }
+                       /* have to grow the fd_knlist */
+                       size = fdp->fd_knlistsize;
+                       while (size <= kn->kn_id)
+                               size += KQEXTENT;
+
+                       if (size >= (UINT_MAX/sizeof(struct klist *))) {
+                               ret = EINVAL;
+                               goto out_locked;
+                       }
+
+                       MALLOC(list, struct klist *,
+                           size * sizeof(struct klist *), M_KQUEUE, M_WAITOK);
+                       if (list == NULL) {
+                               ret = ENOMEM;
+                               goto out_locked;
+                       }
+
+                       bcopy((caddr_t)fdp->fd_knlist, (caddr_t)list,
+                           fdp->fd_knlistsize * sizeof(struct klist *));
+                       bzero((caddr_t)list +
+                           fdp->fd_knlistsize * sizeof(struct klist *),
+                           (size - fdp->fd_knlistsize) * sizeof(struct klist *));
+                       FREE(fdp->fd_knlist, M_KQUEUE);
+                       fdp->fd_knlist = list;
+                       fdp->fd_knlistsize = size;
+               }
+
+               list = &fdp->fd_knlist[kn->kn_id];
+               SLIST_INSERT_HEAD(list, kn, kn_link);
+               ret = 0;
+               goto out_locked;
+
+       }
+
+out_locked:
+       if (ret == 0 && knoteuse_needs_boost(kn, kev)) {
+               set_thread_rwlock_boost();
+               *knoteuse_flags = KNUSE_BOOST;
+       } else {
+               *knoteuse_flags = KNUSE_NONE;
+       }
+       if (is_fd)
+               proc_fdunlock(p);
+       else
+               knhash_unlock(p);
+
+       return ret;
+}
+
+/*
+ * kq_remove_knote - remove a knote from the fd table for process
+ * and copy kn_status an kq_state while holding kqlock and
+ * fd table locks.
+ *
+ * If the filter is file-based, remove based on fd index.
+ * Otherwise remove from the hash based on the ident.
+ *
+ * fd_knhashlock and fdlock unheld on entry (and exit).
+ */
+static void
+kq_remove_knote(struct kqueue *kq, struct knote *kn, struct proc *p,
+       kn_status_t *kn_status, uint16_t *kq_state)
+{
+       struct filedesc *fdp = p->p_fd;
+       struct klist *list = NULL;
+       bool is_fd;
+
+       is_fd = knote_fops(kn)->f_isfd;
+
+       if (is_fd)
+               proc_fdlock(p);
+       else
+               knhash_lock(p);
+
+       if (is_fd) {
+               assert ((u_int)fdp->fd_knlistsize > kn->kn_id);
+               list = &fdp->fd_knlist[kn->kn_id];
+       } else {
+               list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
+       }
+       SLIST_REMOVE(list, kn, knote, kn_link);
+
+       kqlock(kq);
+       *kn_status = kn->kn_status;
+       *kq_state = kq->kq_state;
+       kqunlock(kq);
+
+       if (is_fd)
+               proc_fdunlock(p);
+       else
+               knhash_unlock(p);
+}
+
+/*
+ * kq_find_knote_and_kq_lock - lookup a knote in the fd table for process
+ * and, if the knote is found, acquires the kqlock while holding the fd table lock/spinlock.
+ *
+ * fd_knhashlock or fdlock unheld on entry (and exit)
+ */
+
+static struct knote *
+kq_find_knote_and_kq_lock(struct kqueue *kq,
+             struct kevent_internal_s *kev,
+            bool is_fd,
+             struct proc *p)
+{
+       struct knote * ret;
+
+       if (is_fd)
+               proc_fdlock(p);
+       else
+               knhash_lock(p);
+
+       ret = knote_fdfind(kq, kev, is_fd, p);
+
+       if (ret) {
+               kqlock(kq);
+       }
+
+       if (is_fd)
+               proc_fdunlock(p);
+       else
+               knhash_unlock(p);
+
+       return ret;
+}
+/*
+ * knote_drop - disconnect and drop the knote
+ *
+ * Called with the kqueue unlocked and holding a
+ * "drop reference" on the knote in question.
+ * This reference is most often aquired thru a call
+ * to kqlock2knotedrop(). But it can also be acquired
+ * through stealing a drop reference via a call to
+ * knoteuse2knotedrop() or during the initial attach
+ * of the knote.
+ *
+ * The knote may have already been detached from
+ * (or not yet attached to) its source object.
+ */
+static void
+knote_drop(struct knote *kn, __unused struct proc *ctxp)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       struct proc *p = kq->kq_p;
+       kn_status_t kn_status;
+       uint16_t kq_state;
+
+       /* If we are attached, disconnect from the source first */
+       if (kn->kn_status & KN_ATTACHED) {
+               knote_fops(kn)->f_detach(kn);
+       }
+
+       /* Remove the source from the appropriate hash */
+       kq_remove_knote(kq, kn, p, &kn_status, &kq_state);
+
+       /*
+        * If a kqueue_dealloc is happening in parallel for the kq
+        * pointed by the knote the kq could be aready deallocated
+        * at this point.
+        * Do not access the kq after the kq_remove_knote if it is
+        * not a KQ_DYNAMIC.
+        */
+
+       /* determine if anyone needs to know about the drop */
+       assert((kn_status & (KN_DROPPING | KN_SUPPRESSED | KN_QUEUED)) == KN_DROPPING);
+
+       /*
+        * If KN_USEWAIT is set, some other thread was trying to drop the kn.
+        * Or it was in kqueue_dealloc, so the kqueue_dealloc did not happen
+        * because that thread was waiting on this wake, or it was a drop happening
+        * because of a kevent_register that takes a reference on the kq, and therefore
+        * the kq cannot be deallocated in parallel.
+        *
+        * It is safe to access kq->kq_wqs if needswakeup is set.
+        */
+       if (kn_status & KN_USEWAIT)
+               waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
+                                  CAST_EVENT64_T(&kn->kn_status),
+                                  THREAD_RESTART,
+                                  WAITQ_ALL_PRIORITIES);
+
+       if (knote_fops(kn)->f_isfd && ((kn->kn_status & KN_VANISHED) == 0))
+               fp_drop(p, kn->kn_id, kn->kn_fp, 0);
+
+       knote_free(kn);
+
+       /*
+        * release reference on dynamic kq (and free if last).
+        * Will only be last if this is from fdfree, etc...
+        * because otherwise processing thread has reference.
+        */
+       if (kq_state & KQ_DYNAMIC)
+               kqueue_release_last(p, kq);
+}
+
+/* called with kqueue lock held */
+static void
+knote_activate(struct knote *kn)
+{
+       if (kn->kn_status & KN_ACTIVE)
+               return;
+
+       KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KNOTE_ACTIVATE),
+                     kn->kn_udata, kn->kn_status | (kn->kn_id << 32),
+                     kn->kn_filtid);
+
+       kn->kn_status |= KN_ACTIVE;
+       if (knote_enqueue(kn))
+               knote_wakeup(kn);
+}
+
+/* called with kqueue lock held */
+static void
+knote_deactivate(struct knote *kn)
+{
+       kn->kn_status &= ~KN_ACTIVE;
+       if ((kn->kn_status & KN_STAYACTIVE) == 0)
+               knote_dequeue(kn);
+}
+
+/* called with kqueue lock held */
+static void
+knote_enable(struct knote *kn)
+{
+       if ((kn->kn_status & KN_DISABLED) == 0)
+               return;
+
+       kn->kn_status &= ~KN_DISABLED;
+
+       if (kn->kn_status & KN_SUPPRESSED) {
+               /* Clear the sync qos on the knote */
+               knote_adjust_sync_qos(kn, THREAD_QOS_UNSPECIFIED, FALSE);
+
+               /*
+                * it is possible for userland to have knotes registered for a given
+                * workloop `wl_orig` but really handled on another workloop `wl_new`.
+                *
+                * In that case, rearming will happen from the servicer thread of
+                * `wl_new` which if `wl_orig` is no longer being serviced, would cause
+                * this knote to stay suppressed forever if we only relied on
+                * kqworkloop_acknowledge_events to be called by `wl_orig`.
+                *
+                * However if we see the KQ_PROCESSING bit on `wl_orig` set, we can't
+                * unsuppress because that would mess with the processing phase of
+                * `wl_orig`, however it also means kqworkloop_acknowledge_events()
+                * will be called.
+                */
+               struct kqueue *kq = knote_get_kq(kn);
+               if ((kq->kq_state & KQ_PROCESSING) == 0) {
+                       knote_unsuppress(kn);
+               }
+       } else if (knote_enqueue(kn)) {
+               knote_wakeup(kn);
+       }
+}
+
+/* called with kqueue lock held */
+static void
+knote_disable(struct knote *kn)
+{
+       if (kn->kn_status & KN_DISABLED)
+               return;
+
+       kn->kn_status |= KN_DISABLED;
+       knote_dequeue(kn);
+}
+
+/* called with kqueue lock held */
+static void
+knote_suppress(struct knote *kn)
+{
+       struct kqtailq *suppressq;
+       struct kqueue *kq = knote_get_kq(kn);
+
+       kqlock_held(kq);
+
+       if (kn->kn_status & KN_SUPPRESSED)
+               return;
+
+       knote_dequeue(kn);
+       kn->kn_status |= KN_SUPPRESSED;
+       suppressq = kqueue_get_suppressed_queue(kq, knote_get_qos_index(kn));
+       TAILQ_INSERT_TAIL(suppressq, kn, kn_tqe);
+
+       if ((kq->kq_state & KQ_WORKLOOP) &&
+            knote_get_qos_override_index(kn) == THREAD_QOS_USER_INTERACTIVE &&
+            kn->kn_qos_override_is_sync) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+               /* update the sync qos override counter for suppressed knotes */
+               kqworkloop_update_override(kqwl, knote_get_qos_index(kn),
+                       knote_get_qos_override_index(kn),
+                       (KQWL_UO_UPDATE_SUPPRESS_SYNC_COUNTERS | KQWL_UO_NEW_OVERRIDE_IS_SYNC_UI));
+       }
+}
+
+/* called with kqueue lock held */
+static void
+knote_unsuppress(struct knote *kn)
+{
+       struct kqtailq *suppressq;
+       struct kqueue *kq = knote_get_kq(kn);
+
+       kqlock_held(kq);
+
+       if ((kn->kn_status & KN_SUPPRESSED) == 0)
+               return;
+
+       /* Clear the sync qos on the knote */
+       knote_adjust_sync_qos(kn, THREAD_QOS_UNSPECIFIED, FALSE);
+
+       kn->kn_status &= ~KN_SUPPRESSED;
+       suppressq = kqueue_get_suppressed_queue(kq, knote_get_qos_index(kn));
+       TAILQ_REMOVE(suppressq, kn, kn_tqe);
+
+       /* udate in-use qos to equal requested qos */
+       kn->kn_qos_index = kn->kn_req_index;
+
+       /* don't wakeup if unsuppressing just a stay-active knote */
+       if (knote_enqueue(kn) && (kn->kn_status & KN_ACTIVE)) {
+               knote_wakeup(kn);
+       }
+
+       if ((kq->kq_state & KQ_WORKLOOP) && !(kq->kq_state & KQ_NO_WQ_THREAD) &&
+            knote_get_qos_override_index(kn) == THREAD_QOS_USER_INTERACTIVE &&
+            kn->kn_qos_override_is_sync) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+
+               /* update the sync qos override counter for suppressed knotes */
+               kqworkloop_update_override(kqwl, knote_get_qos_index(kn),
+                       knote_get_qos_override_index(kn),
+                       (KQWL_UO_UPDATE_SUPPRESS_SYNC_COUNTERS | KQWL_UO_OLD_OVERRIDE_IS_SYNC_UI));
+       }
+
+       if (TAILQ_EMPTY(suppressq) && (kq->kq_state & KQ_WORKLOOP) &&
+                       !(kq->kq_state & KQ_NO_WQ_THREAD)) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+               if (kqworkloop_is_processing_on_current_thread(kqwl)) {
+                       /*
+                        * kqworkloop_end_processing() will perform the required QoS
+                        * computations when it unsets the processing mode.
+                        */
+               } else {
+                       kqwl_req_lock(kqwl);
+                       kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_RESET_WAKEUP_OVERRIDE, 0);
+                       kqwl_req_unlock(kqwl);
+               }
+       }
+}
+
+/* called with kqueue lock held */
+static void
+knote_update_sync_override_state(struct knote *kn)
+{
+       struct kqtailq *queue = knote_get_queue(kn);
+       struct kqueue *kq = knote_get_kq(kn);
+
+       if (!(kq->kq_state & KQ_WORKLOOP) ||
+           knote_get_queue_index(kn) != THREAD_QOS_USER_INTERACTIVE)
+               return;
+
+       /* Update the sync ipc state on workloop */
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       boolean_t sync_ipc_override = FALSE;
+       if (!TAILQ_EMPTY(queue)) {
+               struct knote *kn_head = TAILQ_FIRST(queue);
+               if (kn_head->kn_qos_override_is_sync)
+                       sync_ipc_override = TRUE;
+       }
+       kqworkloop_update_sync_override_state(kqwl, sync_ipc_override);
+}
+
+/* called with kqueue lock held */
+static int
+knote_enqueue(struct knote *kn)
+{
+       if ((kn->kn_status & (KN_ACTIVE | KN_STAYACTIVE)) == 0 ||
+           (kn->kn_status & (KN_DISABLED | KN_SUPPRESSED | KN_DROPPING)))
+               return 0;
+
+       if ((kn->kn_status & KN_QUEUED) == 0) {
+               struct kqtailq *queue = knote_get_queue(kn);
+               struct kqueue *kq = knote_get_kq(kn);
+
+               kqlock_held(kq);
+               /* insert at head for sync ipc waiters */
+               if (kn->kn_qos_override_is_sync) {
+                       TAILQ_INSERT_HEAD(queue, kn, kn_tqe);
+               } else {
+                       TAILQ_INSERT_TAIL(queue, kn, kn_tqe);
+               }
+               kn->kn_status |= KN_QUEUED;
+               kq->kq_count++;
+               knote_update_sync_override_state(kn);
+               return 1;
+       }
+       return ((kn->kn_status & KN_STAYACTIVE) != 0);
+}
+
+
+/* called with kqueue lock held */
+static void
+knote_dequeue(struct knote *kn)
+{
+       struct kqueue *kq = knote_get_kq(kn);
+       struct kqtailq *queue;
+
+       kqlock_held(kq);
+
+       if ((kn->kn_status & KN_QUEUED) == 0)
+               return;
+
+       queue = knote_get_queue(kn);
+       TAILQ_REMOVE(queue, kn, kn_tqe);
+       kn->kn_status &= ~KN_QUEUED;
+       kq->kq_count--;
+       knote_update_sync_override_state(kn);
+}
+
+void
+knote_init(void)
+{
+       knote_zone = zinit(sizeof(struct knote), 8192*sizeof(struct knote),
+                          8192, "knote zone");
+
+       kqfile_zone = zinit(sizeof(struct kqfile), 8192*sizeof(struct kqfile),
+                           8192, "kqueue file zone");
+
+       kqworkq_zone = zinit(sizeof(struct kqworkq), 8192*sizeof(struct kqworkq),
+                           8192, "kqueue workq zone");
+
+       kqworkloop_zone = zinit(sizeof(struct kqworkloop), 8192*sizeof(struct kqworkloop),
+                           8192, "kqueue workloop zone");
+
+       /* allocate kq lock group attribute and group */
+       kq_lck_grp_attr = lck_grp_attr_alloc_init();
+
+       kq_lck_grp = lck_grp_alloc_init("kqueue",  kq_lck_grp_attr);
+
+       /* Allocate kq lock attribute */
+       kq_lck_attr = lck_attr_alloc_init();
+
+       /* Initialize the timer filter lock */
+       lck_mtx_init(&_filt_timerlock, kq_lck_grp, kq_lck_attr);
+
+       /* Initialize the user filter lock */
+       lck_spin_init(&_filt_userlock, kq_lck_grp, kq_lck_attr);
+
+#if CONFIG_MEMORYSTATUS
+       /* Initialize the memorystatus list lock */
+       memorystatus_kevent_init(kq_lck_grp, kq_lck_attr);
+#endif
+}
+SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_ANY, knote_init, NULL)
+
+const struct filterops *
+knote_fops(struct knote *kn)
+{
+       return sysfilt_ops[kn->kn_filtid];
+}
+
+static struct knote *
+knote_alloc(void)
+{
+       struct knote *kn;
+       kn = ((struct knote *)zalloc(knote_zone));
+       *kn = (struct knote) { .kn_qos_override = 0, .kn_qos_sync_override = 0, .kn_qos_override_is_sync = 0 };
+       return kn;
+}
+
+static void
+knote_free(struct knote *kn)
+{
+       zfree(knote_zone, kn);
+}
 
-               switch (wait_result) {
-               case THREAD_AWAKENED:
-                       continue;
-               case THREAD_TIMED_OUT:
-                       return EWOULDBLOCK; 
-               case THREAD_INTERRUPTED:
-                       return EINTR;
-               default:
-                       panic("kevent_scan - bad wait_result (%d)",
-                             wait_result);
-                       error = 0;
-               }
+#if SOCKETS
+#include <sys/param.h>
+#include <sys/socket.h>
+#include <sys/protosw.h>
+#include <sys/domain.h>
+#include <sys/mbuf.h>
+#include <sys/kern_event.h>
+#include <sys/malloc.h>
+#include <sys/sys_domain.h>
+#include <sys/syslog.h>
+
+#ifndef ROUNDUP64
+#define        ROUNDUP64(x) P2ROUNDUP((x), sizeof (u_int64_t))
+#endif
+
+#ifndef ADVANCE64
+#define        ADVANCE64(p, n) (void*)((char *)(p) + ROUNDUP64(n))
+#endif
+
+static lck_grp_attr_t *kev_lck_grp_attr;
+static lck_attr_t *kev_lck_attr;
+static lck_grp_t *kev_lck_grp;
+static decl_lck_rw_data(,kev_lck_data);
+static lck_rw_t *kev_rwlock = &kev_lck_data;
+
+static int kev_attach(struct socket *so, int proto, struct proc *p);
+static int kev_detach(struct socket *so);
+static int kev_control(struct socket *so, u_long cmd, caddr_t data,
+    struct ifnet *ifp, struct proc *p);
+static lck_mtx_t * event_getlock(struct socket *, int);
+static int event_lock(struct socket *, int, void *);
+static int event_unlock(struct socket *, int, void *);
+
+static int event_sofreelastref(struct socket *);
+static void kev_delete(struct kern_event_pcb *);
+
+static struct pr_usrreqs event_usrreqs = {
+       .pru_attach =           kev_attach,
+       .pru_control =          kev_control,
+       .pru_detach =           kev_detach,
+       .pru_soreceive =        soreceive,
+};
+
+static struct protosw eventsw[] = {
+{
+       .pr_type =              SOCK_RAW,
+       .pr_protocol =          SYSPROTO_EVENT,
+       .pr_flags =             PR_ATOMIC,
+       .pr_usrreqs =           &event_usrreqs,
+       .pr_lock =              event_lock,
+       .pr_unlock =            event_unlock,
+       .pr_getlock =           event_getlock,
+}
+};
+
+__private_extern__ int kevt_getstat SYSCTL_HANDLER_ARGS;
+__private_extern__ int kevt_pcblist SYSCTL_HANDLER_ARGS;
+
+SYSCTL_NODE(_net_systm, OID_AUTO, kevt,
+       CTLFLAG_RW|CTLFLAG_LOCKED, 0, "Kernel event family");
+
+struct kevtstat kevtstat;
+SYSCTL_PROC(_net_systm_kevt, OID_AUTO, stats,
+    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
+    kevt_getstat, "S,kevtstat", "");
+
+SYSCTL_PROC(_net_systm_kevt, OID_AUTO, pcblist,
+       CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
+       kevt_pcblist, "S,xkevtpcb", "");
+
+static lck_mtx_t *
+event_getlock(struct socket *so, int flags)
+{
+#pragma unused(flags)
+       struct kern_event_pcb *ev_pcb = (struct kern_event_pcb *)so->so_pcb;
+
+       if (so->so_pcb != NULL)  {
+               if (so->so_usecount < 0)
+                       panic("%s: so=%p usecount=%d lrh= %s\n", __func__,
+                           so, so->so_usecount, solockhistory_nr(so));
+                       /* NOTREACHED */
+       } else {
+               panic("%s: so=%p NULL NO so_pcb %s\n", __func__,
+                   so, solockhistory_nr(so));
+               /* NOTREACHED */
        }
-       kqunlock(kq);
-       return error;
+       return (&ev_pcb->evp_mtx);
 }
 
+static int
+event_lock(struct socket *so, int refcount, void *lr)
+{
+       void *lr_saved;
+
+       if (lr == NULL)
+               lr_saved = __builtin_return_address(0);
+       else
+               lr_saved = lr;
+
+       if (so->so_pcb != NULL) {
+               lck_mtx_lock(&((struct kern_event_pcb *)so->so_pcb)->evp_mtx);
+       } else  {
+               panic("%s: so=%p NO PCB! lr=%p lrh= %s\n", __func__,
+                   so, lr_saved, solockhistory_nr(so));
+               /* NOTREACHED */
+       }
+
+       if (so->so_usecount < 0) {
+               panic("%s: so=%p so_pcb=%p lr=%p ref=%d lrh= %s\n", __func__,
+                   so, so->so_pcb, lr_saved, so->so_usecount,
+                   solockhistory_nr(so));
+               /* NOTREACHED */
+       }
+
+       if (refcount)
+               so->so_usecount++;
+
+       so->lock_lr[so->next_lock_lr] = lr_saved;
+       so->next_lock_lr = (so->next_lock_lr+1) % SO_LCKDBG_MAX;
+       return (0);
+}
 
-/*
- * XXX
- * This could be expanded to call kqueue_scan, if desired.
- */
-/*ARGSUSED*/
 static int
-kqueue_read(__unused struct fileproc *fp, 
-                       __unused struct uio *uio, 
-                       __unused int flags, 
-                       __unused vfs_context_t ctx)
+event_unlock(struct socket *so, int refcount, void *lr)
 {
-       return (ENXIO);
+       void *lr_saved;
+       lck_mtx_t *mutex_held;
+
+       if (lr == NULL)
+               lr_saved = __builtin_return_address(0);
+       else
+               lr_saved = lr;
+
+       if (refcount) {
+               so->so_usecount--;
+       }
+       if (so->so_usecount < 0) {
+               panic("%s: so=%p usecount=%d lrh= %s\n", __func__,
+                   so, so->so_usecount, solockhistory_nr(so));
+               /* NOTREACHED */
+       }
+       if (so->so_pcb == NULL) {
+               panic("%s: so=%p NO PCB usecount=%d lr=%p lrh= %s\n", __func__,
+                   so, so->so_usecount, (void *)lr_saved,
+                   solockhistory_nr(so));
+               /* NOTREACHED */
+       }
+       mutex_held = (&((struct kern_event_pcb *)so->so_pcb)->evp_mtx);
+
+       LCK_MTX_ASSERT(mutex_held, LCK_MTX_ASSERT_OWNED);
+       so->unlock_lr[so->next_unlock_lr] = lr_saved;
+       so->next_unlock_lr = (so->next_unlock_lr+1) % SO_LCKDBG_MAX;
+
+       if (so->so_usecount == 0) {
+               VERIFY(so->so_flags & SOF_PCBCLEARING);
+               event_sofreelastref(so);
+       } else {
+               lck_mtx_unlock(mutex_held);
+       }
+
+       return (0);
 }
 
-/*ARGSUSED*/
 static int
-kqueue_write(__unused struct fileproc *fp, 
-                        __unused struct uio *uio, 
-                        __unused int flags, 
-                        __unused vfs_context_t ctx)
+event_sofreelastref(struct socket *so)
 {
-       return (ENXIO);
+       struct kern_event_pcb *ev_pcb = (struct kern_event_pcb *)so->so_pcb;
+
+       LCK_MTX_ASSERT(&(ev_pcb->evp_mtx), LCK_MTX_ASSERT_OWNED);
+
+       so->so_pcb = NULL;
+
+       /*
+        * Disable upcall in the event another thread is in kev_post_msg()
+        * appending record to the receive socket buffer, since sbwakeup()
+        * may release the socket lock otherwise.
+        */
+       so->so_rcv.sb_flags &= ~SB_UPCALL;
+       so->so_snd.sb_flags &= ~SB_UPCALL;
+       so->so_event = sonullevent;
+       lck_mtx_unlock(&(ev_pcb->evp_mtx));
+
+       LCK_MTX_ASSERT(&(ev_pcb->evp_mtx), LCK_MTX_ASSERT_NOTOWNED);
+       lck_rw_lock_exclusive(kev_rwlock);
+       LIST_REMOVE(ev_pcb, evp_link);
+       kevtstat.kes_pcbcount--;
+       kevtstat.kes_gencnt++;
+       lck_rw_done(kev_rwlock);
+       kev_delete(ev_pcb);
+
+       sofreelastref(so, 1);
+       return (0);
+}
+
+static int event_proto_count = (sizeof (eventsw) / sizeof (struct protosw));
+
+static
+struct kern_event_head kern_event_head;
+
+static u_int32_t static_event_id = 0;
+
+#define        EVPCB_ZONE_MAX          65536
+#define        EVPCB_ZONE_NAME         "kerneventpcb"
+static struct zone *ev_pcb_zone;
+
+/*
+ * Install the protosw's for the NKE manager.  Invoked at extension load time
+ */
+void
+kern_event_init(struct domain *dp)
+{
+       struct protosw *pr;
+       int i;
+
+       VERIFY(!(dp->dom_flags & DOM_INITIALIZED));
+       VERIFY(dp == systemdomain);
+
+       kev_lck_grp_attr = lck_grp_attr_alloc_init();
+       if (kev_lck_grp_attr == NULL) {
+               panic("%s: lck_grp_attr_alloc_init failed\n", __func__);
+               /* NOTREACHED */
+       }
+
+       kev_lck_grp = lck_grp_alloc_init("Kernel Event Protocol",
+           kev_lck_grp_attr);
+       if (kev_lck_grp == NULL) {
+               panic("%s: lck_grp_alloc_init failed\n", __func__);
+               /* NOTREACHED */
+       }
+
+       kev_lck_attr = lck_attr_alloc_init();
+       if (kev_lck_attr == NULL) {
+               panic("%s: lck_attr_alloc_init failed\n", __func__);
+               /* NOTREACHED */
+       }
+
+       lck_rw_init(kev_rwlock, kev_lck_grp, kev_lck_attr);
+       if (kev_rwlock == NULL) {
+               panic("%s: lck_mtx_alloc_init failed\n", __func__);
+               /* NOTREACHED */
+       }
+
+       for (i = 0, pr = &eventsw[0]; i < event_proto_count; i++, pr++)
+               net_add_proto(pr, dp, 1);
+
+       ev_pcb_zone = zinit(sizeof(struct kern_event_pcb),
+           EVPCB_ZONE_MAX * sizeof(struct kern_event_pcb), 0, EVPCB_ZONE_NAME);
+       if (ev_pcb_zone == NULL) {
+               panic("%s: failed allocating ev_pcb_zone", __func__);
+               /* NOTREACHED */
+       }
+       zone_change(ev_pcb_zone, Z_EXPAND, TRUE);
+       zone_change(ev_pcb_zone, Z_CALLERACCT, TRUE);
 }
 
-/*ARGSUSED*/
 static int
-kqueue_ioctl(__unused struct fileproc *fp, 
-                        __unused u_long com, 
-                        __unused caddr_t data, 
-                        __unused vfs_context_t ctx)
+kev_attach(struct socket *so, __unused int proto, __unused struct proc *p)
 {
-       return (ENOTTY);
+       int error = 0;
+       struct kern_event_pcb *ev_pcb;
+
+       error = soreserve(so, KEV_SNDSPACE, KEV_RECVSPACE);
+       if (error != 0)
+               return (error);
+
+       if ((ev_pcb = (struct kern_event_pcb *)zalloc(ev_pcb_zone)) == NULL) {
+               return (ENOBUFS);
+       }
+       bzero(ev_pcb, sizeof(struct kern_event_pcb));
+       lck_mtx_init(&ev_pcb->evp_mtx, kev_lck_grp, kev_lck_attr);
+
+       ev_pcb->evp_socket = so;
+       ev_pcb->evp_vendor_code_filter = 0xffffffff;
+
+       so->so_pcb = (caddr_t) ev_pcb;
+       lck_rw_lock_exclusive(kev_rwlock);
+       LIST_INSERT_HEAD(&kern_event_head, ev_pcb, evp_link);
+       kevtstat.kes_pcbcount++;
+       kevtstat.kes_gencnt++;
+       lck_rw_done(kev_rwlock);
+
+       return (error);
+}
+
+static void
+kev_delete(struct kern_event_pcb *ev_pcb)
+{
+       VERIFY(ev_pcb != NULL);
+       lck_mtx_destroy(&ev_pcb->evp_mtx, kev_lck_grp);
+       zfree(ev_pcb_zone, ev_pcb);
 }
 
-/*ARGSUSED*/
 static int
-kqueue_select(struct fileproc *fp, int which, void *wql, __unused vfs_context_t ctx)
+kev_detach(struct socket *so)
 {
-       struct kqueue *kq = (struct kqueue *)fp->f_data;
-       struct knote *kn;
-       struct kqtailq inprocessq;
-       int retnum = 0;
-       
-       if (which != FREAD)
-               return 0;
+       struct kern_event_pcb *ev_pcb = (struct kern_event_pcb *) so->so_pcb;
 
-       TAILQ_INIT(&inprocessq);
+       if (ev_pcb != NULL) {
+               soisdisconnected(so);
+               so->so_flags |= SOF_PCBCLEARING;
+       }
+
+       return (0);
+}
+
+/*
+ * For now, kev_vendor_code and mbuf_tags use the same
+ * mechanism.
+ */
+errno_t kev_vendor_code_find(
+       const char      *string,
+       u_int32_t       *out_vendor_code)
+{
+       if (strlen(string) >= KEV_VENDOR_CODE_MAX_STR_LEN) {
+               return (EINVAL);
+       }
+       return (net_str_id_find_internal(string, out_vendor_code,
+           NSI_VENDOR_CODE, 1));
+}
+
+errno_t
+kev_msg_post(struct kev_msg *event_msg)
+{
+       mbuf_tag_id_t min_vendor, max_vendor;
+
+       net_str_id_first_last(&min_vendor, &max_vendor, NSI_VENDOR_CODE);
+
+       if (event_msg == NULL)
+               return (EINVAL);
 
-       kqlock(kq);
        /* 
-        * If this is the first pass, link the wait queue associated with the
-        * the kqueue onto the wait queue set for the select().  Normally we
-        * use selrecord() for this, but it uses the wait queue within the
-        * selinfo structure and we need to use the main one for the kqueue to
-        * catch events from KN_STAYQUEUED sources. So we do the linkage manually.
-        * (The select() call will unlink them when it ends).
+        * Limit third parties to posting events for registered vendor codes
+        * only
         */
-       if (wql != NULL) {
-               thread_t        cur_act = current_thread();
-               struct uthread * ut = get_bsdthread_info(cur_act);
+       if (event_msg->vendor_code < min_vendor ||
+           event_msg->vendor_code > max_vendor) {
+               OSIncrementAtomic64((SInt64 *)&kevtstat.kes_badvendor);
+               return (EINVAL);
+       }
+       return (kev_post_msg(event_msg));
+}
 
-               kq->kq_state |= KQ_SEL;
-               wait_queue_link_noalloc((wait_queue_t)kq->kq_wqs, ut->uu_wqset,
-                                       (wait_queue_link_t)wql);
+int
+kev_post_msg(struct kev_msg *event_msg)
+{
+       struct mbuf *m, *m2;
+       struct kern_event_pcb *ev_pcb;
+       struct kern_event_msg *ev;
+       char *tmp;
+       u_int32_t total_size;
+       int i;
+
+       /* Verify the message is small enough to fit in one mbuf w/o cluster */
+       total_size = KEV_MSG_HEADER_SIZE;
+
+       for (i = 0; i < 5; i++) {
+               if (event_msg->dv[i].data_length == 0)
+                       break;
+               total_size += event_msg->dv[i].data_length;
        }
 
-       if (kqueue_begin_processing(kq) == -1) {
-               kqunlock(kq);
-               return 0;
+       if (total_size > MLEN) {
+               OSIncrementAtomic64((SInt64 *)&kevtstat.kes_toobig);
+               return (EMSGSIZE);
        }
 
-       if (kq->kq_count != 0) {
-               /*
-                * there is something queued - but it might be a
-                * KN_STAYQUEUED knote, which may or may not have
-                * any events pending.  So, we have to walk the
-                * list of knotes to see, and peek at the stay-
-                * queued ones to be really sure.
-                */
-               while ((kn = (struct knote*)TAILQ_FIRST(&kq->kq_head)) != NULL) {
-                       if ((kn->kn_status & KN_STAYQUEUED) == 0) {
-                               retnum = 1;
-                               goto out;
-                       }
+       m = m_get(M_WAIT, MT_DATA);
+       if (m == 0) {
+               OSIncrementAtomic64((SInt64 *)&kevtstat.kes_nomem);
+               return (ENOMEM);
+       }
+       ev = mtod(m, struct kern_event_msg *);
+       total_size = KEV_MSG_HEADER_SIZE;
 
-                       TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
-                       TAILQ_INSERT_TAIL(&inprocessq, kn, kn_tqe);
+       tmp = (char *) &ev->event_data[0];
+       for (i = 0; i < 5; i++) {
+               if (event_msg->dv[i].data_length == 0)
+                       break;
 
-                       if (kqlock2knoteuse(kq, kn)) {
-                               unsigned peek;
+               total_size += event_msg->dv[i].data_length;
+               bcopy(event_msg->dv[i].data_ptr, tmp,
+                   event_msg->dv[i].data_length);
+               tmp += event_msg->dv[i].data_length;
+       }
 
-                               peek = kn->kn_fop->f_peek(kn);
-                               if (knoteuse2kqlock(kq, kn)) {
-                                       if (peek > 0) {
-                                               retnum = 1;
-                                               goto out;
-                                       }
-                               } else {
-                                       retnum = 0;
+       ev->id = ++static_event_id;
+       ev->total_size   = total_size;
+       ev->vendor_code  = event_msg->vendor_code;
+       ev->kev_class    = event_msg->kev_class;
+       ev->kev_subclass = event_msg->kev_subclass;
+       ev->event_code   = event_msg->event_code;
+
+       m->m_len = total_size;
+       lck_rw_lock_shared(kev_rwlock);
+       for (ev_pcb = LIST_FIRST(&kern_event_head);
+           ev_pcb;
+           ev_pcb = LIST_NEXT(ev_pcb, evp_link)) {
+               lck_mtx_lock(&ev_pcb->evp_mtx);
+               if (ev_pcb->evp_socket->so_pcb == NULL) {
+                       lck_mtx_unlock(&ev_pcb->evp_mtx);
+                       continue;
+               }
+               if (ev_pcb->evp_vendor_code_filter != KEV_ANY_VENDOR) {
+                       if (ev_pcb->evp_vendor_code_filter != ev->vendor_code) {
+                               lck_mtx_unlock(&ev_pcb->evp_mtx);
+                               continue;
+                       }
+
+                       if (ev_pcb->evp_class_filter != KEV_ANY_CLASS) {
+                               if (ev_pcb->evp_class_filter != ev->kev_class) {
+                                       lck_mtx_unlock(&ev_pcb->evp_mtx);
+                                       continue;
+                               }
+
+                               if ((ev_pcb->evp_subclass_filter !=
+                                   KEV_ANY_SUBCLASS) &&
+                                   (ev_pcb->evp_subclass_filter !=
+                                   ev->kev_subclass)) {
+                                       lck_mtx_unlock(&ev_pcb->evp_mtx);
+                                       continue;
                                }
-                       } 
+                       }
+               }
+
+               m2 = m_copym(m, 0, m->m_len, M_WAIT);
+               if (m2 == 0) {
+                       OSIncrementAtomic64((SInt64 *)&kevtstat.kes_nomem);
+                       m_free(m);
+                       lck_mtx_unlock(&ev_pcb->evp_mtx);
+                       lck_rw_done(kev_rwlock);
+                       return (ENOMEM);
+               }
+               if (sbappendrecord(&ev_pcb->evp_socket->so_rcv, m2)) {
+                       /*
+                        * We use "m" for the socket stats as it would be
+                        * unsafe to use "m2"
+                        */
+                       so_inc_recv_data_stat(ev_pcb->evp_socket,
+                           1, m->m_len, MBUF_TC_BE);
+
+                       sorwakeup(ev_pcb->evp_socket);
+                       OSIncrementAtomic64((SInt64 *)&kevtstat.kes_posted);
+               } else {
+                       OSIncrementAtomic64((SInt64 *)&kevtstat.kes_fullsock);
                }
+               lck_mtx_unlock(&ev_pcb->evp_mtx);
+       }
+       m_free(m);
+       lck_rw_done(kev_rwlock);
+
+       return (0);
+}
+
+static int
+kev_control(struct socket *so,
+    u_long cmd,
+    caddr_t data,
+    __unused struct ifnet *ifp,
+    __unused struct proc *p)
+{
+       struct kev_request *kev_req = (struct kev_request *) data;
+       struct kern_event_pcb  *ev_pcb;
+       struct kev_vendor_code *kev_vendor;
+       u_int32_t  *id_value = (u_int32_t *) data;
+
+       switch (cmd) {
+               case SIOCGKEVID:
+                       *id_value = static_event_id;
+                       break;
+               case SIOCSKEVFILT:
+                       ev_pcb = (struct kern_event_pcb *) so->so_pcb;
+                       ev_pcb->evp_vendor_code_filter = kev_req->vendor_code;
+                       ev_pcb->evp_class_filter = kev_req->kev_class;
+                       ev_pcb->evp_subclass_filter  = kev_req->kev_subclass;
+                       break;
+               case SIOCGKEVFILT:
+                       ev_pcb = (struct kern_event_pcb *) so->so_pcb;
+                       kev_req->vendor_code = ev_pcb->evp_vendor_code_filter;
+                       kev_req->kev_class   = ev_pcb->evp_class_filter;
+                       kev_req->kev_subclass = ev_pcb->evp_subclass_filter;
+                       break;
+               case SIOCGKEVVENDOR:
+                       kev_vendor = (struct kev_vendor_code *)data;
+                       /* Make sure string is NULL terminated */
+                       kev_vendor->vendor_string[KEV_VENDOR_CODE_MAX_STR_LEN-1] = 0;
+                       return (net_str_id_find_internal(kev_vendor->vendor_string,
+                           &kev_vendor->vendor_code, NSI_VENDOR_CODE, 0));
+               default:
+                       return (ENOTSUP);
        }
 
-out:
-       /* Return knotes to active queue */
-       while ((kn = TAILQ_FIRST(&inprocessq)) != NULL) {
-               TAILQ_REMOVE(&inprocessq, kn, kn_tqe);
-               kn->kn_tq = &kq->kq_head;
-               TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
+       return (0);
+}
+
+int
+kevt_getstat SYSCTL_HANDLER_ARGS
+{
+#pragma unused(oidp, arg1, arg2)
+       int error = 0;
+
+       lck_rw_lock_shared(kev_rwlock);
+
+       if (req->newptr != USER_ADDR_NULL) {
+               error = EPERM;
+               goto done;
+       }
+       if (req->oldptr == USER_ADDR_NULL) {
+               req->oldidx = sizeof(struct kevtstat);
+               goto done;
        }
 
-       kqueue_end_processing(kq);
-       kqunlock(kq);
-       return retnum;
+       error = SYSCTL_OUT(req, &kevtstat,
+           MIN(sizeof(struct kevtstat), req->oldlen));
+done:
+       lck_rw_done(kev_rwlock);
+
+       return (error);
 }
 
-/*
- * kqueue_close -
- */
-/*ARGSUSED*/
-static int
-kqueue_close(struct fileglob *fg, __unused vfs_context_t ctx)
+__private_extern__ int
+kevt_pcblist SYSCTL_HANDLER_ARGS
 {
-       struct kqueue *kq = (struct kqueue *)fg->fg_data;
+#pragma unused(oidp, arg1, arg2)
+       int error = 0;
+       int n, i;
+       struct xsystmgen xsg;
+       void *buf = NULL;
+       size_t item_size = ROUNDUP64(sizeof (struct xkevtpcb)) +
+               ROUNDUP64(sizeof (struct xsocket_n)) +
+               2 * ROUNDUP64(sizeof (struct xsockbuf_n)) +
+               ROUNDUP64(sizeof (struct xsockstat_n));
+       struct kern_event_pcb  *ev_pcb;
 
-       kqueue_dealloc(kq);
-       fg->fg_data = NULL;
-       return (0);
-}
+       buf = _MALLOC(item_size, M_TEMP, M_WAITOK | M_ZERO);
+       if (buf == NULL)
+               return (ENOMEM);
 
-/*ARGSUSED*/
-/*
- * The callers has taken a use-count reference on this kqueue and will donate it
- * to the kqueue we are being added to.  This keeps the kqueue from closing until
- * that relationship is torn down.
- */
-static int
-kqueue_kqfilter(__unused struct fileproc *fp, struct knote *kn, __unused vfs_context_t ctx)
-{
-       struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;
-       struct kqueue *parentkq = kn->kn_kq;
+       lck_rw_lock_shared(kev_rwlock);
 
-       if (parentkq == kq ||
-           kn->kn_filter != EVFILT_READ)
-               return (1);
+       n = kevtstat.kes_pcbcount;
 
+       if (req->oldptr == USER_ADDR_NULL) {
+               req->oldidx = (n + n/8) * item_size;
+               goto done;
+       }
+       if (req->newptr != USER_ADDR_NULL) {
+               error = EPERM;
+               goto done;
+       }
+       bzero(&xsg, sizeof (xsg));
+       xsg.xg_len = sizeof (xsg);
+       xsg.xg_count = n;
+       xsg.xg_gen = kevtstat.kes_gencnt;
+       xsg.xg_sogen = so_gencnt;
+       error = SYSCTL_OUT(req, &xsg, sizeof (xsg));
+       if (error) {
+               goto done;
+       }
        /*
-        * We have to avoid creating a cycle when nesting kqueues
-        * inside another.  Rather than trying to walk the whole
-        * potential DAG of nested kqueues, we just use a simple
-        * ceiling protocol.  When a kqueue is inserted into another,
-        * we check that the (future) parent is not already nested
-        * into another kqueue at a lower level than the potenial
-        * child (because it could indicate a cycle).  If that test
-        * passes, we just mark the nesting levels accordingly.
+        * We are done if there is no pcb
         */
+       if (n == 0) {
+               goto done;
+       }
 
-       kqlock(parentkq);
-       if (parentkq->kq_level > 0 && 
-           parentkq->kq_level < kq->kq_level)
-       {
-               kqunlock(parentkq);
-               return (1);
-       } else {
-               /* set parent level appropriately */
-               if (parentkq->kq_level == 0)
-                       parentkq->kq_level = 2;
-               if (parentkq->kq_level < kq->kq_level + 1)
-                       parentkq->kq_level = kq->kq_level + 1;
-               kqunlock(parentkq);
+       i = 0;
+       for (i = 0, ev_pcb = LIST_FIRST(&kern_event_head);
+           i < n && ev_pcb != NULL;
+           i++, ev_pcb = LIST_NEXT(ev_pcb, evp_link)) {
+               struct xkevtpcb *xk = (struct xkevtpcb *)buf;
+               struct xsocket_n *xso = (struct xsocket_n *)
+                       ADVANCE64(xk, sizeof (*xk));
+               struct xsockbuf_n *xsbrcv = (struct xsockbuf_n *)
+                       ADVANCE64(xso, sizeof (*xso));
+               struct xsockbuf_n *xsbsnd = (struct xsockbuf_n *)
+                       ADVANCE64(xsbrcv, sizeof (*xsbrcv));
+               struct xsockstat_n *xsostats = (struct xsockstat_n *)
+                       ADVANCE64(xsbsnd, sizeof (*xsbsnd));
+
+               bzero(buf, item_size);
+
+               lck_mtx_lock(&ev_pcb->evp_mtx);
+
+               xk->kep_len = sizeof(struct xkevtpcb);
+               xk->kep_kind = XSO_EVT;
+               xk->kep_evtpcb = (uint64_t)VM_KERNEL_ADDRPERM(ev_pcb);
+               xk->kep_vendor_code_filter = ev_pcb->evp_vendor_code_filter;
+               xk->kep_class_filter = ev_pcb->evp_class_filter;
+               xk->kep_subclass_filter = ev_pcb->evp_subclass_filter;
+
+               sotoxsocket_n(ev_pcb->evp_socket, xso);
+               sbtoxsockbuf_n(ev_pcb->evp_socket ?
+                       &ev_pcb->evp_socket->so_rcv : NULL, xsbrcv);
+               sbtoxsockbuf_n(ev_pcb->evp_socket ?
+                       &ev_pcb->evp_socket->so_snd : NULL, xsbsnd);
+               sbtoxsockstat_n(ev_pcb->evp_socket, xsostats);
+
+               lck_mtx_unlock(&ev_pcb->evp_mtx);
+
+               error = SYSCTL_OUT(req, buf, item_size);
+       }
 
-               kn->kn_fop = &kqread_filtops;
-               kqlock(kq);
-               KNOTE_ATTACH(&kq->kq_sel.si_note, kn);
-               /* indicate nesting in child, if needed */
-               if (kq->kq_level == 0)
-                       kq->kq_level = 1;
-               kqunlock(kq);
-               return (0);
+       if (error == 0) {
+               /*
+                * Give the user an updated idea of our state.
+                * If the generation differs from what we told
+                * her before, she knows that something happened
+                * while we were processing this request, and it
+                * might be necessary to retry.
+                */
+               bzero(&xsg, sizeof (xsg));
+               xsg.xg_len = sizeof (xsg);
+               xsg.xg_count = n;
+               xsg.xg_gen = kevtstat.kes_gencnt;
+               xsg.xg_sogen = so_gencnt;
+               error = SYSCTL_OUT(req, &xsg, sizeof (xsg));
+               if (error) {
+                       goto done;
+               }
        }
-}
 
-/*
- * kqueue_drain - called when kq is closed
- */
-/*ARGSUSED*/
-static int
-kqueue_drain(struct fileproc *fp, __unused vfs_context_t ctx)
-{
-       struct kqueue *kq = (struct kqueue *)fp->f_fglob->fg_data;
-       kqlock(kq);
-       kqueue_wakeup(kq, 1);
-       kqunlock(kq);
-       return 0;
+done:
+       lck_rw_done(kev_rwlock);
+
+       return (error);
 }
 
-/*ARGSUSED*/
+#endif /* SOCKETS */
+
+
 int
-kqueue_stat(struct fileproc *fp, void *ub, int isstat64,  __unused vfs_context_t ctx)
+fill_kqueueinfo(struct kqueue *kq, struct kqueue_info * kinfo)
 {
+       struct vinfo_stat * st;
 
-       struct kqueue *kq = (struct kqueue *)fp->f_data;
-       if (isstat64 != 0) {
-               struct stat64 *sb64 = (struct stat64 *)ub;
+       st = &kinfo->kq_stat;
 
-               bzero((void *)sb64, sizeof(*sb64));
-               sb64->st_size = kq->kq_count;
-               if (kq->kq_state & KQ_KEV64)
-                       sb64->st_blksize = sizeof(struct kevent64_s);
-               else
-                       sb64->st_blksize = sizeof(struct kevent);
-               sb64->st_mode = S_IFIFO;
-       } else {
-               struct stat *sb = (struct stat *)ub;
+       st->vst_size = kq->kq_count;
+       if (kq->kq_state & KQ_KEV_QOS)
+               st->vst_blksize = sizeof(struct kevent_qos_s);
+       else if (kq->kq_state & KQ_KEV64)
+               st->vst_blksize = sizeof(struct kevent64_s);
+       else
+               st->vst_blksize = sizeof(struct kevent);
+       st->vst_mode = S_IFIFO;
+       st->vst_ino = (kq->kq_state & KQ_DYNAMIC) ?
+               ((struct kqworkloop *)kq)->kqwl_dynamicid : 0;
 
-               bzero((void *)sb, sizeof(*sb));
-               sb->st_size = kq->kq_count;
-               if (kq->kq_state & KQ_KEV64)
-                       sb->st_blksize = sizeof(struct kevent64_s);
-               else
-                       sb->st_blksize = sizeof(struct kevent);
-               sb->st_mode = S_IFIFO;
-       }
+       /* flags exported to libproc as PROC_KQUEUE_* (sys/proc_info.h) */
+#define PROC_KQUEUE_MASK (KQ_SEL|KQ_SLEEP|KQ_KEV32|KQ_KEV64|KQ_KEV_QOS|KQ_WORKQ|KQ_WORKLOOP)
+       kinfo->kq_state = kq->kq_state & PROC_KQUEUE_MASK;
 
        return (0);
 }
 
-/*
- * Called with the kqueue locked
- */
-static void
-kqueue_wakeup(struct kqueue *kq, int closed)
+static int
+fill_kqueue_dyninfo(struct kqueue *kq, struct kqueue_dyninfo *kqdi)
 {
-       if ((kq->kq_state & (KQ_SLEEP | KQ_SEL)) != 0 || kq->kq_nprocess > 0) {
-               kq->kq_state &= ~(KQ_SLEEP | KQ_SEL);
-               wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, KQ_EVENT, 
-                                     (closed) ? THREAD_INTERRUPTED : THREAD_AWAKENED);
+       struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+       struct kqrequest *kqr = &kqwl->kqwl_request;
+       int err;
+
+       if ((kq->kq_state & KQ_WORKLOOP) == 0) {
+               return EINVAL;
        }
-}
 
-void
-klist_init(struct klist *list)
-{
-       SLIST_INIT(list);
-}
+       if ((err = fill_kqueueinfo(kq, &kqdi->kqdi_info))) {
+               return err;
+       }
 
+       kqwl_req_lock(kqwl);
 
-/*
- * Query/Post each knote in the object's list
- *
- *     The object lock protects the list. It is assumed
- *     that the filter/event routine for the object can
- *     determine that the object is already locked (via
- *     the hint) and not deadlock itself.
- *
- *     The object lock should also hold off pending
- *     detach/drop operations.  But we'll prevent it here
- *     too - just in case.
- */
-void
-knote(struct klist *list, long hint)
-{
-       struct knote *kn;
+       if (kqr->kqr_thread) {
+               kqdi->kqdi_servicer = thread_tid(kqr->kqr_thread);
+       }
 
-       SLIST_FOREACH(kn, list, kn_selnext) {
-               struct kqueue *kq = kn->kn_kq;
+       if (kqwl->kqwl_owner == WL_OWNER_SUSPENDED) {
+               kqdi->kqdi_owner = ~0ull;
+       } else {
+               kqdi->kqdi_owner = thread_tid(kqwl->kqwl_owner);
+       }
 
-               kqlock(kq);
-               if (kqlock2knoteuse(kq, kn)) {
-                       int result;
+       kqdi->kqdi_request_state = kqr->kqr_state;
+       kqdi->kqdi_async_qos = kqr->kqr_qos_index;
+       kqdi->kqdi_events_qos = kqr->kqr_override_index;
+       kqdi->kqdi_sync_waiters = kqr->kqr_dsync_waiters;
+       kqdi->kqdi_sync_waiter_qos = kqr->kqr_dsync_waiters_qos;
 
-                       /* call the event with only a use count */
-                       result = kn->kn_fop->f_event(kn, hint);
+       kqwl_req_unlock(kqwl);
 
-                       /* if its not going away and triggered */
-                       if (knoteuse2kqlock(kq, kn) && result)
-                               knote_activate(kn, 1);
-                       /* lock held again */
-               }
-               kqunlock(kq);
-       }
+       return 0;
 }
 
-/*
- * attach a knote to the specified list.  Return true if this is the first entry.
- * The list is protected by whatever lock the object it is associated with uses.
- */
-int
-knote_attach(struct klist *list, struct knote *kn)
-{
-       int ret = SLIST_EMPTY(list);
-       SLIST_INSERT_HEAD(list, kn, kn_selnext);
-       return ret;
-}
 
-/*
- * detach a knote from the specified list.  Return true if that was the last entry.
- * The list is protected by whatever lock the object it is associated with uses.
- */
-int
-knote_detach(struct klist *list, struct knote *kn)
+void
+knote_markstayactive(struct knote *kn)
 {
-       SLIST_REMOVE(list, kn, knote, kn_selnext);
-       return SLIST_EMPTY(list);
-}
+       struct kqueue *kq = knote_get_kq(kn);
 
-/*
- * For a given knote, link a provided wait queue directly with the kqueue.
- * Wakeups will happen via recursive wait queue support.  But nothing will move 
- * the knote to the active list at wakeup (nothing calls knote()).  Instead,
- * we permanently enqueue them here.
- *
- * kqueue and knote references are held by caller.
- *
- * caller provides the wait queue link structure.
- */
-int
-knote_link_wait_queue(struct knote *kn, struct wait_queue *wq, wait_queue_link_t wql)
-{
-       struct kqueue *kq = kn->kn_kq;
-       kern_return_t kr;
+       kqlock(kq);
+       kn->kn_status |= KN_STAYACTIVE;
 
-       kr = wait_queue_link_noalloc(wq, kq->kq_wqs, wql);
-       if (kr == KERN_SUCCESS) {
-               knote_markstayqueued(kn);
-               return 0;
-       } else {
-               return EINVAL;
+       /*
+        * Making a knote stay active is a property of the knote that must be
+        * established before it is fully attached.
+        */
+       assert(kn->kn_status & KN_ATTACHING);
+
+       /* handle all stayactive knotes on the (appropriate) manager */
+       if (kq->kq_state & KQ_WORKQ) {
+               knote_set_qos_index(kn, KQWQ_QOS_MANAGER);
+       } else if (kq->kq_state & KQ_WORKLOOP) {
+               struct kqworkloop *kqwl = (struct kqworkloop *)kq;
+               kqwl_req_lock(kqwl);
+               assert(kn->kn_req_index && kn->kn_req_index < THREAD_QOS_LAST);
+               kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_STAYACTIVE_QOS,
+                               kn->kn_req_index);
+               kqwl_req_unlock(kqwl);
+               knote_set_qos_index(kn, KQWL_BUCKET_STAYACTIVE);
        }
-}
 
-/*
- * Unlink the provided wait queue from the kqueue associated with a knote.
- * Also remove it from the magic list of directly attached knotes.
- *
- * Note that the unlink may have already happened from the other side, so
- * ignore any failures to unlink and just remove it from the kqueue list.
- *
- * On success, caller is responsible for the link structure
- */
-int
-knote_unlink_wait_queue(struct knote *kn, struct wait_queue *wq, wait_queue_link_t *wqlp)
-{
-       struct kqueue *kq = kn->kn_kq;
-       kern_return_t kr;
-
-       kr = wait_queue_unlink_nofree(wq, kq->kq_wqs, wqlp);
-       kqlock(kq);
-       kn->kn_status &= ~KN_STAYQUEUED;
-       knote_dequeue(kn);
+       knote_activate(kn);
        kqunlock(kq);
-       return (kr != KERN_SUCCESS) ? EINVAL : 0;
 }
 
-/*
- * remove all knotes referencing a specified fd
- *
- * Essentially an inlined knote_remove & knote_drop
- * when we know for sure that the thing is a file
- * 
- * Entered with the proc_fd lock already held.
- * It returns the same way, but may drop it temporarily.
- */
 void
-knote_fdclose(struct proc *p, int fd)
+knote_clearstayactive(struct knote *kn)
 {
-       struct filedesc *fdp = p->p_fd;
-       struct klist *list;
-       struct knote *kn;
-
-       list = &fdp->fd_knlist[fd];
-       while ((kn = SLIST_FIRST(list)) != NULL) {
-               struct kqueue *kq = kn->kn_kq;
-
-               if (kq->kq_p != p)
-                       panic("knote_fdclose: proc mismatch (kq->kq_p=%p != p=%p)", kq->kq_p, p);
-
-               kqlock(kq);
-               proc_fdunlock(p);
-
-               /*
-                * Convert the lock to a drop ref.
-                * If we get it, go ahead and drop it.
-                * Otherwise, we waited for it to
-                * be dropped by the other guy, so
-                * it is safe to move on in the list.
-                */
-               if (kqlock2knotedrop(kq, kn)) {
-                       kn->kn_fop->f_detach(kn);
-                       knote_drop(kn, p);
-               }
-                       
-               proc_fdlock(p);
-
-               /* the fd tables may have changed - start over */
-               list = &fdp->fd_knlist[fd];
-       }
+       kqlock(knote_get_kq(kn));
+       kn->kn_status &= ~KN_STAYACTIVE;
+       knote_deactivate(kn);
+       kqunlock(knote_get_kq(kn));
 }
 
-/* proc_fdlock held on entry (and exit) */
-static int
-knote_fdpattach(struct knote *kn, struct filedesc *fdp, struct proc *p)
+static unsigned long
+kevent_extinfo_emit(struct kqueue *kq, struct knote *kn, struct kevent_extinfo *buf,
+               unsigned long buflen, unsigned long nknotes)
 {
-       struct klist *list = NULL;
+       for (; kn; kn = SLIST_NEXT(kn, kn_link)) {
+               if (kq == knote_get_kq(kn)) {
+                       if (nknotes < buflen) {
+                               struct kevent_extinfo *info = &buf[nknotes];
+                               struct kevent_internal_s *kevp = &kn->kn_kevent;
 
-       if (! kn->kn_fop->f_isfd) {
-               if (fdp->fd_knhashmask == 0)
-                       fdp->fd_knhash = hashinit(CONFIG_KN_HASHSIZE, M_KQUEUE,
-                           &fdp->fd_knhashmask);
-               list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
-       } else {
-               if ((u_int)fdp->fd_knlistsize <= kn->kn_id) {
-                       u_int size = 0;
+                               kqlock(kq);
 
-                       if (kn->kn_id >= (uint64_t)p->p_rlimit[RLIMIT_NOFILE].rlim_cur 
-                           || kn->kn_id >= (uint64_t)maxfiles)
-                               return (EINVAL);
-               
-                       /* have to grow the fd_knlist */
-                       size = fdp->fd_knlistsize;
-                       while (size <= kn->kn_id)
-                               size += KQEXTENT;
+                               info->kqext_kev = (struct kevent_qos_s){
+                                       .ident = kevp->ident,
+                                       .filter = kevp->filter,
+                                       .flags = kevp->flags,
+                                       .fflags = kevp->fflags,
+                                       .data = (int64_t)kevp->data,
+                                       .udata = kevp->udata,
+                                       .ext[0] = kevp->ext[0],
+                                       .ext[1] = kevp->ext[1],
+                                       .ext[2] = kevp->ext[2],
+                                       .ext[3] = kevp->ext[3],
+                                       .qos = kn->kn_req_index,
+                               };
+                               info->kqext_sdata = kn->kn_sdata;
+                               info->kqext_status = kn->kn_status;
+                               info->kqext_sfflags = kn->kn_sfflags;
 
-                       if (size >= (UINT_MAX/sizeof(struct klist *)))
-                               return (EINVAL);
+                               kqunlock(kq);
+                       }
 
-                       MALLOC(list, struct klist *,
-                              size * sizeof(struct klist *), M_KQUEUE, M_WAITOK);
-                       if (list == NULL)
-                               return (ENOMEM);
-                       
-                       bcopy((caddr_t)fdp->fd_knlist, (caddr_t)list,
-                             fdp->fd_knlistsize * sizeof(struct klist *));
-                       bzero((caddr_t)list +
-                             fdp->fd_knlistsize * sizeof(struct klist *),
-                             (size - fdp->fd_knlistsize) * sizeof(struct klist *));
-                       FREE(fdp->fd_knlist, M_KQUEUE);
-                       fdp->fd_knlist = list;
-                       fdp->fd_knlistsize = size;
+                       /* we return total number of knotes, which may be more than requested */
+                       nknotes++;
                }
-               list = &fdp->fd_knlist[kn->kn_id];
        }
-       SLIST_INSERT_HEAD(list, kn, kn_link);
-       return (0);
-}
-
 
+       return nknotes;
+}
 
-/*
- * should be called at spl == 0, since we don't want to hold spl
- * while calling fdrop and free.
- */
-static void
-knote_drop(struct knote *kn, __unused struct proc *ctxp)
+int
+kevent_copyout_proc_dynkqids(void *proc, user_addr_t ubuf, uint32_t ubufsize,
+               int32_t *nkqueues_out)
 {
-       struct kqueue *kq = kn->kn_kq;
-       struct proc *p = kq->kq_p;
-        struct filedesc *fdp = p->p_fd;
-       struct klist *list;
-       int needswakeup;
+       proc_t p = (proc_t)proc;
+       struct filedesc *fdp = p->p_fd;
+       unsigned int nkqueues = 0;
+       unsigned long ubuflen = ubufsize / sizeof(kqueue_id_t);
+       size_t buflen, bufsize;
+       kqueue_id_t *kq_ids = NULL;
+       int err = 0;
 
-       proc_fdlock(p);
-       if (kn->kn_fop->f_isfd)
-               list = &fdp->fd_knlist[kn->kn_id];
-       else
-               list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
+       assert(p != NULL);
 
-       SLIST_REMOVE(list, kn, knote, kn_link);
-       kqlock(kq);
-       knote_dequeue(kn);
-       needswakeup = (kn->kn_status & KN_USEWAIT);
-       kqunlock(kq);
-       proc_fdunlock(p);
+       if (ubuf == USER_ADDR_NULL && ubufsize != 0) {
+               err = EINVAL;
+               goto out;
+       }
 
-       if (needswakeup)
-               wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_AWAKENED);
+       buflen = min(ubuflen, PROC_PIDDYNKQUEUES_MAX);
 
-       if (kn->kn_fop->f_isfd)
-               fp_drop(p, kn->kn_id, kn->kn_fp, 0);
+       if (ubuflen != 0) {
+               if (os_mul_overflow(sizeof(kqueue_id_t), buflen, &bufsize)) {
+                       err = ERANGE;
+                       goto out;
+               }
+               kq_ids = kalloc(bufsize);
+               assert(kq_ids != NULL);
+       }
 
-       knote_free(kn);
-}
+       kqhash_lock(p);
 
-/* called with kqueue lock held */
-static void
-knote_activate(struct knote *kn, int propagate)
-{
-       struct kqueue *kq = kn->kn_kq;
+       if (fdp->fd_kqhashmask > 0) {
+               for (uint32_t i = 0; i < fdp->fd_kqhashmask + 1; i++) {
+                       struct kqworkloop *kqwl;
 
-       kn->kn_status |= KN_ACTIVE;
-       knote_enqueue(kn);
-       kqueue_wakeup(kq, 0);
+                       SLIST_FOREACH(kqwl, &fdp->fd_kqhash[i], kqwl_hashlink) {
+                               /* report the number of kqueues, even if they don't all fit */
+                               if (nkqueues < buflen) {
+                                       kq_ids[nkqueues] = kqwl->kqwl_dynamicid;
+                               }
+                               nkqueues++;
+                       }
+               }
+       }
 
-       /* this is a real event: wake up the parent kq, too */
-       if (propagate)
-               KNOTE(&kq->kq_sel.si_note, 0);
-}
+       kqhash_unlock(p);
 
-/* called with kqueue lock held */
-static void
-knote_deactivate(struct knote *kn)
-{      
-       kn->kn_status &= ~KN_ACTIVE;
-       knote_dequeue(kn);
-}
+       if (kq_ids) {
+               size_t copysize;
+               if (os_mul_overflow(sizeof(kqueue_id_t), min(ubuflen, nkqueues), &copysize)) {
+                       err = ERANGE;
+                       goto out;
+               }
 
-/* called with kqueue lock held */
-static void
-knote_enqueue(struct knote *kn)
-{
-       if ((kn->kn_status & (KN_QUEUED | KN_STAYQUEUED)) == KN_STAYQUEUED ||
-           (kn->kn_status & (KN_QUEUED | KN_STAYQUEUED | KN_DISABLED)) == 0) {
-               struct kqtailq *tq = kn->kn_tq;
-               struct kqueue *kq = kn->kn_kq;
+               assert(ubufsize >= copysize);
+               err = copyout(kq_ids, ubuf, copysize);
+       }
 
-               TAILQ_INSERT_TAIL(tq, kn, kn_tqe); 
-               kn->kn_status |= KN_QUEUED;
-               kq->kq_count++;
+out:
+       if (kq_ids) {
+               kfree(kq_ids, bufsize);
        }
+
+       if (!err) {
+               *nkqueues_out = (int)min(nkqueues, PROC_PIDDYNKQUEUES_MAX);
+       }
+       return err;
 }
 
-/* called with kqueue lock held */
-static void
-knote_dequeue(struct knote *kn)
+int
+kevent_copyout_dynkqinfo(void *proc, kqueue_id_t kq_id, user_addr_t ubuf,
+               uint32_t ubufsize, int32_t *size_out)
 {
-       struct kqueue *kq = kn->kn_kq;
+       proc_t p = (proc_t)proc;
+       struct kqueue *kq;
+       int err = 0;
+       struct kqueue_dyninfo kqdi = { };
+
+       assert(p != NULL);
 
-       if ((kn->kn_status & (KN_QUEUED | KN_STAYQUEUED)) == KN_QUEUED) {
-               struct kqtailq *tq = kn->kn_tq;
+       if (ubufsize < sizeof(struct kqueue_info)) {
+               return ENOBUFS;
+       }
+
+       kqhash_lock(p);
+       kq = kqueue_hash_lookup(p, kq_id);
+       if (!kq) {
+               kqhash_unlock(p);
+               return ESRCH;
+       }
+       kqueue_retain(kq);
+       kqhash_unlock(p);
 
-               TAILQ_REMOVE(tq, kn, kn_tqe); 
-               kn->kn_tq = &kq->kq_head;
-               kn->kn_status &= ~KN_QUEUED;
-               kq->kq_count--;
+       /*
+        * backward compatibility: allow the argument to this call to only be
+        * a struct kqueue_info
+        */
+       if (ubufsize >= sizeof(struct kqueue_dyninfo)) {
+               ubufsize = sizeof(struct kqueue_dyninfo);
+               err = fill_kqueue_dyninfo(kq, &kqdi);
+       } else {
+               ubufsize = sizeof(struct kqueue_info);
+               err = fill_kqueueinfo(kq, &kqdi.kqdi_info);
        }
+       if (err == 0 && (err = copyout(&kqdi, ubuf, ubufsize)) == 0) {
+               *size_out = ubufsize;
+       }
+       kqueue_release_last(p, kq);
+       return err;
 }
 
-void
-knote_init(void)
+int
+kevent_copyout_dynkqextinfo(void *proc, kqueue_id_t kq_id, user_addr_t ubuf,
+               uint32_t ubufsize, int32_t *nknotes_out)
 {
-       knote_zone = zinit(sizeof(struct knote), 8192*sizeof(struct knote), 8192, "knote zone");
-
-       /* allocate kq lock group attribute and group */
-       kq_lck_grp_attr= lck_grp_attr_alloc_init();
+       proc_t p = (proc_t)proc;
+       struct kqueue *kq;
+       int err;
 
-       kq_lck_grp = lck_grp_alloc_init("kqueue",  kq_lck_grp_attr);
+       assert(p != NULL);
 
-       /* Allocate kq lock attribute */
-       kq_lck_attr = lck_attr_alloc_init();
+       kqhash_lock(p);
+       kq = kqueue_hash_lookup(p, kq_id);
+       if (!kq) {
+               kqhash_unlock(p);
+               return ESRCH;
+       }
+       kqueue_retain(kq);
+       kqhash_unlock(p);
 
-       /* Initialize the timer filter lock */
-       lck_mtx_init(&_filt_timerlock, kq_lck_grp, kq_lck_attr);
-       
-#if VM_PRESSURE_EVENTS
-       /* Initialize the vm pressure list lock */
-       vm_pressure_init(kq_lck_grp, kq_lck_attr);
-#endif
+       err = pid_kqueue_extinfo(p, kq, ubuf, ubufsize, nknotes_out);
+       kqueue_release_last(p, kq);
+       return err;
 }
-SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_ANY, knote_init, NULL)
 
-static struct knote *
-knote_alloc(void)
+int
+pid_kqueue_extinfo(proc_t p, struct kqueue *kq, user_addr_t ubuf,
+               uint32_t bufsize, int32_t *retval)
 {
-       return ((struct knote *)zalloc(knote_zone));
-}
+       struct knote *kn;
+       int i;
+       int err = 0;
+       struct filedesc *fdp = p->p_fd;
+       unsigned long nknotes = 0;
+       unsigned long buflen = bufsize / sizeof(struct kevent_extinfo);
+       struct kevent_extinfo *kqext = NULL;
 
-static void
-knote_free(struct knote *kn)
-{
-       zfree(knote_zone, kn);
-}
+       /* arbitrary upper limit to cap kernel memory usage, copyout size, etc. */
+       buflen = min(buflen, PROC_PIDFDKQUEUE_KNOTES_MAX);
 
-#if SOCKETS
-#include <sys/param.h>
-#include <sys/socket.h>
-#include <sys/protosw.h>
-#include <sys/domain.h>
-#include <sys/mbuf.h>
-#include <sys/kern_event.h>
-#include <sys/malloc.h>
-#include <sys/sys_domain.h>
-#include <sys/syslog.h>
+       kqext = kalloc(buflen * sizeof(struct kevent_extinfo));
+       if (kqext == NULL) {
+               err = ENOMEM;
+               goto out;
+       }
+       bzero(kqext, buflen * sizeof(struct kevent_extinfo));
 
+       proc_fdlock(p);
+       for (i = 0; i < fdp->fd_knlistsize; i++) {
+               kn = SLIST_FIRST(&fdp->fd_knlist[i]);
+               nknotes = kevent_extinfo_emit(kq, kn, kqext, buflen, nknotes);
+       }
+       proc_fdunlock(p);
 
-static int kev_attach(struct socket *so, int proto, struct proc *p);
-static int kev_detach(struct socket *so);
-static int kev_control(struct socket *so, u_long cmd, caddr_t data, struct ifnet *ifp, struct proc *p);
-
-struct pr_usrreqs event_usrreqs = {
-     pru_abort_notsupp, pru_accept_notsupp, kev_attach, pru_bind_notsupp, pru_connect_notsupp,
-     pru_connect2_notsupp, kev_control, kev_detach, pru_disconnect_notsupp,
-     pru_listen_notsupp, pru_peeraddr_notsupp, pru_rcvd_notsupp, pru_rcvoob_notsupp,
-     pru_send_notsupp, pru_sense_null, pru_shutdown_notsupp, pru_sockaddr_notsupp,
-     pru_sosend_notsupp, soreceive, pru_sopoll_notsupp
-};
+       if (fdp->fd_knhashmask != 0) {
+               for (i = 0; i < (int)fdp->fd_knhashmask + 1; i++) {
+                       kqhash_lock(p);
+                       kn = SLIST_FIRST(&fdp->fd_knhash[i]);
+                       nknotes = kevent_extinfo_emit(kq, kn, kqext, buflen, nknotes);
+                       kqhash_unlock(p);
+               }
+       }
 
-struct protosw eventsw[] = {
-     {
-         .pr_type = SOCK_RAW,
-         .pr_domain = &systemdomain,
-         .pr_protocol = SYSPROTO_EVENT,
-         .pr_flags = PR_ATOMIC,
-         .pr_usrreqs = &event_usrreqs,
-     }
-};
+       assert(bufsize >= sizeof(struct kevent_extinfo) * min(buflen, nknotes));
+       err = copyout(kqext, ubuf, sizeof(struct kevent_extinfo) * min(buflen, nknotes));
 
-static
-struct kern_event_head kern_event_head;
+ out:
+       if (kqext) {
+               kfree(kqext, buflen * sizeof(struct kevent_extinfo));
+               kqext = NULL;
+       }
 
-static u_int32_t static_event_id = 0;
-struct domain *sysdom = &systemdomain;
-static lck_mtx_t *sys_mtx;
+       if (!err) {
+               *retval = min(nknotes, PROC_PIDFDKQUEUE_KNOTES_MAX);
+       }
+       return err;
+}
 
-/*
- * Install the protosw's for the NKE manager.  Invoked at
- *  extension load time
- */
-int
-kern_event_init(void)
+static unsigned int
+klist_copy_udata(struct klist *list, uint64_t *buf,
+               unsigned int buflen, unsigned int nknotes)
 {
-    int retval;
-
-    if ((retval = net_add_proto(eventsw, &systemdomain)) != 0) {
-           log(LOG_WARNING, "Can't install kernel events protocol (%d)\n", retval);
-            return(retval);
+       struct kevent_internal_s *kev;
+       struct knote *kn;
+       SLIST_FOREACH(kn, list, kn_link) {
+               if (nknotes < buflen) {
+                       struct kqueue *kq = knote_get_kq(kn);
+                       kqlock(kq);
+                       kev = &(kn->kn_kevent);
+                       buf[nknotes] = kev->udata;
+                       kqunlock(kq);
+               }
+               /* we return total number of knotes, which may be more than requested */
+               nknotes++;
        }
-   
-    /*
-     * Use the domain mutex for all system event sockets
-     */ 
-    sys_mtx = sysdom->dom_mtx;
-       
-    return(KERN_SUCCESS);
+
+       return nknotes;
 }
 
-static int
-kev_attach(struct socket *so, __unused int proto, __unused struct proc *p)
+static unsigned int
+kqlist_copy_dynamicids(__assert_only proc_t p, struct kqlist *list,
+               uint64_t *buf, unsigned int buflen, unsigned int nids)
 {
-     int error;
-     struct kern_event_pcb  *ev_pcb;
+       kqhash_lock_held(p);
+       struct kqworkloop *kqwl;
+       SLIST_FOREACH(kqwl, list, kqwl_hashlink) {
+               if (nids < buflen) {
+                       buf[nids] = kqwl->kqwl_dynamicid;
+               }
+               nids++;
+       }
+       return nids;
+}
 
-     error = soreserve(so, KEV_SNDSPACE, KEV_RECVSPACE);
-     if (error)
-          return error;
+int
+kevent_proc_copy_uptrs(void *proc, uint64_t *buf, int bufsize)
+{
+       proc_t p = (proc_t)proc;
+       struct filedesc *fdp = p->p_fd;
+       unsigned int nuptrs = 0;
+       unsigned long buflen = bufsize / sizeof(uint64_t);
 
-     MALLOC(ev_pcb, struct kern_event_pcb *, sizeof(struct kern_event_pcb), M_PCB, M_WAITOK);
-     if (ev_pcb == 0)
-         return ENOBUFS;
+       if (buflen > 0) {
+               assert(buf != NULL);
+       }
 
-     ev_pcb->ev_socket = so;
-     ev_pcb->vendor_code_filter = 0xffffffff;
+       proc_fdlock(p);
+       for (int i = 0; i < fdp->fd_knlistsize; i++) {
+               nuptrs = klist_copy_udata(&fdp->fd_knlist[i], buf, buflen, nuptrs);
+       }
+       knhash_lock(p);
+       proc_fdunlock(p);
+       if (fdp->fd_knhashmask != 0) {
+               for (int i = 0; i < (int)fdp->fd_knhashmask + 1; i++) {
+                       nuptrs = klist_copy_udata(&fdp->fd_knhash[i], buf, buflen, nuptrs);
+               }
+       }
+       knhash_unlock(p);
 
-     so->so_pcb = (caddr_t) ev_pcb;
-     lck_mtx_lock(sys_mtx);
-     LIST_INSERT_HEAD(&kern_event_head, ev_pcb, ev_link);
-     lck_mtx_unlock(sys_mtx);
+       kqhash_lock(p);
+       if (fdp->fd_kqhashmask != 0) {
+               for (int i = 0; i < (int)fdp->fd_kqhashmask + 1; i++) {
+                       nuptrs = kqlist_copy_dynamicids(p, &fdp->fd_kqhash[i], buf, buflen,
+                                       nuptrs);
+               }
+       }
+       kqhash_unlock(p);
 
-     return 0;
+       return (int)nuptrs;
 }
 
-
-static int
-kev_detach(struct socket *so)
+static void
+kevent_redrive_proc_thread_request(proc_t p)
 {
-     struct kern_event_pcb *ev_pcb = (struct kern_event_pcb *) so->so_pcb;
+       __assert_only int ret;
+       ret = (*pthread_functions->workq_threadreq)(p, NULL, WORKQ_THREADREQ_REDRIVE, 0, 0);
+       assert(ret == 0 || ret == ECANCELED);
+}
 
-     if (ev_pcb != 0) {
-               LIST_REMOVE(ev_pcb, ev_link);
-               FREE(ev_pcb, M_PCB);
-               so->so_pcb = 0;
-               so->so_flags |= SOF_PCBCLEARING;
-     }
+static void
+kevent_set_return_to_kernel_user_tsd(proc_t p, thread_t thread)
+{
+       uint64_t ast_addr;
+       bool proc_is_64bit = !!(p->p_flag & P_LP64);
+       size_t user_addr_size = proc_is_64bit ? 8 : 4;
+       uint32_t ast_flags32 = 0;
+       uint64_t ast_flags64 = 0;
+       struct uthread *ut = get_bsdthread_info(thread);
+
+       if (ut->uu_kqueue_bound != NULL) {
+               if (ut->uu_kqueue_flags & KEVENT_FLAG_WORKLOOP) {
+                       ast_flags64 |= R2K_WORKLOOP_PENDING_EVENTS;
+               } else if (ut->uu_kqueue_flags & KEVENT_FLAG_WORKQ) {
+                       ast_flags64 |= R2K_WORKQ_PENDING_EVENTS;
+               }
+       }
 
-     return 0;
-}
+       if (ast_flags64 == 0) {
+               return;
+       }
 
-/*
- * For now, kev_vendor_code and mbuf_tags use the same
- * mechanism.
- */
+       if (!(p->p_flag & P_LP64)) {
+               ast_flags32 = (uint32_t)ast_flags64;
+               assert(ast_flags64 < 0x100000000ull);
+       }
 
-errno_t kev_vendor_code_find(
-       const char      *string,
-       u_int32_t       *out_vendor_code)
-{
-       if (strlen(string) >= KEV_VENDOR_CODE_MAX_STR_LEN) {
-               return EINVAL;
+       ast_addr = thread_rettokern_addr(thread);
+       if (ast_addr == 0) {
+               return;
        }
-       return net_str_id_find_internal(string, out_vendor_code, NSI_VENDOR_CODE, 1);
-}
 
-errno_t  kev_msg_post(struct kev_msg *event_msg)
-{
-       mbuf_tag_id_t   min_vendor, max_vendor;
-       
-       net_str_id_first_last(&min_vendor, &max_vendor, NSI_VENDOR_CODE);
-       
-       if (event_msg == NULL)
-               return EINVAL;
-       
-       /* Limit third parties to posting events for registered vendor codes only */
-       if (event_msg->vendor_code < min_vendor ||
-               event_msg->vendor_code > max_vendor)
-       {
-               return EINVAL;
+       if (copyout((proc_is_64bit ? (void *)&ast_flags64 : (void *)&ast_flags32),
+                   (user_addr_t)ast_addr,
+                   user_addr_size) != 0) {
+               printf("pid %d (tid:%llu): copyout of return_to_kernel ast flags failed with "
+                      "ast_addr = %llu\n", p->p_pid, thread_tid(current_thread()), ast_addr);
        }
-       
-       return kev_post_msg(event_msg);
 }
-       
 
-int  kev_post_msg(struct kev_msg *event_msg)
+void
+kevent_ast(thread_t thread, uint16_t bits)
 {
-     struct mbuf *m, *m2;
-     struct kern_event_pcb  *ev_pcb;
-     struct kern_event_msg  *ev;
-     char              *tmp;
-     u_int32_t     total_size;
-     int               i;
+       proc_t p = current_proc();
 
-       /* Verify the message is small enough to fit in one mbuf w/o cluster */
-       total_size = KEV_MSG_HEADER_SIZE;
-       
-       for (i = 0; i < 5; i++) {
-               if (event_msg->dv[i].data_length == 0)
-                       break;
-               total_size += event_msg->dv[i].data_length;
+       if (bits & AST_KEVENT_REDRIVE_THREADREQ) {
+               kevent_redrive_proc_thread_request(p);
        }
-       
-       if (total_size > MLEN) {
-               return EMSGSIZE;
-       }
-
-     m = m_get(M_DONTWAIT, MT_DATA);
-     if (m == 0)
-         return ENOBUFS;
-
-     ev = mtod(m, struct kern_event_msg *);
-     total_size = KEV_MSG_HEADER_SIZE;
-
-     tmp = (char *) &ev->event_data[0];
-     for (i = 0; i < 5; i++) {
-         if (event_msg->dv[i].data_length == 0)
-              break;
-
-         total_size += event_msg->dv[i].data_length;
-         bcopy(event_msg->dv[i].data_ptr, tmp, 
-               event_msg->dv[i].data_length);
-         tmp += event_msg->dv[i].data_length;
-     }
-
-     ev->id = ++static_event_id;
-     ev->total_size   = total_size;
-     ev->vendor_code  = event_msg->vendor_code;
-     ev->kev_class    = event_msg->kev_class;
-     ev->kev_subclass = event_msg->kev_subclass;
-     ev->event_code   = event_msg->event_code;
-
-     m->m_len = total_size;
-     lck_mtx_lock(sys_mtx);
-     for (ev_pcb = LIST_FIRST(&kern_event_head); 
-         ev_pcb; 
-         ev_pcb = LIST_NEXT(ev_pcb, ev_link)) {
-
-         if (ev_pcb->vendor_code_filter != KEV_ANY_VENDOR) {
-              if (ev_pcb->vendor_code_filter != ev->vendor_code)
-                   continue;
-
-              if (ev_pcb->class_filter != KEV_ANY_CLASS) {
-                   if (ev_pcb->class_filter != ev->kev_class)
-                        continue;
-
-                   if ((ev_pcb->subclass_filter != KEV_ANY_SUBCLASS) &&
-                       (ev_pcb->subclass_filter != ev->kev_subclass))
-                        continue;
-              }
-         }
-
-         m2 = m_copym(m, 0, m->m_len, M_NOWAIT);
-         if (m2 == 0) {
-              m_free(m);
-                  lck_mtx_unlock(sys_mtx);
-              return ENOBUFS;
-         }
-         /* the socket is already locked because we hold the sys_mtx here */
-         if (sbappendrecord(&ev_pcb->ev_socket->so_rcv, m2))
-                 sorwakeup(ev_pcb->ev_socket);
-     }
-
-     m_free(m);
-     lck_mtx_unlock(sys_mtx);
-     return 0;
-}
-
-static int
-kev_control(struct socket *so, 
-                       u_long cmd, 
-                       caddr_t data, 
-                       __unused struct ifnet *ifp, 
-                       __unused struct proc *p)
-{
-       struct kev_request *kev_req = (struct kev_request *) data;
-       struct kern_event_pcb  *ev_pcb;
-       struct kev_vendor_code *kev_vendor;
-       u_int32_t  *id_value = (u_int32_t *) data;
-       
-       
-       switch (cmd) {
-               
-               case SIOCGKEVID:
-                       *id_value = static_event_id;
-                       break;
-               
-               case SIOCSKEVFILT:
-                       ev_pcb = (struct kern_event_pcb *) so->so_pcb;
-                       ev_pcb->vendor_code_filter = kev_req->vendor_code;
-                       ev_pcb->class_filter     = kev_req->kev_class;
-                       ev_pcb->subclass_filter  = kev_req->kev_subclass;
-                       break;
-               
-               case SIOCGKEVFILT:
-                       ev_pcb = (struct kern_event_pcb *) so->so_pcb;
-                       kev_req->vendor_code = ev_pcb->vendor_code_filter;
-                       kev_req->kev_class   = ev_pcb->class_filter;
-                       kev_req->kev_subclass = ev_pcb->subclass_filter;
-                       break;
-               
-               case SIOCGKEVVENDOR:
-                       kev_vendor = (struct kev_vendor_code*)data;
-                       
-                       /* Make sure string is NULL terminated */
-                       kev_vendor->vendor_string[KEV_VENDOR_CODE_MAX_STR_LEN-1] = 0;
-               
-                       return net_str_id_find_internal(kev_vendor->vendor_string, 
-                                       &kev_vendor->vendor_code, NSI_VENDOR_CODE, 0);
-               
-               default:
-                       return ENOTSUP;
+       if (bits & AST_KEVENT_RETURN_TO_KERNEL) {
+               kevent_set_return_to_kernel_user_tsd(p, thread);
        }
-       
-       return 0;
 }
 
-#endif /* SOCKETS */
+#if DEVELOPMENT || DEBUG
 
+#define KEVENT_SYSCTL_BOUND_ID 1
 
-int
-fill_kqueueinfo(struct kqueue *kq, struct kqueue_info * kinfo)
+static int
+kevent_sysctl SYSCTL_HANDLER_ARGS
 {
-       struct vinfo_stat * st;
+#pragma unused(oidp, arg2)
+       uintptr_t type = (uintptr_t)arg1;
+       uint64_t bound_id = 0;
+       struct uthread *ut;
+       struct kqueue *kq;
 
-       /* No need for the funnel as fd is kept alive */
-       
-       st = &kinfo->kq_stat;
+       if (type != KEVENT_SYSCTL_BOUND_ID) {
+               return EINVAL;
+       }
 
-       st->vst_size = kq->kq_count;
-       if (kq->kq_state & KQ_KEV64)
-               st->vst_blksize = sizeof(struct kevent64_s);
-       else
-               st->vst_blksize = sizeof(struct kevent);
-       st->vst_mode = S_IFIFO;
-       if (kq->kq_state & KQ_SEL)
-               kinfo->kq_state |=  PROC_KQUEUE_SELECT;
-       if (kq->kq_state & KQ_SLEEP)
-               kinfo->kq_state |= PROC_KQUEUE_SLEEP;
+       if (req->newptr) {
+               return EINVAL;
+       }
 
-       return(0);
-}
+       ut = get_bsdthread_info(current_thread());
+       if (!ut) {
+               return EFAULT;
+       }
 
+       kq = ut->uu_kqueue_bound;
+       if (kq) {
+               if (kq->kq_state & KQ_WORKLOOP) {
+                       bound_id = ((struct kqworkloop *)kq)->kqwl_dynamicid;
+               } else if (kq->kq_state & KQ_WORKQ) {
+                       bound_id = -1;
+               }
+       }
 
-void
-knote_markstayqueued(struct knote *kn)
-{
-       kqlock(kn->kn_kq);
-       kn->kn_status |= KN_STAYQUEUED;
-       knote_enqueue(kn);
-       kqunlock(kn->kn_kq);
+       return sysctl_io_number(req, bound_id, sizeof(bound_id), NULL, NULL);
 }
+
+SYSCTL_NODE(_kern, OID_AUTO, kevent, CTLFLAG_RW | CTLFLAG_LOCKED, 0,
+               "kevent information");
+
+SYSCTL_PROC(_kern_kevent, OID_AUTO, bound_id,
+               CTLTYPE_QUAD | CTLFLAG_RD | CTLFLAG_LOCKED | CTLFLAG_MASKED,
+               (void *)KEVENT_SYSCTL_BOUND_ID,
+               sizeof(kqueue_id_t), kevent_sysctl, "Q",
+               "get the ID of the bound kqueue");
+
+#endif /* DEVELOPMENT || DEBUG */