xnu-4903.241.1.tar.gz

[apple/xnu.git] / bsd / kern / kern_event.c

/*
 * 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
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * 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,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * 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@
 *
 */
/*-
 * Copyright (c) 1999,2000,2001 Jonathan Lemon <jlemon@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 *      @(#)kern_event.c       1.0 (3/31/2000)
 */
#include <stdint.h>
#include <machine/atomic.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/malloc.h>
#include <sys/unistd.h>
#include <sys/file_internal.h>
#include <sys/fcntl.h>
#include <sys/select.h>
#include <sys/queue.h>
#include <sys/event.h>
#include <sys/eventvar.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/uio.h>
#include <sys/sysproto.h>
#include <sys/user.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 <pexpert/pexpert.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 <pthread/priority_private.h>
#include <pthread/workqueue_syscalls.h>
#include <pthread/workqueue_internal.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 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))

MALLOC_DEFINE(M_KQUEUE, "kqueue", "memory for kqueue system");

#define KQ_EVENT        NO_EVENT64

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 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 int kevent_register_wait_prepare(struct knote *kn, struct kevent_internal_s *kev);
static void kevent_register_wait_block(struct turnstile *ts, thread_t handoff_thread,
                struct knote_lock_ctx *knlc, thread_continue_t cont,
                struct _kevent_register *cont_args) __dead2;
static void kevent_register_wait_return(struct _kevent_register *cont_args) __dead2;
static void kevent_register_wait_cleanup(struct knote *kn);
static inline void kqueue_release_last(struct proc *p, kqueue_t kqu);
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);
static int kqueue_queue_empty(struct kqueue *kq, kq_index_t qos_index);

static struct kqtailq *kqueue_get_suppressed_queue(kqueue_t kq, struct knote *kn);
static void kqueue_threadreq_initiate(struct kqueue *kq, struct kqrequest *kqr, kq_index_t qos, int flags);

static void kqworkq_update_override(struct kqworkq *kqwq, struct knote *kn, kq_index_t qos);
static void kqworkq_unbind(proc_t p, struct kqrequest *kqr);
static thread_qos_t kqworkq_unbind_locked(struct kqworkq *kqwq, struct kqrequest *kqr, thread_t thread);
static struct kqrequest *kqworkq_get_request(struct kqworkq *kqwq, kq_index_t qos_index);

static void kqworkloop_update_override(struct kqworkloop *kqwl, kq_index_t override_index);
static void kqworkloop_unbind(proc_t p, struct kqworkloop *kwql);
static thread_qos_t kqworkloop_unbind_locked(struct kqworkloop *kwql, thread_t thread);
static kq_index_t kqworkloop_owner_override(struct kqworkloop *kqwl);
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,
        KQWL_UTQ_UNBINDING, /* attempt to rebind */
        KQWL_UTQ_PARKING,
        /*
         * 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 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_QOS_INDEX,
        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);
static int kqworkloop_end_processing(struct kqworkloop *kqwl, int flags, int kevent_flags);

static int knote_process(struct knote *kn, kevent_callback_t callback, void *callback_data,
                         struct filt_process_s *process_data);

static int kq_add_knote(struct kqueue *kq, struct knote *kn,
                struct knote_lock_ctx *knlc, struct proc *p);
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 knote_drop(struct kqueue *kq, struct knote *kn, struct knote_lock_ctx *knlc);
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 bool knote_should_apply_qos_override(struct kqueue *kq, struct knote *kn,
                int result, thread_qos_t *qos_out);
static void knote_apply_qos_override(struct knote *kn, kq_index_t qos_index);
static void knote_adjust_qos(struct kqueue *kq, struct knote *kn, int result);
static void knote_reset_priority(struct knote *kn, pthread_priority_t pp);
static kq_index_t knote_get_qos_override_index(struct knote *kn);
static void knote_set_qos_overcommit(struct knote *kn);

static zone_t knote_zone;
static zone_t kqfile_zone;
static zone_t kqworkq_zone;
static zone_t kqworkloop_zone;
#if DEVELOPMENT || DEBUG
#define KEVENT_PANIC_ON_WORKLOOP_OWNERSHIP_LEAK  (1U << 0)
#define KEVENT_PANIC_ON_NON_ENQUEUED_PROCESS     (1U << 1)
#define KEVENT_PANIC_BOOT_ARG_INITIALIZED        (1U << 31)

#define KEVENT_PANIC_DEFAULT_VALUE (0)
static uint32_t
kevent_debug_flags(void)
{
        static uint32_t flags = KEVENT_PANIC_DEFAULT_VALUE;

        if ((flags & KEVENT_PANIC_BOOT_ARG_INITIALIZED) == 0) {
                uint32_t value = 0;
                if (!PE_parse_boot_argn("kevent_debug", &value, sizeof(value))) {
                        value = KEVENT_PANIC_DEFAULT_VALUE;
                }
                value |= KEVENT_PANIC_BOOT_ARG_INITIALIZED;
                os_atomic_store(&flags, value, relaxed);
        }
        return flags;
}
#endif

#define KN_HASH(val, mask)      (((val) ^ (val >> 8)) & (mask))

/* placeholder for not-yet-implemented filters */
static int filt_badattach(struct knote *kn, struct kevent_internal_s *kev);
static int filt_badevent(struct knote *kn, long hint);
SECURITY_READ_ONLY_EARLY(static struct filterops) bad_filtops = {
        .f_attach = filt_badattach,
};

#if CONFIG_MEMORYSTATUS
extern const struct filterops memorystatus_filtops;
#endif /* CONFIG_MEMORYSTATUS */
extern const struct filterops fs_filtops;
extern const struct filterops sig_filtops;
extern const struct filterops machport_filtops;
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 file_filtops;
const static struct filterops kqread_filtops;
const static struct filterops proc_filtops;
const static struct filterops timer_filtops;
const static struct filterops user_filtops;
const static struct filterops workloop_filtops;

/*
 *
 * 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.
 */
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,
        [~EVFILT_VM]                    = &bad_filtops,
        [~EVFILT_SOCK]                  = &file_filtops,
#if CONFIG_MEMORYSTATUS
        [~EVFILT_MEMORYSTATUS]          = &memorystatus_filtops,
#else
        [~EVFILT_MEMORYSTATUS]          = &bad_filtops,
#endif
        [~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);

static inline struct kqworkloop *
kqr_kqworkloop(struct kqrequest *kqr)
{
        if (kqr->kqr_state & KQR_WORKLOOP) {
                return __container_of(kqr, struct kqworkloop, kqwl_request);
        }
        return NULL;
}

static inline kqueue_t
kqr_kqueue(proc_t p, struct kqrequest *kqr)
{
        kqueue_t kqu;
        if (kqr->kqr_state & KQR_WORKLOOP) {
                kqu.kqwl = kqr_kqworkloop(kqr);
        } else {
                kqu.kqwq = (struct kqworkq *)p->p_fd->fd_wqkqueue;
                assert(kqr >= kqu.kqwq->kqwq_request &&
                                kqr < kqu.kqwq->kqwq_request + KQWQ_NBUCKETS);
        }
        return kqu;
}

static inline boolean_t
is_workqueue_thread(thread_t thread)
{
        return (thread_get_tag(thread) & THREAD_TAG_WORKQUEUE);
}

/*
 * kqueue/note lock implementations
 *
 *      The kqueue lock guards the kq state, the state of its queues,
 *      and the kqueue-aware status and locks 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).
 *
 *      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.
 */
static lck_grp_attr_t *kq_lck_grp_attr;
static lck_grp_t *kq_lck_grp;
static lck_attr_t *kq_lck_attr;

static inline void
kqlock(kqueue_t kqu)
{
        lck_spin_lock(&kqu.kq->kq_lock);
}

static inline void
kqlock_held(__assert_only kqueue_t kqu)
{
        LCK_SPIN_ASSERT(&kqu.kq->kq_lock, LCK_ASSERT_OWNED);
}

static inline void
kqunlock(kqueue_t kqu)
{
        lck_spin_unlock(&kqu.kq->kq_lock);
}

static inline void
kq_req_lock(kqueue_t kqu)
{
        assert(kqu.kq->kq_state & (KQ_WORKLOOP | KQ_WORKQ));
        lck_spin_lock(&kqu.kq->kq_reqlock);
}

static inline void
kq_req_unlock(kqueue_t kqu)
{
        assert(kqu.kq->kq_state & (KQ_WORKLOOP | KQ_WORKQ));
        lck_spin_unlock(&kqu.kq->kq_reqlock);
}

static inline void
kq_req_held(__assert_only kqueue_t kqu)
{
        assert(kqu.kq->kq_state & (KQ_WORKLOOP | KQ_WORKQ));
        LCK_SPIN_ASSERT(&kqu.kq->kq_reqlock, LCK_ASSERT_OWNED);
}

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);
}

#pragma mark knote locks

/*
 * Enum used by the knote_lock_* functions.
 *
 * KNOTE_KQ_LOCK_ALWAYS
 *   The function will always return with the kq lock held.
 *
 * KNOTE_KQ_UNLOCK_ON_SUCCESS
 *   The function will return with the kq lock held if it was successful
 *   (knote_lock() is the only function that can fail).
 *
 * KNOTE_KQ_UNLOCK_ON_FAILURE
 *   The function will return with the kq lock held if it was unsuccessful
 *   (knote_lock() is the only function that can fail).
 *
 * KNOTE_KQ_UNLOCK:
 *   The function returns with the kq unlocked.
 */
#define KNOTE_KQ_LOCK_ALWAYS      0x0
#define KNOTE_KQ_LOCK_ON_SUCCESS  0x1
#define KNOTE_KQ_LOCK_ON_FAILURE  0x2
#define KNOTE_KQ_UNLOCK           0x3

#if DEBUG || DEVELOPMENT
__attribute__((noinline, not_tail_called, disable_tail_calls))
void knote_lock_ctx_chk(struct knote_lock_ctx *knlc)
{
        /* evil hackery to make sure no one forgets to unlock */
        assert(knlc->knlc_state == KNOTE_LOCK_CTX_UNLOCKED);
}
#endif

static struct knote_lock_ctx *
knote_lock_ctx_find(struct kqueue *kq, struct knote *kn)
{
        struct knote_lock_ctx *ctx;
        LIST_FOREACH(ctx, &kq->kq_knlocks, knlc_le) {
                if (ctx->knlc_knote == kn) return ctx;
        }
        panic("knote lock context not found: %p", kn);
        __builtin_trap();
}

/* slowpath of knote_lock() */
__attribute__((noinline))
static bool __result_use_check
knote_lock_slow(struct kqueue *kq, struct knote *kn,
                struct knote_lock_ctx *knlc, int kqlocking)
{
        kqlock_held(kq);

        struct knote_lock_ctx *owner_lc = knote_lock_ctx_find(kq, kn);
        thread_t owner_thread = owner_lc->knlc_thread;

#if DEBUG || DEVELOPMENT
        knlc->knlc_state = KNOTE_LOCK_CTX_WAITING;
#endif

        thread_reference(owner_thread);
        TAILQ_INSERT_TAIL(&owner_lc->knlc_head, knlc, knlc_tqe);
        assert_wait(&kn->kn_status, THREAD_UNINT | THREAD_WAIT_NOREPORT);
        kqunlock(kq);

        if (thread_handoff_deallocate(owner_thread) == THREAD_RESTART) {
                if (kqlocking == KNOTE_KQ_LOCK_ALWAYS ||
                                kqlocking == KNOTE_KQ_LOCK_ON_FAILURE) {
                        kqlock(kq);
                }
#if DEBUG || DEVELOPMENT
                assert(knlc->knlc_state == KNOTE_LOCK_CTX_WAITING);
                knlc->knlc_state = KNOTE_LOCK_CTX_UNLOCKED;
#endif
                return false;
        }
#if DEBUG || DEVELOPMENT
                assert(knlc->knlc_state == KNOTE_LOCK_CTX_LOCKED);
#endif
        if (kqlocking == KNOTE_KQ_LOCK_ALWAYS ||
                        kqlocking == KNOTE_KQ_LOCK_ON_SUCCESS) {
                kqlock(kq);
        }
        return true;
}

/*
 * Attempts to take the "knote" lock.
 *
 * Called with the kqueue lock held.
 *
 * Returns true if the knote lock is acquired, false if it has been dropped
 */
static bool __result_use_check
knote_lock(struct kqueue *kq, struct knote *kn, struct knote_lock_ctx *knlc,
                int kqlocking)
{
        kqlock_held(kq);

#if DEBUG || DEVELOPMENT
        assert(knlc->knlc_state == KNOTE_LOCK_CTX_UNLOCKED);
#endif
        knlc->knlc_knote = kn;
        knlc->knlc_thread = current_thread();
        TAILQ_INIT(&knlc->knlc_head);

        if (__improbable(kn->kn_status & KN_LOCKED)) {
                return knote_lock_slow(kq, kn, knlc, kqlocking);
        }

        /*
         * When the knote will be dropped, the knote lock is taken before
         * KN_DROPPING is set, and then the knote will be removed from any
         * hash table that references it before the lock is canceled.
         */
        assert((kn->kn_status & KN_DROPPING) == 0);
        LIST_INSERT_HEAD(&kq->kq_knlocks, knlc, knlc_le);
        kn->kn_status |= KN_LOCKED;
#if DEBUG || DEVELOPMENT
        knlc->knlc_state = KNOTE_LOCK_CTX_LOCKED;
#endif

        if (kqlocking == KNOTE_KQ_UNLOCK ||
                        kqlocking == KNOTE_KQ_LOCK_ON_FAILURE) {
                kqunlock(kq);
        }
        return true;
}

/*
 * Unlocks a knote successfully locked with knote_lock().
 *
 * Called with the kqueue lock held.
 *
 * Returns with the kqueue lock held according to KNOTE_KQ_* flags
 */
static void
knote_unlock(struct kqueue *kq, struct knote *kn,
                struct knote_lock_ctx *knlc, int flags)
{
        kqlock_held(kq);

        assert(knlc->knlc_knote == kn);
        assert(kn->kn_status & KN_LOCKED);
#if DEBUG || DEVELOPMENT
        assert(knlc->knlc_state == KNOTE_LOCK_CTX_LOCKED);
#endif

        struct knote_lock_ctx *next_owner_lc = TAILQ_FIRST(&knlc->knlc_head);

        LIST_REMOVE(knlc, knlc_le);

        if (next_owner_lc) {
                assert(next_owner_lc->knlc_knote == kn);
                TAILQ_REMOVE(&knlc->knlc_head, next_owner_lc, knlc_tqe);

                assert(TAILQ_EMPTY(&next_owner_lc->knlc_head));
                TAILQ_CONCAT(&next_owner_lc->knlc_head, &knlc->knlc_head, knlc_tqe);
                LIST_INSERT_HEAD(&kq->kq_knlocks, next_owner_lc, knlc_le);
#if DEBUG || DEVELOPMENT
                next_owner_lc->knlc_state = KNOTE_LOCK_CTX_LOCKED;
#endif
        } else {
                kn->kn_status &= ~KN_LOCKED;
        }
        if (kn->kn_inuse == 0) {
                /*
                 * No f_event() in flight anymore, we can leave QoS "Merge" mode
                 *
                 * See knote_should_apply_qos_override()
                 */
                kn->kn_status &= ~KN_MERGE_QOS;
        }
        if (flags & KNOTE_KQ_UNLOCK) {
                kqunlock(kq);
        }
        if (next_owner_lc) {
                thread_wakeup_thread(&kn->kn_status, next_owner_lc->knlc_thread);
        }
#if DEBUG || DEVELOPMENT
        knlc->knlc_state = KNOTE_LOCK_CTX_UNLOCKED;
#endif
}

/*
 * Aborts all waiters for a knote lock, and unlock the knote.
 *
 * Called with the kqueue lock held.
 *
 * Returns with the kqueue lock held according to KNOTE_KQ_* flags
 */
static void
knote_unlock_cancel(struct kqueue *kq, struct knote *kn,
                struct knote_lock_ctx *knlc, int kqlocking)
{
        kqlock_held(kq);

        assert(knlc->knlc_knote == kn);
        assert(kn->kn_status & KN_LOCKED);
        assert(kn->kn_status & KN_DROPPING);

        LIST_REMOVE(knlc, knlc_le);
        kn->kn_status &= ~KN_LOCKED;

        if (kqlocking == KNOTE_KQ_UNLOCK ||
                        kqlocking == KNOTE_KQ_LOCK_ON_FAILURE) {
                kqunlock(kq);
        }
        if (!TAILQ_EMPTY(&knlc->knlc_head)) {
                thread_wakeup_with_result(&kn->kn_status, THREAD_RESTART);
        }
#if DEBUG || DEVELOPMENT
        knlc->knlc_state = KNOTE_LOCK_CTX_UNLOCKED;
#endif
}

/*
 * Call the f_event hook of a given filter.
 *
 * Takes a use count to protect against concurrent drops.
 */
static void
knote_call_filter_event(struct kqueue *kq, struct knote *kn, long hint)
{
        int result, dropping = 0;

        kqlock_held(kq);

        if (kn->kn_status & (KN_DROPPING | KN_VANISHED))
                return;

        kn->kn_inuse++;
        kqunlock(kq);
        result = filter_call(knote_fops(kn), f_event(kn, hint));
        kqlock(kq);

        dropping = (kn->kn_status & KN_DROPPING);

        if (!dropping && (result & FILTER_ACTIVE)) {
                if (result & FILTER_ADJUST_EVENT_QOS_BIT)
                        knote_adjust_qos(kq, kn, result);
                knote_activate(kn);
        }

        if (--kn->kn_inuse == 0) {
                if ((kn->kn_status & KN_LOCKED) == 0) {
                        /*
                         * We're the last f_event() call and there's no other f_* call in
                         * flight, we can leave QoS "Merge" mode.
                         *
                         * See knote_should_apply_qos_override()
                         */
                        kn->kn_status &= ~KN_MERGE_QOS;
                }
                if (dropping) {
                        waitq_wakeup64_all((struct waitq *)&kq->kq_wqs,
                                        CAST_EVENT64_T(&kn->kn_inuse),
                                        THREAD_AWAKENED, WAITQ_ALL_PRIORITIES);
                }
        }
}

/*
 * Called by knote_drop() to wait for the last f_event() caller to be done.
 *
 *      - kq locked at entry
 *      - kq unlocked at exit
 */
static void
knote_wait_for_filter_events(struct kqueue *kq, struct knote *kn)
{
        wait_result_t wr = THREAD_NOT_WAITING;

        kqlock_held(kq);

        assert(kn->kn_status & KN_DROPPING);

        if (kn->kn_inuse) {
                wr = waitq_assert_wait64((struct waitq *)&kq->kq_wqs,
                                CAST_EVENT64_T(&kn->kn_inuse),
                                THREAD_UNINT | THREAD_WAIT_NOREPORT, TIMEOUT_WAIT_FOREVER);
        }
        kqunlock(kq);
        if (wr == THREAD_WAITING) {
                thread_block(THREAD_CONTINUE_NULL);
        }
}

#pragma mark file_filtops

static int
filt_fileattach(struct knote *kn, struct kevent_internal_s *kev)
{
        return fo_kqfilter(kn->kn_fp, kn, kev, vfs_context_current());
}

SECURITY_READ_ONLY_EARLY(static struct filterops) file_filtops = {
        .f_isfd = 1,
        .f_attach = filt_fileattach,
};

#pragma mark kqread_filtops

#define f_flag f_fglob->fg_flag
#define f_ops f_fglob->fg_ops
#define f_data f_fglob->fg_data

static void
filt_kqdetach(struct knote *kn)
{
        struct kqfile *kqf = (struct kqfile *)kn->kn_fp->f_data;
        struct kqueue *kq = &kqf->kqf_kqueue;

        kqlock(kq);
        KNOTE_DETACH(&kqf->kqf_sel.si_note, kn);
        kqunlock(kq);
}

static int
filt_kqueue(struct knote *kn, __unused long hint)
{
        struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;

        return (kq->kq_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;
        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;
        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;
}

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,
};

#pragma mark proc_filtops

static int
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) {
                knote_set_error(kn, ENOTSUP);
                return 0;
        }

        p = proc_find(kn->kn_id);
        if (p == NULL) {
                knote_set_error(kn, ESRCH);
                return 0;
        }

        const int NoteExitStatusBits = NOTE_EXIT | NOTE_EXITSTATUS;

        if ((kn->kn_sfflags & NoteExitStatusBits) == NoteExitStatusBits)
                do {
                        pid_t selfpid = proc_selfpid();

                        if (p->p_ppid == selfpid)
                                break;  /* parent => ok */

                        if ((p->p_lflag & P_LTRACED) != 0 &&
                            (p->p_oppid == selfpid))
                                break;  /* parent-in-waiting => ok */

                        proc_rele(p);
                        knote_set_error(kn, EACCES);
                        return 0;
                } while (0);

        proc_klist_lock();

        kn->kn_ptr.p_proc = p;          /* store the proc handle */

        KNOTE_ATTACH(&p->p_klist, kn);

        proc_klist_unlock();

        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,
 * the pointer to the process will have already been nulled out.
 */
static void
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;
                KNOTE_DETACH(&p->p_klist, kn);
        }

        proc_klist_unlock();
}

static int
filt_proc(struct knote *kn, long hint)
{
        u_int event;

        /* ALWAYS CALLED WITH proc_klist_lock */

        /*
         * 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;

        /*
         * 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 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);
                }
                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;
                        }
                }
        }

        /* if we have any matching state, activate the knote */
        return (kn->kn_fflags != 0);
}

static int
filt_proctouch(struct knote *kn, struct kevent_internal_s *kev)
{
        int res;

        proc_klist_lock();

        /* accept new filter flags and mask off output events no long interesting */
        kn->kn_sfflags = kev->fflags;

        /* 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_procprocess(struct knote *kn, struct filt_process_s *data, struct kevent_internal_s *kev)
{
#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;
        }
        proc_klist_unlock();
        return res;
}

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,
};

#pragma mark timer_filtops

struct filt_timer_params {
        uint64_t deadline; /* deadline in abs/cont time
                                                  (or 0 if NOTE_ABSOLUTE and deadline is in past) */
        uint64_t leeway;   /* leeway in abstime, or 0 if none */
        uint64_t interval; /* interval in abstime or 0 if non-repeating 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_hookid        timer state
 *
 * TIMER_IDLE:
 *   The timer has either never been scheduled or been cancelled.
 *   It is safe to schedule a new one in this state.
 *
 * TIMER_ARMED:
 *   The timer has been scheduled
 *
 * TIMER_FIRED
 *   The timer has fired and an event needs to be delivered.
 *   When in this state, the callout may still be running.
 *
 * TIMER_IMMEDIATE
 *   The timer has fired at registration time, and the callout was never
 *   dispatched.
 */
#define TIMER_IDLE       0x0
#define TIMER_ARMED      0x1
#define TIMER_FIRED      0x2
#define TIMER_IMMEDIATE  0x3

static void
filt_timer_set_params(struct knote *kn, struct filt_timer_params *params)
{
        kn->kn_ext[0] = params->deadline;
        kn->kn_ext[1] = params->leeway;
        kn->kn_sdata  = params->interval;
}

/*
 * filt_timervalidate - process data from user
 *
 * 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
 *
 * Output:
 *      struct filter_timer_params to apply to the filter with
 *      filt_timer_set_params when changes are ready to be commited.
 *
 * Returns:
 *      EINVAL          Invalid user data parameters
 *      ERANGE          Various overflows with the parameters
 *
 * Called with timer filter lock held.
 */
static int
filt_timervalidate(const struct kevent_internal_s *kev,
                struct filt_timer_params *params)
{
        /*
         * There are 5 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.
         */

        uint64_t multiplier;

        boolean_t use_abstime = FALSE;

        switch (kev->fflags & (NOTE_SECONDS|NOTE_USECONDS|NOTE_NSECONDS|NOTE_MACHTIME)) {
        case NOTE_SECONDS:
                multiplier = NSEC_PER_SEC;
                break;
        case NOTE_USECONDS:
                multiplier = NSEC_PER_USEC;
                break;
        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);
        }

        /* transform the leeway in kn_ext[1] to same time scale */
        if (kev->fflags & NOTE_LEEWAY) {
                uint64_t leeway_abs;

                if (use_abstime) {
                        leeway_abs = (uint64_t)kev->ext[1];
                } else  {
                        uint64_t leeway_ns;
                        if (os_mul_overflow((uint64_t)kev->ext[1], multiplier, &leeway_ns))
                                return (ERANGE);

                        nanoseconds_to_absolutetime(leeway_ns, &leeway_abs);
                }

                params->leeway = leeway_abs;
        } else {
                params->leeway = 0;
        }

        if (kev->fflags & NOTE_ABSOLUTE) {
                uint64_t deadline_abs;

                if (use_abstime) {
                        deadline_abs = (uint64_t)kev->data;
                } else {
                        uint64_t calendar_deadline_ns;

                        if (os_mul_overflow((uint64_t)kev->data, multiplier, &calendar_deadline_ns))
                                return (ERANGE);

                        /* calendar_deadline_ns is in nanoseconds since the epoch */

                        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 (kev->fflags & 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 */
                        }
                }

                params->deadline = deadline_abs;
                params->interval = 0; /* NOTE_ABSOLUTE is non-repeating */
        } else if (kev->data < 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.
                 *
                 * 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.
                 */

                params->deadline = 0; /* expire immediately */
                params->interval = 0; /* non-repeating */
        } else {
                uint64_t interval_abs = 0;

                if (use_abstime) {
                        interval_abs = (uint64_t)kev->data;
                } else {
                        uint64_t interval_ns;
                        if (os_mul_overflow((uint64_t)kev->data, multiplier, &interval_ns))
                                return (ERANGE);

                        nanoseconds_to_absolutetime(interval_ns, &interval_abs);
                }

                uint64_t deadline = 0;

                if (kev->fflags & NOTE_MACH_CONTINUOUS_TIME)
                        clock_continuoustime_interval_to_deadline(interval_abs, &deadline);
                else
                        clock_absolutetime_interval_to_deadline(interval_abs, &deadline);

                params->deadline = deadline;
                params->interval = interval_abs;
        }

        return (0);
}

/*
 * filt_timerexpire - the timer callout routine
 */
static void
filt_timerexpire(void *knx, __unused void *spare)
{
        struct knote *kn = knx;
        int v;

        if (os_atomic_cmpxchgv(&kn->kn_hookid, TIMER_ARMED, TIMER_FIRED,
                        &v, relaxed)) {
                // our f_event always would say FILTER_ACTIVE,
                // so be leaner and just do it.
                struct kqueue *kq = knote_get_kq(kn);
                kqlock(kq);
                knote_activate(kn);
                kqunlock(kq);
        } else {
                /*
                 * From TIMER_ARMED, the only allowed transition are:
                 * - to TIMER_FIRED through the timer callout just above
                 * - to TIMER_IDLE due to filt_timercancel() which will wait for the
                 *   timer callout (and any possible invocation of filt_timerexpire) to
                 *   have finished before the state is changed again.
                 */
                assert(v == TIMER_IDLE);
        }
}

static void
filt_timercancel(struct knote *kn)
{
        if (os_atomic_xchg(&kn->kn_hookid, TIMER_IDLE, relaxed) == TIMER_ARMED) {
                /* cancel the thread call and wait for any filt_timerexpire in flight */
                thread_call_cancel_wait((thread_call_t)kn->kn_hook);
        }
}

/*
 * Does this deadline needs a timer armed for it, or has it expired?
 */
static bool
filt_timer_is_ready(struct knote *kn)
{
        uint64_t now, deadline = kn->kn_ext[0];

        if (deadline == 0) {
                return true;
        }

        if (kn->kn_sfflags & NOTE_MACH_CONTINUOUS_TIME) {
                now = mach_continuous_time();
        } else {
                now = mach_absolute_time();
        }
        return deadline <= now;
}

/*
 * Arm a timer
 *
 * It is the responsibility of the caller to make sure the timer call
 * has completed or been cancelled properly prior to arming it.
 */
static void
filt_timerarm(struct knote *kn)
{
        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;

        assert(os_atomic_load(&kn->kn_hookid, relaxed) == TIMER_IDLE);

        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;

        os_atomic_store(&kn->kn_hookid, TIMER_ARMED, relaxed);
        thread_call_enter_delayed_with_leeway((thread_call_t)kn->kn_hook, NULL,
                        deadline, leeway, timer_flags);
}

/*
 * Allocate a thread call for the knote's lifetime, and kick off the timer.
 */
static int
filt_timerattach(struct knote *kn, struct kevent_internal_s *kev)
{
        thread_call_t callout;
        struct filt_timer_params params;
        int error;

        if ((error = filt_timervalidate(kev, &params)) != 0) {
                knote_set_error(kn, error);
                return 0;
        }

        callout = thread_call_allocate_with_options(filt_timerexpire,
                        (thread_call_param_t)kn, THREAD_CALL_PRIORITY_HIGH,
                        THREAD_CALL_OPTIONS_ONCE);

        if (NULL == callout) {
                knote_set_error(kn, ENOMEM);
                return 0;
        }

        filt_timer_set_params(kn, &params);
        kn->kn_hook = callout;
        kn->kn_flags |= EV_CLEAR;
        os_atomic_store(&kn->kn_hookid, TIMER_IDLE, relaxed);

        /* NOTE_ABSOLUTE implies EV_ONESHOT */
        if (kn->kn_sfflags & NOTE_ABSOLUTE)
                kn->kn_flags |= EV_ONESHOT;

        if (filt_timer_is_ready(kn)) {
                os_atomic_store(&kn->kn_hookid, TIMER_IMMEDIATE, relaxed);
                return FILTER_ACTIVE;
        } else {
                filt_timerarm(kn);
                return 0;
        }
}

/*
 * Shut down the timer if it's running, and free the callout.
 */
static void
filt_timerdetach(struct knote *kn)
{
        __assert_only boolean_t freed;

        /*
         * Unconditionally cancel to make sure there can't be any filt_timerexpire()
         * running anymore.
         */
        thread_call_cancel_wait((thread_call_t)kn->kn_hook);
        freed = thread_call_free((thread_call_t)kn->kn_hook);
        assert(freed);
}

/*
 * 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_timertouch(struct knote *kn, struct kevent_internal_s *kev)
{
        struct filt_timer_params params;
        uint32_t changed_flags = (kn->kn_sfflags ^ kev->fflags);
        int error;

        if (changed_flags & NOTE_ABSOLUTE) {
                kev->flags |= EV_ERROR;
                kev->data = EINVAL;
                return 0;
        }

        if ((error = filt_timervalidate(kev, &params)) != 0) {
                kev->flags |= EV_ERROR;
                kev->data = error;
                return 0;
        }

        /* capture the new values used to compute deadline */
        filt_timercancel(kn);
        filt_timer_set_params(kn, &params);
        kn->kn_sfflags = kev->fflags;

        if (filt_timer_is_ready(kn)) {
                os_atomic_store(&kn->kn_hookid, TIMER_IMMEDIATE, relaxed);
                return FILTER_ACTIVE | FILTER_UPDATE_REQ_QOS;
        } else {
                filt_timerarm(kn);
                return FILTER_UPDATE_REQ_QOS;
        }
}

/*
 * filt_timerprocess - query state of knote and snapshot event 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 int
filt_timerprocess(
        struct knote *kn,
        __unused struct filt_process_s *data,
        struct kevent_internal_s *kev)
{
        /*
         * filt_timerprocess is serialized with any filter routine except for
         * filt_timerexpire which atomically does a TIMER_ARMED -> TIMER_FIRED
         * transition, and on success, activates the knote.
         *
         * Hence, we don't need atomic modifications of the state, only to peek at
         * whether we see any of the "FIRED" state, and if we do, it is safe to
         * do simple state machine transitions.
         */
        switch (os_atomic_load(&kn->kn_hookid, relaxed)) {
        case TIMER_IDLE:
        case TIMER_ARMED:
                /*
                 * This can happen if a touch resets a timer that had fired
                 * without being processed
                 */
                return 0;
        }

        os_atomic_store(&kn->kn_hookid, TIMER_IDLE, relaxed);

        /*
         * 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? */

        if (kn->kn_sdata == 0) {
                kev->data = 1;
        } else {
                /*
                 * 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...
                 */

                uint64_t now;

                if (kn->kn_sfflags & NOTE_MACH_CONTINUOUS_TIME)
                        now = mach_continuous_time();
                else
                        now = mach_absolute_time();

                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.
                 */
                assert(num_fired > 0);

                /* report how many intervals have elapsed to the user */
                kev->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;

                        /*
                         * This can't shortcut setting up the thread call, because
                         * knote_process deactivates EV_CLEAR knotes unconditionnally.
                         */
                        filt_timerarm(kn);
                }
        }

        return FILTER_ACTIVE;
}

SECURITY_READ_ONLY_EARLY(static struct filterops) timer_filtops = {
        .f_extended_codes = true,
        .f_attach   = filt_timerattach,
        .f_detach   = filt_timerdetach,
        .f_event    = filt_badevent,
        .f_touch    = filt_timertouch,
        .f_process  = filt_timerprocess,
};

#pragma mark user_filtops

static int
filt_userattach(struct knote *kn, __unused struct kevent_internal_s *kev)
{
        if (kn->kn_sfflags & NOTE_TRIGGER) {
                kn->kn_hookid = FILTER_ACTIVE;
        } else {
                kn->kn_hookid = 0;
        }
        return (kn->kn_hookid);
}

static void
filt_userdetach(__unused struct knote *kn)
{
        /* EVFILT_USER knotes are not attached to anything in the kernel */
}

static int
filt_usertouch(struct knote *kn, struct kevent_internal_s *kev)
{
        uint32_t ffctrl;
        int fflags;

        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 (kev->fflags & NOTE_TRIGGER) {
                kn->kn_hookid = FILTER_ACTIVE;
        }
        return (int)kn->kn_hookid;
}

static int
filt_userprocess(
        struct knote *kn,
        __unused struct filt_process_s *data,
        struct kevent_internal_s *kev)
{
        int result = (int)kn->kn_hookid;

        if (result) {
                *kev = kn->kn_kevent;
                kev->fflags = 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;
                }
        }

        return result;
}

SECURITY_READ_ONLY_EARLY(static struct filterops) user_filtops = {
        .f_extended_codes = true,
        .f_attach  = filt_userattach,
        .f_detach  = filt_userdetach,
        .f_event   = filt_badevent,
        .f_touch   = filt_usertouch,
        .f_process = filt_userprocess,
};

#pragma mark workloop_filtops

static inline void
filt_wllock(struct kqworkloop *kqwl)
{
        lck_mtx_lock(&kqwl->kqwl_statelock);
}

static inline void
filt_wlunlock(struct kqworkloop *kqwl)
{
        lck_mtx_unlock(&kqwl->kqwl_statelock);
}

/*
 * Returns true when the interlock for the turnstile is the workqueue lock
 *
 * When this is the case, all turnstiles operations are delegated
 * to the workqueue subsystem.
 *
 * This is required because kqueue_threadreq_bind_prepost only holds the
 * workqueue lock but needs to move the inheritor from the workloop turnstile
 * away from the creator thread, so that this now fulfilled request cannot be
 * picked anymore by other threads.
 */
static inline bool
filt_wlturnstile_interlock_is_workq(struct kqworkloop *kqwl)
{
        struct kqrequest *kqr = &kqwl->kqwl_request;
        return (kqr->kqr_state & KQR_THREQUESTED) &&
                        (kqr->kqr_thread == THREAD_NULL);
}

static void
filt_wlupdate_inheritor(struct kqworkloop *kqwl, struct turnstile *ts,
                turnstile_update_flags_t flags)
{
        turnstile_inheritor_t inheritor = TURNSTILE_INHERITOR_NULL;
        struct kqrequest *kqr = &kqwl->kqwl_request;

        /*
         * binding to the workq should always happen through
         * workq_kern_threadreq_update_inheritor()
         */
        assert(!filt_wlturnstile_interlock_is_workq(kqwl));

        if ((inheritor = kqwl->kqwl_owner)) {
                flags |= TURNSTILE_INHERITOR_THREAD;
        } else if ((inheritor = kqr->kqr_thread)) {
                flags |= TURNSTILE_INHERITOR_THREAD;
        }

        turnstile_update_inheritor(ts, inheritor, flags);
}

#define FILT_WLATTACH 0
#define FILT_WLTOUCH  1
#define FILT_WLDROP   2

__result_use_check
static int
filt_wlupdate(struct kqworkloop *kqwl, struct knote *kn,
                struct kevent_internal_s *kev, kq_index_t qos_index, int op)
{
        user_addr_t uaddr = CAST_USER_ADDR_T(kev->ext[EV_EXTIDX_WL_ADDR]);
        struct kqrequest *kqr = &kqwl->kqwl_request;
        thread_t cur_owner, new_owner, extra_thread_ref = THREAD_NULL;
        kq_index_t cur_owner_override = THREAD_QOS_UNSPECIFIED;
        int action = KQWL_UTQ_NONE, error = 0;
        bool needs_wake = false, needs_wllock = false;
        uint64_t kdata = kev->ext[EV_EXTIDX_WL_VALUE];
        uint64_t mask = kev->ext[EV_EXTIDX_WL_MASK];
        uint64_t udata = 0;

        if (kev->fflags & (NOTE_WL_END_OWNERSHIP | NOTE_WL_DISCOVER_OWNER)) {
                /*
                 * If we're maybe going to change the kqwl_owner,
                 * then we need to hold the filt_wllock().
                 */
                needs_wllock = true;
        } else if (kqr->kqr_thread == current_thread()) {
                /*
                 * <rdar://problem/41531764> Servicer updates need to be serialized with
                 * any ownership change too, as the kqr_thread value influences the
                 * outcome of handling NOTE_WL_DISCOVER_OWNER.
                 */
                needs_wllock = true;
        }

        if (needs_wllock) {
                filt_wllock(kqwl);
                /*
                 * The kqwl owner is set under both the req and filter lock,
                 * meaning it's fine to look at it under any.
                 */
                new_owner = cur_owner = kqwl->kqwl_owner;
        } else {
                new_owner = cur_owner = THREAD_NULL;
        }

        /*
         * Phase 1:
         *
         * If asked, load the uint64 value at the user provided address and compare
         * it against the passed in mask and expected value.
         *
         * If NOTE_WL_DISCOVER_OWNER is specified, translate the loaded name as
         * a thread reference.
         *
         * If NOTE_WL_END_OWNERSHIP is specified and the currently known owner is
         * the current thread, then end ownership.
         *
         * Lastly decide whether we need to perform a QoS update.
         */
        if (uaddr) {
                error = copyin_word(uaddr, &udata, sizeof(udata));
                if (error) {
                        goto out;
                }

                /* Update state as copied in.  */
                kev->ext[EV_EXTIDX_WL_VALUE] = udata;

                if ((udata & mask) != (kdata & mask)) {
                        error = ESTALE;
                } else if (kev->fflags & NOTE_WL_DISCOVER_OWNER) {
                        /*
                         * Decipher the owner port name, and translate accordingly.
                         * The low 2 bits were borrowed for other flags, so mask them off.
                         *
                         * Then attempt translation to a thread reference or fail.
                         */
                        mach_port_name_t name = (mach_port_name_t)udata & ~0x3;
                        if (name != MACH_PORT_NULL) {
                                name = ipc_entry_name_mask(name);
                                extra_thread_ref = port_name_to_thread(name);
                                if (extra_thread_ref == THREAD_NULL) {
                                        error = EOWNERDEAD;
                                        goto out;
                                }
                                new_owner = extra_thread_ref;
                        }
                }
        }

        if ((kev->fflags & NOTE_WL_END_OWNERSHIP) && new_owner == current_thread()) {
                new_owner = THREAD_NULL;
        }

        if (error == 0) {
                if ((kev->fflags & NOTE_WL_THREAD_REQUEST) && (kev->flags & EV_DELETE)) {
                        action = KQWL_UTQ_SET_QOS_INDEX;
                } else if (qos_index && kqr->kqr_qos_index != qos_index) {
                        action = KQWL_UTQ_SET_QOS_INDEX;
                }

                if (op == FILT_WLTOUCH) {
                        /*
                         * 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;
                        if (kev->fflags & NOTE_WL_SYNC_WAKE) {
                                needs_wake = (kn->kn_hook != THREAD_NULL);
                        }
                } else if (op == FILT_WLDROP) {
                        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;
                                needs_wake = (kn->kn_hook != THREAD_NULL);
                        }
                }
        }

        /*
         * Phase 2:
         *
         * Commit ownership and QoS changes if any, possibly wake up waiters
         */

        if (cur_owner == new_owner && action == KQWL_UTQ_NONE && !needs_wake) {
                goto out;
        }

        kq_req_lock(kqwl);

        /* If already tracked as servicer, don't track as owner */
        if (new_owner == kqr->kqr_thread) {
                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_owner_override = kqworkloop_owner_override(kqwl);

                if (cur_owner) {
                        thread_ends_owning_workloop(cur_owner);
                }

                if (new_owner) {
                        /* override it before we drop the old */
                        if (cur_owner_override != THREAD_QOS_UNSPECIFIED) {
                                thread_add_ipc_override(new_owner, cur_owner_override);
                        }
                        thread_starts_owning_workloop(new_owner);
                        if ((kqr->kqr_state & KQR_THREQUESTED) && !kqr->kqr_thread) {
                                if (action == KQWL_UTQ_NONE) {
                                        action = KQWL_UTQ_REDRIVE_EVENTS;
                                }
                        }
                } else {
                        if ((kqr->kqr_state & (KQR_THREQUESTED | KQR_WAKEUP)) == KQR_WAKEUP) {
                                if (action == KQWL_UTQ_NONE) {
                                        action = KQWL_UTQ_REDRIVE_EVENTS;
                                }
                        }
                }
        }

        struct turnstile *ts = kqwl->kqwl_turnstile;
        bool wl_inheritor_updated = false;

        if (action != KQWL_UTQ_NONE) {
                kqworkloop_update_threads_qos(kqwl, action, qos_index);
        }

        if (cur_owner != new_owner && ts) {
                if (action == KQWL_UTQ_REDRIVE_EVENTS) {
                        /*
                         * Note that when action is KQWL_UTQ_REDRIVE_EVENTS,
                         * the code went through workq_kern_threadreq_initiate()
                         * and the workqueue has set the inheritor already
                         */
                        assert(filt_wlturnstile_interlock_is_workq(kqwl));
                } else if (filt_wlturnstile_interlock_is_workq(kqwl)) {
                        workq_kern_threadreq_lock(kqwl->kqwl_p);
                        workq_kern_threadreq_update_inheritor(kqwl->kqwl_p, kqr, new_owner,
                                        ts, TURNSTILE_IMMEDIATE_UPDATE);
                        workq_kern_threadreq_unlock(kqwl->kqwl_p);
                        if (!filt_wlturnstile_interlock_is_workq(kqwl)) {
                                /*
                                 * If the workq is no longer the interlock, then
                                 * workq_kern_threadreq_update_inheritor() has finished a bind
                                 * and we need to fallback to the regular path.
                                 */
                                filt_wlupdate_inheritor(kqwl, ts, TURNSTILE_IMMEDIATE_UPDATE);
                        }
                        wl_inheritor_updated = true;
                } else {
                        filt_wlupdate_inheritor(kqwl, ts, TURNSTILE_IMMEDIATE_UPDATE);
                        wl_inheritor_updated = true;
                }

                /*
                 * We need a turnstile reference because we are dropping the interlock
                 * and the caller has not called turnstile_prepare.
                 */
                if (wl_inheritor_updated) {
                        turnstile_reference(ts);
                }
        }

        if (needs_wake && ts) {
                waitq_wakeup64_thread(&ts->ts_waitq, CAST_EVENT64_T((event_t)kn),
                                (thread_t)kn->kn_hook, THREAD_AWAKENED);
        }

        kq_req_unlock(kqwl);

        if (wl_inheritor_updated) {
                turnstile_update_inheritor_complete(ts, TURNSTILE_INTERLOCK_NOT_HELD);
                turnstile_deallocate(ts);
        }

out:
        /*
         * Phase 3:
         *
         * Unlock and cleanup various lingering references and things.
         */
        if (needs_wllock) {
                filt_wlunlock(kqwl);
        }

#if CONFIG_WORKLOOP_DEBUG
        KQWL_HISTORY_WRITE_ENTRY(kqwl, {
                .updater = current_thread(),
                .servicer = kqr->kqr_thread, /* Note: racy */
                .old_owner = cur_owner,
                .new_owner = new_owner,

                .kev_ident  = kev->ident,
                .error      = (int16_t)error,
                .kev_flags  = kev->flags,
                .kev_fflags = kev->fflags,

                .kev_mask   = mask,
                .kev_value  = kdata,
                .in_value   = udata,
        });
#endif // CONFIG_WORKLOOP_DEBUG

        if (cur_owner && new_owner != cur_owner) {
                if (cur_owner_override != THREAD_QOS_UNSPECIFIED) {
                        thread_drop_ipc_override(cur_owner);
                }
                thread_deallocate(cur_owner);
        }

        if (extra_thread_ref) {
                thread_deallocate(extra_thread_ref);
        }
        return error;
}

/*
 * 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
 */
static inline void
filt_wlremember_last_update(struct knote *kn, struct kevent_internal_s *kev,
                int error)
{
        kn->kn_fflags = kev->fflags;
        kn->kn_data = error;
        memcpy(kn->kn_ext, kev->ext, sizeof(kev->ext));
}

static int
filt_wlattach(struct knote *kn, struct kevent_internal_s *kev)
{
        struct kqueue *kq = knote_get_kq(kn);
        struct kqworkloop *kqwl = (struct kqworkloop *)kq;
        int error = 0;
        kq_index_t qos_index = 0;

        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;

                kq_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;
                }
                kev->ext[0] = thread_tid(kqwl->kqwl_owner);
                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];
                kq_req_unlock(kqwl);
                error = EBUSY;
                goto out;
        }
#endif

        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;
                        goto out;
                }
                qos_index = _pthread_priority_thread_qos(kn->kn_qos);
                if (qos_index == THREAD_QOS_UNSPECIFIED) {
                        error = ERANGE;
                        goto out;
                }
                if (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.
                         */
                        error = EALREADY;
                        goto out;
                }
                break;
        case NOTE_WL_SYNC_WAIT:
        case NOTE_WL_SYNC_WAKE:
                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;
        }

        error = filt_wlupdate(kqwl, kn, kev, qos_index, FILT_WLATTACH);

out:
        if (error) {
                /* If userland wants ESTALE to be hidden, fail the attach anyway */
                if (error == ESTALE && (kn->kn_sfflags & NOTE_WL_IGNORE_ESTALE)) {
                        error = 0;
                }
                knote_set_error(kn, error);
                return 0;
        }
        if (command == NOTE_WL_SYNC_WAIT) {
                return kevent_register_wait_prepare(kn, kev);
        }
        /* Just attaching the thread request successfully will fire it */
        if (command == NOTE_WL_THREAD_REQUEST) {
                /*
                 * Thread Request knotes need an explicit touch to be active again,
                 * so delivering an event needs to also consume it.
                 */
                kn->kn_flags |= EV_CLEAR;
                return FILTER_ACTIVE;
        }
        return 0;
}

static void __dead2
filt_wlwait_continue(void *parameter, wait_result_t wr)
{
        struct _kevent_register *cont_args = parameter;
        struct kqworkloop *kqwl = (struct kqworkloop *)cont_args->kq;
        struct kqrequest *kqr = &kqwl->kqwl_request;

        kq_req_lock(kqwl);
        kqr->kqr_dsync_waiters--;
        if (filt_wlturnstile_interlock_is_workq(kqwl)) {
                workq_kern_threadreq_lock(kqwl->kqwl_p);
                turnstile_complete((uintptr_t)kqwl, &kqwl->kqwl_turnstile, NULL);
                workq_kern_threadreq_unlock(kqwl->kqwl_p);
        } else {
                turnstile_complete((uintptr_t)kqwl, &kqwl->kqwl_turnstile, NULL);
        }
        kq_req_unlock(kqwl);

        turnstile_cleanup();

        if (wr == THREAD_INTERRUPTED) {
                cont_args->kev.flags |= EV_ERROR;
                cont_args->kev.data = EINTR;
        } else if (wr != THREAD_AWAKENED) {
                panic("Unexpected wait result: %d", wr);
        }

        kevent_register_wait_return(cont_args);
}

/*
 * Called with the workloop mutex held, most of the time never returns as it
 * calls filt_wlwait_continue through a continuation.
 */
static void __dead2
filt_wlpost_register_wait(struct uthread *uth, struct knote_lock_ctx *knlc,
                struct _kevent_register *cont_args)
{
        struct kqworkloop *kqwl = (struct kqworkloop *)cont_args->kq;
        struct kqrequest *kqr = &kqwl->kqwl_request;
        struct turnstile *ts;
        bool workq_locked = false;

        kq_req_lock(kqwl);

        kqr->kqr_dsync_waiters++;

        if (filt_wlturnstile_interlock_is_workq(kqwl)) {
                workq_kern_threadreq_lock(kqwl->kqwl_p);
                workq_locked = true;
        }

        ts = turnstile_prepare((uintptr_t)kqwl, &kqwl->kqwl_turnstile,
                        TURNSTILE_NULL, TURNSTILE_WORKLOOPS);

        if (workq_locked) {
                workq_kern_threadreq_update_inheritor(kqwl->kqwl_p,
                                &kqwl->kqwl_request, kqwl->kqwl_owner, ts,
                                TURNSTILE_DELAYED_UPDATE);
                if (!filt_wlturnstile_interlock_is_workq(kqwl)) {
                        /*
                         * if the interlock is no longer the workqueue lock,
                         * then we don't need to hold it anymore.
                         */
                        workq_kern_threadreq_unlock(kqwl->kqwl_p);
                        workq_locked = false;
                }
        }
        if (!workq_locked) {
                /*
                 * If the interlock is the workloop's, then it's our responsibility to
                 * call update_inheritor, so just do it.
                 */
                filt_wlupdate_inheritor(kqwl, ts, TURNSTILE_DELAYED_UPDATE);
        }

        thread_set_pending_block_hint(uth->uu_thread, kThreadWaitWorkloopSyncWait);
        waitq_assert_wait64(&ts->ts_waitq, CAST_EVENT64_T(cont_args->knote),
                        THREAD_ABORTSAFE, TIMEOUT_WAIT_FOREVER);

        if (workq_locked) {
                workq_kern_threadreq_unlock(kqwl->kqwl_p);
        }

        thread_t thread = kqwl->kqwl_owner ?: kqr->kqr_thread;
        if (thread) {
                thread_reference(thread);
        }
        kq_req_unlock(kqwl);

        kevent_register_wait_block(ts, thread, knlc, filt_wlwait_continue, cont_args);
}

/* 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"));

        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);

        struct kqworkloop *kqwl = (struct kqworkloop *)kq;
        struct kqrequest *kqr = &kqwl->kqwl_request;

        thread_t kqwl_owner = kqwl->kqwl_owner;
        thread_t servicer = kqr->kqr_thread;

        if (kqwl_owner != THREAD_NULL) {
                assert(kdp_is_in_zone(kqwl_owner, "threads"));

                waitinfo->owner = thread_tid(kqwl->kqwl_owner);
        } else if (servicer != THREAD_NULL) {
                assert(kdp_is_in_zone(servicer, "threads"));

                waitinfo->owner = thread_tid(servicer);
        } else if (kqr->kqr_state & KQR_THREQUESTED) {
                waitinfo->owner = STACKSHOT_WAITOWNER_THREQUESTED;
        } else {
                waitinfo->owner = 0;
        }

        waitinfo->context = kqwl->kqwl_dynamicid;
}

static void
filt_wldetach(__assert_only struct knote *kn)
{
        assert(knote_get_kq(kn)->kq_state & KQ_WORKLOOP);
        if (kn->kn_hook) {
                kevent_register_wait_cleanup(kn);
        }
}

static int
filt_wlvalidate_kev_flags(struct knote *kn, struct kevent_internal_s *kev,
                thread_qos_t *qos_index)
{
        int new_commands = kev->fflags & NOTE_WL_COMMANDS_MASK;
        int sav_commands = kn->kn_sfflags & NOTE_WL_COMMANDS_MASK;

        if ((kev->fflags & NOTE_WL_DISCOVER_OWNER) && (kev->flags & EV_DELETE)) {
                return EINVAL;
        }
        if (kev->fflags & NOTE_WL_UPDATE_QOS) {
                if (kev->flags & EV_DELETE) {
                        return EINVAL;
                }
                if (sav_commands != NOTE_WL_THREAD_REQUEST) {
                        return EINVAL;
                }
                if (!(*qos_index = _pthread_priority_thread_qos(kev->qos))) {
                        return ERANGE;
                }
        }

        switch (new_commands) {
        case NOTE_WL_THREAD_REQUEST:
                /* thread requests can only update themselves */
                if (sav_commands != NOTE_WL_THREAD_REQUEST)
                        return EINVAL;
                break;

        case NOTE_WL_SYNC_WAIT:
                if (kev->fflags & NOTE_WL_END_OWNERSHIP)
                        return EINVAL;
                goto sync_checks;

        case NOTE_WL_SYNC_WAKE:
        sync_checks:
                if (!(sav_commands & (NOTE_WL_SYNC_WAIT | NOTE_WL_SYNC_WAKE)))
                        return EINVAL;
                if ((kev->flags & (EV_ENABLE | EV_DELETE)) == EV_ENABLE)
                        return EINVAL;
                break;

        default:
                return EINVAL;
        }
        return 0;
}

static int
filt_wltouch(struct knote *kn, struct kevent_internal_s *kev)
{
        struct kqworkloop *kqwl = (struct kqworkloop *)knote_get_kq(kn);
        thread_qos_t qos_index = THREAD_QOS_UNSPECIFIED;

        int error = filt_wlvalidate_kev_flags(kn, kev, &qos_index);
        if (error) {
                goto out;
        }

        error = filt_wlupdate(kqwl, kn, kev, qos_index, FILT_WLTOUCH);
        filt_wlremember_last_update(kn, kev, error);
        if (error) {
                goto out;
        }

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;
        }
        int command = kev->fflags & NOTE_WL_COMMANDS_MASK;
        if (command == NOTE_WL_SYNC_WAIT && !(kn->kn_sfflags & NOTE_WL_SYNC_WAKE)) {
                return kevent_register_wait_prepare(kn, kev);
        }
        /* Just touching the thread request successfully will fire it */
        if (command == NOTE_WL_THREAD_REQUEST) {
                if (kev->fflags & NOTE_WL_UPDATE_QOS) {
                        return FILTER_ACTIVE | FILTER_UPDATE_REQ_QOS;
                }
                return FILTER_ACTIVE;
        }
        return 0;
}

static bool
filt_wlallow_drop(struct knote *kn, struct kevent_internal_s *kev)
{
        struct kqworkloop *kqwl = (struct kqworkloop *)knote_get_kq(kn);

        int error = filt_wlvalidate_kev_flags(kn, kev, NULL);
        if (error) {
                goto out;
        }

        error = filt_wlupdate(kqwl, kn, kev, 0, FILT_WLDROP);
        filt_wlremember_last_update(kn, kev, error);
        if (error) {
                goto out;
        }

out:
        if (error) {
                if (error == ESTALE && (kev->fflags & NOTE_WL_IGNORE_ESTALE)) {
                        return false;
                }
                kev->flags |= EV_ERROR;
                kev->data = error;
                return false;
        }
        return true;
}

static int
filt_wlprocess(
        struct knote *kn,
        __unused struct filt_process_s *data,
        struct kevent_internal_s *kev)
{
        struct kqworkloop *kqwl = (struct kqworkloop *)knote_get_kq(kn);
        int rc = 0;

        assert(kn->kn_sfflags & NOTE_WL_THREAD_REQUEST);

        filt_wllock(kqwl);

        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(kqwl);
                knote_activate(kn);
                kqunlock(kqwl);
        } else {
#if DEBUG || DEVELOPMENT
                if (kevent_debug_flags() & KEVENT_PANIC_ON_NON_ENQUEUED_PROCESS) {
                        /*
                         * see src/queue_internal.h in libdispatch
                         */
#define DISPATCH_QUEUE_ENQUEUED 0x1ull
                        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) != 0xdead && (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 |= FILTER_ACTIVE;
        }

        filt_wlunlock(kqwl);

        if (rc & FILTER_ACTIVE) {
                workq_thread_set_max_qos(kqwl->kqwl_p, &kqwl->kqwl_request);
        }
        return rc;
}

SECURITY_READ_ONLY_EARLY(static struct filterops) workloop_filtops = {
        .f_extended_codes = true,
        .f_attach  = filt_wlattach,
        .f_detach  = filt_wldetach,
        .f_event   = filt_badevent,
        .f_touch   = filt_wltouch,
        .f_process = filt_wlprocess,
        .f_allow_drop = filt_wlallow_drop,
        .f_post_register_wait = filt_wlpost_register_wait,
};

#pragma mark kevent / knotes

/*
 * JMM - placeholder for not-yet-implemented filters
 */
static int
filt_badevent(struct knote *kn, long hint)
{
        panic("%s[%d](%p, %ld)", __func__, kn->kn_filter, kn, hint);
        return 0;
}

static int
filt_badattach(__unused struct knote *kn, __unused struct kevent_internal_s *kev)
{
        knote_set_error(kn, ENOTSUP);
        return 0;
}

struct kqueue *
kqueue_alloc(struct proc *p, unsigned int flags)
{
        struct filedesc *fdp = p->p_fd;
        struct kqueue *kq = NULL;
        int policy;
        void *hook = NULL;

        if (flags & KEVENT_FLAG_WORKQ) {
                struct kqworkq *kqwq;
                int i;

                kqwq = (struct kqworkq *)zalloc(kqworkq_zone);
                if (kqwq == NULL)
                        return NULL;

                kq = &kqwq->kqwq_kqueue;
                bzero(kqwq, sizeof (struct kqworkq));

                kqwq->kqwq_state = KQ_WORKQ;

                for (i = 0; i < KQWQ_NBUCKETS; i++) {
                        TAILQ_INIT(&kqwq->kqwq_queue[i]);
                }
                for (i = 0; i < KQWQ_NBUCKETS; i++) {
                        if (i != KQWQ_QOS_MANAGER) {
                                /*
                                 * Because of how the bucketized system works, we mix overcommit
                                 * sources with not overcommit: each time we move a knote from
                                 * one bucket to the next due to overrides, we'd had to track
                                 * overcommitness, and it's really not worth it in the workloop
                                 * enabled world that track this faithfully.
                                 *
                                 * Incidentally, this behaves like the original manager-based
                                 * kqwq where event delivery always happened (hence is
                                 * "overcommit")
                                 */
                                kqwq->kqwq_request[i].kqr_state |= KQR_THOVERCOMMIT;
                        }
                        kqwq->kqwq_request[i].kqr_qos_index = i;
                        TAILQ_INIT(&kqwq->kqwq_request[i].kqr_suppressed);
                }

                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 */
                kqwl->kqwl_request.kqr_state = KQR_WORKLOOP;

                kq = &kqwl->kqwl_kqueue;
                for (i = 0; i < KQWL_NBUCKETS; i++) {
                        TAILQ_INIT(&kqwl->kqwl_queue[i]);
                }
                TAILQ_INIT(&kqwl->kqwl_request.kqr_suppressed);

                lck_mtx_init(&kqwl->kqwl_statelock, kq_lck_grp, kq_lck_attr);

                policy = SYNC_POLICY_FIFO;
                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(&kqf->kqf_queue);
                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);
        lck_spin_init(&kq->kq_reqlock, 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);
        }

        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);
                                knote_drop(kq, kn, NULL);
                                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);
                                knote_drop(kq, kn, NULL);
                                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);
}

/*
 * kqworkloop_invalidate
 *
 * Invalidate ownership of a workloop.
 *
 * This is meant to be used so that any remnant of overrides and ownership
 * information is dropped before a kqworkloop can no longer be found in the
 * global hash table and have ghost workloop ownership left over.
 *
 * Possibly returns a thread to deallocate in a safe context.
 */
static thread_t
kqworkloop_invalidate(struct kqworkloop *kqwl)
{
        thread_t cur_owner = kqwl->kqwl_owner;

        assert(TAILQ_EMPTY(&kqwl->kqwl_request.kqr_suppressed));
        if (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 (kqworkloop_owner_override(kqwl) != THREAD_QOS_UNSPECIFIED) {
                        thread_drop_ipc_override(cur_owner);
                }
                thread_ends_owning_workloop(cur_owner);
                kqwl->kqwl_owner = THREAD_NULL;
        }

        return cur_owner;
}

/*
 * 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;

        /*
         * Workloops are refcounted by their knotes, so there's no point
         * spending a lot of time under these locks just to deallocate one.
         */
        if ((kq->kq_state & KQ_WORKLOOP) == 0) {
                KNOTE_LOCK_CTX(knlc);

                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)) {
                                        kqlock(kq);
                                        proc_fdunlock(p);
                                        if (knote_lock(kq, kn, &knlc, KNOTE_KQ_LOCK_ON_SUCCESS)) {
                                                knote_drop(kq, kn, &knlc);
                                        }
                                        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)) {
                                                kqlock(kq);
                                                knhash_unlock(p);
                                                if (knote_lock(kq, kn, &knlc, KNOTE_KQ_LOCK_ON_SUCCESS)) {
                                                        knote_drop(kq, kn, &knlc);
                                                }
                                                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;
                thread_t cur_owner = kqworkloop_invalidate(kqwl);

                if (cur_owner) thread_deallocate(cur_owner);

                if (kqwl->kqwl_request.kqr_state & KQR_ALLOCATED_TURNSTILE) {
                        struct turnstile *ts;
                        turnstile_complete((uintptr_t)kqwl, &kqwl->kqwl_turnstile, &ts);
                        turnstile_cleanup();
                        turnstile_deallocate(ts);
                } else {
                        assert(kqwl->kqwl_turnstile == 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);
        lck_spin_destroy(&kq->kq_reqlock, kq_lck_grp);

        if (kq->kq_state & KQ_WORKQ) {
                zfree(kqworkq_zone, (struct kqworkq *)kq);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                struct kqworkloop *kqwl = (struct kqworkloop *)kq;

                assert(kqwl->kqwl_retains == 0);
                lck_mtx_destroy(&kqwl->kqwl_statelock, kq_lck_grp);
                zfree(kqworkloop_zone, kqwl);
        } else {
                zfree(kqfile_zone, (struct kqfile *)kq);
        }
}

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(kqueue_t kqu, __assert_only int possibly_last)
{
        if ((kqu.kq->kq_state & KQ_DYNAMIC) == 0) {
                return 0;
        }

        assert(kqu.kq->kq_state & KQ_WORKLOOP); /* for now */
        uint32_t refs = OSDecrementAtomic(&kqu.kqwl->kqwl_retains);
        if (__improbable(refs == 0)) {
                panic("kq(%p) over-release", kqu.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, kqueue_t kqu)
{
        struct kqueue *kq = kqu.kq;
        if (kq->kq_state & KQ_DYNAMIC) {
                kqhash_lock(p);
                if (kqueue_release(kq, KQUEUE_MIGHT_BE_LAST_REF)) {
                        thread_t cur_owner = kqworkloop_invalidate(kqu.kqwl);
                        kqueue_hash_remove(p, kq);
                        kqhash_unlock(p);
                        if (cur_owner) thread_deallocate(cur_owner);
                        kqueue_dealloc(kq);
                } else {
                        kqhash_unlock(p);
                }
        }
}

/*
 * kqworkloops_dealloc - rebalance retains on kqworkloops created with
 * scheduling parameters
 *
 *              Called with proc_fdlock held.
 *              Returns with it locked.
 *              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
kqworkloops_dealloc(proc_t p)
{
        struct filedesc *fdp = p->p_fd;
        struct kqlist *list;
        struct kqworkloop *kqwl, *kqwln;
        struct kqlist tofree;
        int i;

        if (!(fdp->fd_flags & FD_WORKLOOP)) {
                return;
        }

        SLIST_INIT(&tofree);

        kqhash_lock(p);
        assert(fdp->fd_kqhashmask != 0);

        for (i = 0; i <= (int)fdp->fd_kqhashmask; i++) {
                list = &fdp->fd_kqhash[i];
                SLIST_FOREACH_SAFE(kqwl, list, kqwl_hashlink, kqwln) {
                        /*
                         * kqworkloops that have scheduling parameters have an
                         * implicit retain from kqueue_workloop_ctl that needs
                         * to be balanced on process exit.
                         */
                        assert(kqwl->kqwl_params);
                        SLIST_REMOVE(list, kqwl, kqworkloop, kqwl_hashlink);
                        SLIST_INSERT_HEAD(&tofree, kqwl, kqwl_hashlink);
                }
        }

        kqhash_unlock(p);

        SLIST_FOREACH_SAFE(kqwl, &tofree, kqwl_hashlink, kqwln) {
                struct kqueue *kq = (struct kqueue *)kqwl;
                __assert_only bool released;
                released = kqueue_release(kq, KQUEUE_MIGHT_BE_LAST_REF);
                assert(released);
                kqueue_dealloc(kq);
        }
}

static struct kqueue *
kevent_get_bound_kqworkloop(thread_t thread)
{
        struct uthread *ut = get_bsdthread_info(thread);
        struct kqrequest *kqr = ut->uu_kqr_bound;

        return kqr ? (struct kqueue *)kqr_kqworkloop(kqr) : NULL;
}

static int
kevent_get_kq(struct proc *p, kqueue_id_t id, workq_threadreq_param_t *trp,
                unsigned int flags, struct fileproc **fpp, int *fdp,
                struct kqueue **kqp)
{
        struct filedesc *descp = p->p_fd;
        struct fileproc *fp = NULL;
        struct kqueue *kq = NULL;
        int fd = 0;
        int error = 0;
        thread_t th = current_thread();

        assert(!trp || (flags & KEVENT_FLAG_WORKLOOP));

        /* Was the workloop flag passed?  Then it is for sure only a workloop */
        if (flags & KEVENT_FLAG_DYNAMIC_KQUEUE) {
                assert(flags & KEVENT_FLAG_WORKLOOP);
                assert(!trp || (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST));
                kq = kevent_get_bound_kqworkloop(th);

                /*
                 * 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.
                 */
                if (id == (kqueue_id_t)-1 &&
                    (flags & KEVENT_FLAG_KERNEL) &&
                    (flags & KEVENT_FLAG_WORKLOOP)) {

                        if (!is_workqueue_thread(th) || !kq) {
                                return EINVAL;
                        }

                        kqueue_retain(kq);
                        goto out;
                }

                if (id == 0 || id == (kqueue_id_t)-1) {
                        return EINVAL;
                }

                /* try shortcut on kq lookup for bound threads */
                if (kq != NULL && ((struct kqworkloop *)kq)->kqwl_dynamicid == id) {

                        if (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST) {
                                return EEXIST;
                        }

                        /* retain a reference while working with this kq. */
                        assert(kq->kq_state & KQ_DYNAMIC);
                        kqueue_retain(kq);
                        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) {
                                return ENOENT;
                        }

                        struct kqueue *alloc_kq;
                        alloc_kq = kqueue_alloc(p, flags);
                        if (!alloc_kq) {
                                return ENOMEM;
                        }

                        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;
                                if (trp) {
                                        struct kqworkloop *kqwl = (struct kqworkloop *)kq;
                                        kqwl->kqwl_params = trp->trp_value;
                                }
                                kqueue_hash_insert(p, id, kq);
                                kqhash_unlock(p);
                        } else if (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST) {
                                /* lost race and caller wants an error */
                                kqhash_unlock(p);
                                kqueue_release(alloc_kq, KQUEUE_MIGHT_BE_LAST_REF);
                                kqueue_dealloc(alloc_kq);
                                return EEXIST;
                        } 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 {

                        if (flags & KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST) {
                                kqhash_unlock(p);
                                return  EEXIST;
                        }

                        /* 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 = OS_REASON_NULL;
        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);

        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;
        }

        if (workloop_id) {
                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
        if (kevent_debug_flags() & KEVENT_PANIC_ON_WORKLOOP_OWNERSHIP_LEAK) {
                panic("thread %p in task %p is leaked workloop 0x%016llx ownership",
                                thread, p->task, workloop_id);
        }
        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 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)
{
        uthread_t ut;
        struct kqueue *kq;
        struct fileproc *fp = NULL;
        int fd = 0;
        struct kevent_internal_s kev;
        int error, noutputs, register_rc;
        bool needs_end_processing = false;
        struct timeval atv;
        user_size_t data_size;
        user_size_t data_resid;
        thread_t thread = current_thread();
        KNOTE_LOCK_CTX(knlc);

        /* 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;

        if (flags & KEVENT_FLAG_PARKING) {
                if (!kevent_args_requesting_events(flags, nevents) || id != (kqueue_id_t)-1)
                        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)) && (flags & (KEVENT_FLAG_WORKQ)))
                return EINVAL;

        if (flags & (KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST | KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST)) {

                /* 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;
        }

        /* 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, NULL, flags, &fp, &fd, &kq);
#if CONFIG_WORKLOOP_DEBUG
        ut = (uthread_t)get_bsdthread_info(thread);
        UU_KEVENT_HISTORY_WRITE_ENTRY(ut, {
                .uu_kqid = id,
                .uu_kq = error ? NULL : kq,
                .uu_error = error,
                .uu_nchanges = nchanges,
                .uu_nevents = nevents,
                .uu_flags = flags,
        });
#endif // CONFIG_WORKLOOP_DEBUG
        if (error)
                return error;

        /* only bound threads can receive events on workloops */
        if (flags & KEVENT_FLAG_WORKLOOP) {
                struct kqworkloop *kqwl = (struct kqworkloop *)kq;
                struct kqrequest *kqr = &kqwl->kqwl_request;

                assert(kq->kq_state & KQ_WORKLOOP);

                if (kevent_args_requesting_events(flags, nevents)) {
                        if (kq != kevent_get_bound_kqworkloop(thread)) {
                                error = EXDEV;
                                goto out;
                        }

                        kq_req_lock(kqwl);
                        /*
                         * Disable the R2K notification while doing a register, if the
                         * caller wants events too, we don't want the AST to be set if we
                         * will process these events soon.
                         */
                        kqr->kqr_state &= ~KQR_R2K_NOTIF_ARMED;
                        needs_end_processing = true;
                        kq_req_unlock(kq);
                }

                if (id_out) {
                        *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;

                register_rc = kevent_register(kq, &kev, &knlc);
                if (register_rc & FILTER_REGISTER_WAIT) {
                        kqlock_held(kq);

                        // f_post_register_wait is meant to call a continuation and not to
                        // return, which is why we don't support FILTER_REGISTER_WAIT if
                        // KEVENT_FLAG_ERROR_EVENTS is not passed, or if the event that
                        // waits isn't the last.
                        //
                        // It is implementable, but not used by any userspace code at the
                        // moment, so for now return ENOTSUP if someone tries to do it.
                        if (nchanges == 1 && nevents >= 1 && (flags & KEVENT_FLAG_ERROR_EVENTS)) {
                                struct _kevent_register *cont_args;
                                /* store the continuation/completion data in the uthread */
                                ut = (uthread_t)get_bsdthread_info(thread);
                                cont_args = &ut->uu_save.uus_kevent_register;
                                cont_args->kev = kev;
                                cont_args->kq = kq;
                                cont_args->fp = fp;
                                cont_args->fd = fd;
                                cont_args->ueventlist = ueventlist;
                                cont_args->flags = flags;
                                cont_args->retval = retval;
                                cont_args->eventcount = nevents;
                                cont_args->eventout = noutputs;
                                knote_fops(cont_args->knote)->f_post_register_wait(ut, &knlc, cont_args);
                                panic("f_post_register_wait returned (kev: %p)", &kev);
                        }

                        kev.flags |= EV_ERROR;
                        kev.data = ENOTSUP;
                        knote_unlock(kq, knlc.knlc_knote, &knlc, KNOTE_KQ_UNLOCK);
                }

                // keep in sync with kevent_register_wait_return()
                if (nevents > 0 && (kev.flags & (EV_ERROR|EV_RECEIPT))) {
                        if ((kev.flags & EV_ERROR) == 0) {
                                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) {
                struct _kevent *cont_args;
                /* store the continuation/completion data in the uthread */
                ut = (uthread_t)get_bsdthread_info(thread);
                cont_args = &ut->uu_save.uus_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;

                /*
                 * kqworkloop_end_processing() will happen at the end of kqueue_scan()
                 */
                needs_end_processing = false;

                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);
                }
        }

out:
        if (__improbable(needs_end_processing)) {
                /*
                 * If we didn't through kqworkloop_end_processing(),
                 * we need to do it here.
                 */
                kqlock(kq);
                kqworkloop_end_processing((struct kqworkloop *)kq, 0, 0);
                kqunlock(kq);
        }
        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);
}

static int
kevent_register_validate_priority(struct kqueue *kq, struct knote *kn,
                struct kevent_internal_s *kev)
{
        /* We don't care about the priority of a disabled or deleted knote */
        if (kev->flags & (EV_DISABLE | EV_DELETE)) {
                return 0;
        }

        if (kq->kq_state & KQ_WORKLOOP) {
                /*
                 * Workloops need valid priorities with a QOS (excluding manager) for
                 * any enabled knote.
                 *
                 * When it is pre-existing, just make sure it has a valid QoS as
                 * kevent_register() will not use the incoming priority (filters who do
                 * have the responsibility to validate it again, see filt_wltouch).
                 *
                 * If the knote is being made, validate the incoming priority.
                 */
                if (!_pthread_priority_thread_qos(kn ? kn->kn_qos : kev->qos)) {
                        return ERANGE;
                }
        }

        return 0;
}

/*
 * Prepare a filter for waiting after register.
 *
 * The f_post_register_wait hook will be called later by kevent_register()
 * and should call kevent_register_wait_block()
 */
static int
kevent_register_wait_prepare(struct knote *kn, struct kevent_internal_s *kev)
{
        thread_t thread = current_thread();
        struct uthread *uth = get_bsdthread_info(thread);

        assert(knote_fops(kn)->f_extended_codes);

        if (kn->kn_hook == NULL) {
                thread_reference(thread);
                kn->kn_hook = thread;
        } else if (kn->kn_hook != thread) {
                /*
                 * kn_hook may be set from a previous aborted wait
                 * However, it has to be from the same thread.
                 */
                kev->flags |= EV_ERROR;
                kev->data = EXDEV;
                return 0;
        }

        uth->uu_save.uus_kevent_register.knote = kn;
        return FILTER_REGISTER_WAIT;
}

/*
 * Cleanup a kevent_register_wait_prepare() effect for threads that have been
 * aborted instead of properly woken up with thread_wakeup_thread().
 */
static void
kevent_register_wait_cleanup(struct knote *kn)
{
        thread_t thread = kn->kn_hook;
        kn->kn_hook = NULL;
        thread_deallocate(thread);
}

/*
 * Must be called at the end of a f_post_register_wait call from a filter.
 */
static void
kevent_register_wait_block(struct turnstile *ts, thread_t thread,
                struct knote_lock_ctx *knlc, thread_continue_t cont,
                struct _kevent_register *cont_args)
{
        knote_unlock(cont_args->kq, cont_args->knote, knlc, KNOTE_KQ_UNLOCK);
        turnstile_update_inheritor_complete(ts, TURNSTILE_INTERLOCK_NOT_HELD);
        cont_args->handoff_thread = thread;
        thread_handoff_parameter(thread, cont, cont_args);
}

/*
 * Called by Filters using a f_post_register_wait to return from their wait.
 */
static void
kevent_register_wait_return(struct _kevent_register *cont_args)
{
        struct kqueue *kq = cont_args->kq;
        proc_t p = kq->kq_p;
        struct kevent_internal_s *kev = &cont_args->kev;
        int error = 0;

        if (cont_args->handoff_thread) {
                thread_deallocate(cont_args->handoff_thread);
        }

        if (kev->flags & (EV_ERROR|EV_RECEIPT)) {
                if ((kev->flags & EV_ERROR) == 0) {
                        kev->flags |= EV_ERROR;
                        kev->data = 0;
                }
                error = kevent_copyout(kev, &cont_args->ueventlist, p, cont_args->flags);
                if (error == 0) cont_args->eventout++;
        }

        kevent_put_kq(p, cont_args->fd, cont_args->fp, kq);
        if (error == 0) {
                *cont_args->retval = cont_args->eventout;
        }
        unix_syscall_return(error);
}

/*
 * 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
 */

int
kevent_register(struct kqueue *kq, struct kevent_internal_s *kev,
                struct knote_lock_ctx *knlc)
{
        struct proc *p = kq->kq_p;
        const struct filterops *fops;
        struct knote *kn = NULL;
        int result = 0, error = 0;
        unsigned short kev_flags = kev->flags;

        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);
        error = kevent_register_validate_priority(kq, kn, kev);
        result = 0;
        if (error) {
                goto out;
        }

        if (kn == NULL && (kev->flags & EV_ADD) == 0) {
                /*
                 * No knote found, EV_ADD wasn't specified
                 */

                if ((kev_flags & EV_ADD) && (kev_flags & 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 if (kn == NULL) {
                /*
                 * No knote found, need to attach a new one (attach)
                 */

                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;
                kn->kn_kq_packed = (intptr_t)(struct kqueue *)kq;
                kqueue_retain(kq); /* retain a kq ref */
                kn->kn_filtid = ~kev->filter;
                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;
                if (kev->flags & EV_DISABLE)
                        kn->kn_status |= KN_DISABLED;

                /*
                 * 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;
                knote_reset_priority(kn, kev->qos);

                /* Add the knote for lookup thru the fd table */
                error = kq_add_knote(kq, kn, knlc, p);
                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) {
                                goto restart;
                        }
                        goto out;
                }

                /* fp reference count now applies to knote */

                /*
                 * we can't use filter_call() because f_attach can change the filter ops
                 * for a filter that supports f_extended_codes, so we need to reload
                 * knote_fops() and not use `fops`.
                 */
                result = fops->f_attach(kn, kev);
                if (result && !knote_fops(kn)->f_extended_codes) {
                        result = FILTER_ACTIVE;
                }

                kqlock(kq);

                if (kn->kn_flags & EV_ERROR) {
                        /*
                         * Failed to attach correctly, so drop.
                         */
                        kn->kn_status &= ~(KN_ATTACHED | KN_ATTACHING);
                        error = kn->kn_data;
                        knote_drop(kq, kn, knlc);
                        result = 0;
                        goto out;
                }

                /*
                 * end "attaching" phase - now just attached
                 *
                 * Mark the thread request overcommit, if appropos
                 *
                 * If the attach routine indicated that an
                 * event is already fired, activate the knote.
                 */
                kn->kn_status &= ~KN_ATTACHING;
                knote_set_qos_overcommit(kn);

                if (result & FILTER_ACTIVE) {
                        if (result & FILTER_ADJUST_EVENT_QOS_BIT)
                                knote_adjust_qos(kq, kn, result);
                        knote_activate(kn);
                }

        } else if (!knote_lock(kq, kn, knlc, KNOTE_KQ_LOCK_ON_SUCCESS)) {

                /*
                 * The knote was dropped while we were waiting for the lock,
                 * we need to re-evaluate entirely
                 */

                goto restart;

        } else if (kev->flags & EV_DELETE) {
                /*
                 * Deletion of a knote (drop)
                 *
                 * If the filter wants to filter drop events, let it do so.
                 *
                 * defer-delete: when trying to delete a disabled EV_DISPATCH2 knote,
                 * we must wait for the knote to be re-enabled (unless it is being
                 * re-enabled atomically here).
                 */

                if (knote_fops(kn)->f_allow_drop) {
                        bool drop;

                        kqunlock(kq);
                        drop = knote_fops(kn)->f_allow_drop(kn, kev);
                        kqlock(kq);

                        if (!drop) goto out_unlock;
                }

                if ((kev->flags & EV_ENABLE) == 0 &&
                                (kn->kn_status & (KN_DISPATCH2 | KN_DISABLED)) ==
                                (KN_DISPATCH2 | KN_DISABLED)) {
                        kn->kn_status |= KN_DEFERDELETE;
                        error = EINPROGRESS;
                        goto out_unlock;
                }

                knote_drop(kq, kn, knlc);
                goto out;

        } else {
                /*
                 * Regular update of a knote (touch)
                 *
                 * Call touch routine to notify filter of changes in filter values
                 * (and to re-determine if any events are fired).
                 *
                 * If the knote is in defer-delete, avoid calling the filter touch
                 * routine (it has delivered its last event already).
                 *
                 * If the touch routine had no failure,
                 * apply the requested side effects to the knote.
                 */

                if (kn->kn_status & (KN_DEFERDELETE | KN_VANISHED)) {
                        if (kev->flags & EV_ENABLE) {
                                result = FILTER_ACTIVE;
                        }
                } else {
                        kqunlock(kq);
                        result = filter_call(knote_fops(kn), f_touch(kn, kev));
                        kqlock(kq);
                }

                if (kev->flags & EV_ERROR) {
                        result = 0;
                } else {
                        /* accept new kevent state */
                        if ((kn->kn_status & KN_UDATA_SPECIFIC) == 0)
                                kn->kn_udata = kev->udata;
                        if (kev->flags & EV_DISABLE)
                                knote_disable(kn);
                        if (result & (FILTER_UPDATE_REQ_QOS | FILTER_ADJUST_EVENT_QOS_BIT))
                                knote_dequeue(kn);
                        if ((result & FILTER_UPDATE_REQ_QOS) &&
                                        kev->qos && kev->qos != kn->kn_qos) {
                                knote_reset_priority(kn, kev->qos);
                        }
                        if (result & FILTER_ACTIVE) {
                                thread_qos_t qos;
                                if (result & FILTER_ADJUST_EVENT_QOS_BIT) {
                                        if (knote_should_apply_qos_override(kq, kn, result, &qos)) {
                                                knote_apply_qos_override(kn, qos);
                                        }
                                }
                                knote_activate(kn);
                        }
                        if (result & (FILTER_UPDATE_REQ_QOS | FILTER_ADJUST_EVENT_QOS_BIT)) {
                                if (knote_enqueue(kn) && (kn->kn_status & KN_ACTIVE)) {
                                        knote_wakeup(kn);
                                }
                        }
                        if (kev->flags & EV_ENABLE)
                                knote_enable(kn);
                }
        }

out_unlock:
        if ((result & FILTER_REGISTER_WAIT) == 0) {
                /*
                 * When the filter asked for a post-register wait,
                 * we leave the knote and kqueue locked for kevent_register()
                 * to call the filter's f_post_register_wait hook.
                 */
                knote_unlock(kq, kn, knlc, KNOTE_KQ_UNLOCK);
        }

out:
        /* output local errors through the kevent */
        if (error) {
                kev->flags |= EV_ERROR;
                kev->data = error;
        }
        return result;
}

/*
 * 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 kevent_internal_s kev;
        struct kqueue *kq = knote_get_kq(kn);
        KNOTE_LOCK_CTX(knlc);
        int result = FILTER_ACTIVE;
        int error = 0;
        bool drop = false;

        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);
        }

        if ((kn->kn_status & KN_DROPPING) ||
                        !knote_lock(kq, kn, &knlc, KNOTE_KQ_LOCK_ALWAYS)) {
                /*
                 * When the knote is dropping or has dropped,
                 * then there's nothing we want to process.
                 */
                return EJUSTRETURN;
        }

        /*
         * 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.
         *
         * suppress knotes to avoid returning the same event multiple times in
         * a single call.
         */
        knote_suppress(kn);

        if (kn->kn_status & (KN_DEFERDELETE | KN_VANISHED)) {
                /* create fake event */
                kev.filter = kn->kn_filter;
                kev.ident = kn->kn_id;
                kev.flags = (kn->kn_status & KN_DEFERDELETE) ? EV_DELETE : EV_VANISHED;
                kev.flags |= (EV_DISPATCH2 | EV_ONESHOT);
                kev.udata = kn->kn_udata;
        } else {
                /* deactivate - so new activations indicate a wakeup */
                knote_deactivate(kn);

                kqunlock(kq);
                result = filter_call(knote_fops(kn), f_process(kn, process_data, &kev));
                kqlock(kq);
        }

        /*
         * 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.
         * 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 & FILTER_ACTIVE) == 0) {
                if ((kn->kn_status & (KN_ACTIVE | KN_STAYACTIVE)) == 0) {
                        /*
                         * Stay active knotes should not be unsuppressed or we'd create an
                         * infinite loop.
                         *
                         * Some knotes (like EVFILT_WORKLOOP) can be reactivated from
                         * within f_process() but that doesn't necessarily make them
                         * ready to process, so we should leave them be.
                         *
                         * For other knotes, since we will not return an event,
                         * there's no point keeping the knote suppressed.
                         */
                        knote_unsuppress(kn);
                }
                knote_unlock(kq, kn, &knlc, KNOTE_KQ_LOCK_ALWAYS);
                return EJUSTRETURN;
        }

        if (result & FILTER_ADJUST_EVENT_QOS_BIT)
                knote_adjust_qos(kq, kn, result);
        kev.qos = _pthread_priority_combine(kn->kn_qos, kn->kn_qos_override);

        if (kev.flags & EV_ONESHOT) {
                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);
                } else {
                        drop = true;
                }
        } 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 (drop) {
                knote_drop(kq, kn, &knlc);
        } else {
                knote_unlock(kq, kn, &knlc, KNOTE_KQ_UNLOCK);
        }

        if (kev.flags & EV_VANISHED) {
                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KNOTE_VANISHED),
                              kev.ident, kn->kn_udata, kn->kn_status | (kn->kn_id << 32),
                              kn->kn_filtid);
        }

        error = (callback)(kq, &kev, callback_data);
        kqlock(kq);
        return error;
}

/*
 * Returns -1 if the kqueue was unbound and processing should not happen
 */
#define KQWQAE_BEGIN_PROCESSING 1
#define KQWQAE_END_PROCESSING   2
#define KQWQAE_UNBIND           3
static int
kqworkq_acknowledge_events(struct kqworkq *kqwq, struct kqrequest *kqr,
                int kevent_flags, int kqwqae_op)
{
        thread_qos_t old_override = THREAD_QOS_UNSPECIFIED;
        thread_t thread = kqr->kqr_thread;
        struct knote *kn;
        int rc = 0;
        bool seen_stayactive = false, unbind;

        kqlock_held(&kqwq->kqwq_kqueue);

        if (!TAILQ_EMPTY(&kqr->kqr_suppressed)) {
                /*
                 * 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(&kqr->kqr_suppressed)) != NULL) {
                        assert(kn->kn_status & KN_SUPPRESSED);
                        knote_unsuppress(kn);
                        if (kn->kn_status & KN_STAYACTIVE) {
                                seen_stayactive = true;
                        }
                }
        }

        kq_req_lock(kqwq);

#if DEBUG || DEVELOPMENT
        thread_t self = current_thread();
        struct uthread *ut = get_bsdthread_info(self);

        assert(kqr->kqr_state & KQR_THREQUESTED);
        assert(kqr->kqr_thread == self);
        assert(ut->uu_kqr_bound == kqr);
#endif // DEBUG || DEVELOPMENT

        if (kqwqae_op == KQWQAE_UNBIND) {
                unbind = true;
        } else if ((kevent_flags & KEVENT_FLAG_PARKING) == 0) {
                unbind = false;
        } else if (kqwqae_op == KQWQAE_BEGIN_PROCESSING && seen_stayactive) {
                /*
                 * When we unsuppress stayactive knotes, for the kind that are hooked
                 * through select, we need to process once before we can assert there's
                 * no event pending. Hence we can't unbind during BEGIN PROCESSING.
                 */
                unbind = false;
        } else {
                unbind = ((kqr->kqr_state & KQR_WAKEUP) == 0);
        }
        if (unbind) {
                old_override = kqworkq_unbind_locked(kqwq, kqr, thread);
                rc = -1;
                /*
                 * 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) {
                        kqueue_threadreq_initiate(&kqwq->kqwq_kqueue, kqr,
                                        kqr->kqr_qos_index, 0);
                }
        }

        if (rc == 0) {
                /*
                 * Reset wakeup bit to notice events firing while we are processing,
                 * as we cannot rely on the bucket queue emptiness because of stay
                 * active knotes.
                 */
                kqr->kqr_state &= ~KQR_WAKEUP;
        }

        kq_req_unlock(kqwq);

        if (old_override) {
                thread_drop_ipc_override(thread);
        }

        return rc;
}

/*
 * 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, struct kqrequest *kqr,
                int kevent_flags)
{
        int rc = 0;

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_PROCESS_BEGIN) | DBG_FUNC_START,
                        0, kqr->kqr_qos_index);

        rc = kqworkq_acknowledge_events(kqwq, kqr, kevent_flags,
                        KQWQAE_BEGIN_PROCESSING);

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_PROCESS_BEGIN) | DBG_FUNC_END,
                        thread_tid(kqr->kqr_thread), kqr->kqr_state);

        return rc;
}

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 thread_qos_t
kqworkloop_acknowledge_events(struct kqworkloop *kqwl)
{
        struct kqrequest *kqr = &kqwl->kqwl_request;
        kq_index_t qos = THREAD_QOS_UNSPECIFIED;
        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) {
                        qos = MAX(qos, knote_get_qos_override_index(kn));
                        continue;
                }
                knote_unsuppress(kn);
        }

        return qos;
}

static int
kqworkloop_begin_processing(struct kqworkloop *kqwl, unsigned int kevent_flags)
{
        struct kqrequest *kqr = &kqwl->kqwl_request;
        struct kqueue *kq = &kqwl->kqwl_kqueue;
        thread_qos_t old_override = THREAD_QOS_UNSPECIFIED, qos_override;
        thread_t thread = kqr->kqr_thread;
        int rc = 0, op = KQWL_UTQ_NONE;

        kqlock_held(kq);

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_BEGIN) | DBG_FUNC_START,
                      kqwl->kqwl_dynamicid, 0, 0);

        /* nobody else should still be processing */
        assert((kq->kq_state & KQ_PROCESSING) == 0);

        kq->kq_state |= KQ_PROCESSING;

        if (!TAILQ_EMPTY(&kqr->kqr_suppressed)) {
                op = KQWL_UTQ_RESET_WAKEUP_OVERRIDE;
        }

        if (kevent_flags & KEVENT_FLAG_PARKING) {
                /*
                 * When "parking" we want to process events and if no events are found
                 * unbind.
                 *
                 * However, non overcommit threads sometimes park even when they have
                 * more work so that the pool can narrow.  For these, we need to unbind
                 * early, so that calling kqworkloop_update_threads_qos() can ask the
                 * workqueue subsystem whether the thread should park despite having
                 * pending events.
                 */
                if (kqr->kqr_state & KQR_THOVERCOMMIT) {
                        op = KQWL_UTQ_PARKING;
                } else {
                        op = KQWL_UTQ_UNBINDING;
                }
        }
        if (op == KQWL_UTQ_NONE) {
                goto done;
        }

        qos_override = kqworkloop_acknowledge_events(kqwl);

        kq_req_lock(kqwl);

        if (op == KQWL_UTQ_UNBINDING) {
                old_override = kqworkloop_unbind_locked(kqwl, thread);
                (void)kqueue_release(kqwl, KQUEUE_CANT_BE_LAST_REF);
        }
        kqworkloop_update_threads_qos(kqwl, op, qos_override);
        if (op == KQWL_UTQ_PARKING) {
                if (!TAILQ_EMPTY(&kqwl->kqwl_queue[KQWL_BUCKET_STAYACTIVE])) {
                        /*
                         * We cannot trust KQR_WAKEUP when looking at stay active knotes.
                         * We need to process once, and kqworkloop_end_processing will
                         * handle the unbind.
                         */
                } else if ((kqr->kqr_state & KQR_WAKEUP) == 0 || kqwl->kqwl_owner) {
                        old_override = kqworkloop_unbind_locked(kqwl, thread);
                        (void)kqueue_release(kqwl, KQUEUE_CANT_BE_LAST_REF);
                        rc = -1;
                }
        } else if (op == KQWL_UTQ_UNBINDING) {
                if (kqr->kqr_thread == thread) {
                        /*
                         * The thread request fired again, passed the admission check and
                         * got bound to the current thread again.
                         */
                } else {
                        rc = -1;
                }
        }

        if (rc == 0) {
                /*
                 * Reset wakeup bit to notice stay active events firing while we are
                 * processing, as we cannot rely on the stayactive bucket emptiness.
                 */
                kqr->kqr_wakeup_indexes &= ~KQWL_STAYACTIVE_FIRED_BIT;
        } else {
                kq->kq_state &= ~KQ_PROCESSING;
        }

        kq_req_unlock(kqwl);

        if (old_override) {
                thread_drop_ipc_override(thread);
        }

done:
        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_BEGIN) | DBG_FUNC_END,
                      kqwl->kqwl_dynamicid, 0, 0);

        return rc;
}

/*
 * 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
kqfile_begin_processing(struct kqueue *kq)
{
        struct kqtailq *suppressq;

        kqlock_held(kq);

        assert((kq->kq_state & (KQ_WORKQ | KQ_WORKLOOP)) == 0);
        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_BEGIN) | DBG_FUNC_START,
                      VM_KERNEL_UNSLIDE_OR_PERM(kq), 0);

        /* 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, NULL);
                waitq_assert_wait64((struct waitq *)&kq->kq_wqs,
                                CAST_EVENT64_T(suppressq), THREAD_UNINT | THREAD_WAIT_NOREPORT,
                                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_KQFILE)) {
                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;
}

/*
 * Try to end the processing, only called when a workq thread is attempting to
 * park (KEVENT_FLAG_PARKING is set).
 *
 * When returning -1, the kqworkq is setup again so that it is ready to be
 * processed.
 */
static int
kqworkq_end_processing(struct kqworkq *kqwq, struct kqrequest *kqr,
                int kevent_flags)
{
        if (!kqueue_queue_empty(&kqwq->kqwq_kqueue, kqr->kqr_qos_index)) {
                /* remember we didn't process everything */
                kq_req_lock(kqwq);
                kqr->kqr_state |= KQR_WAKEUP;
                kq_req_unlock(kqwq);
        }

        if (kevent_flags & KEVENT_FLAG_PARKING) {
                /*
                 * if acknowledge events "succeeds" it means there are events,
                 * which is a failure condition for end_processing.
                 */
                int rc = kqworkq_acknowledge_events(kqwq, kqr, kevent_flags,
                                KQWQAE_END_PROCESSING);
                if (rc == 0) {
                        return -1;
                }
        }

        return 0;
}

/*
 * Try to end the processing, only called when a workq thread is attempting to
 * park (KEVENT_FLAG_PARKING is set).
 *
 * When returning -1, the kqworkq is setup again so that it is ready to be
 * processed (as if kqworkloop_begin_processing had just been called).
 *
 * If successful and KEVENT_FLAG_PARKING was set in the kevent_flags,
 * the kqworkloop is unbound from its servicer as a side effect.
 */
static int
kqworkloop_end_processing(struct kqworkloop *kqwl, int flags, int kevent_flags)
{
        struct kqueue *kq = &kqwl->kqwl_kqueue;
        struct kqrequest *kqr = &kqwl->kqwl_request;
        thread_qos_t old_override = THREAD_QOS_UNSPECIFIED, qos_override;
        thread_t thread = kqr->kqr_thread;
        int rc = 0;

        kqlock_held(kq);

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_END) | DBG_FUNC_START,
                        kqwl->kqwl_dynamicid, 0, 0);

        if (flags & KQ_PROCESSING) {
                assert(kq->kq_state & KQ_PROCESSING);

                /*
                 * If we still have queued stayactive knotes, remember we didn't finish
                 * processing all of them.  This should be extremely rare and would
                 * require to have a lot of them registered and fired.
                 */
                if (!TAILQ_EMPTY(&kqwl->kqwl_queue[KQWL_BUCKET_STAYACTIVE])) {
                        kq_req_lock(kqwl);
                        kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_WAKEUP_QOS,
                                        KQWL_BUCKET_STAYACTIVE);
                        kq_req_unlock(kqwl);
                }

                /*
                 * When KEVENT_FLAG_PARKING is set, we need to attempt an unbind while
                 * still under the lock.
                 *
                 * So we do everything kqworkloop_unbind() would do, but because we're
                 * inside kqueue_process(), if the workloop actually received events
                 * while our locks were dropped, we have the opportunity to fail the end
                 * processing and loop again.
                 *
                 * This avoids going through the process-wide workqueue lock hence
                 * scales better.
                 */
                if (kevent_flags & KEVENT_FLAG_PARKING) {
                        qos_override = kqworkloop_acknowledge_events(kqwl);
                }
        }

        kq_req_lock(kqwl);

        if (kevent_flags & KEVENT_FLAG_PARKING) {
                kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_PARKING, qos_override);
                if ((kqr->kqr_state & KQR_WAKEUP) && !kqwl->kqwl_owner) {
                        /*
                         * Reset wakeup bit to notice stay active events firing while we are
                         * processing, as we cannot rely on the stayactive bucket emptiness.
                         */
                        kqr->kqr_wakeup_indexes &= ~KQWL_STAYACTIVE_FIRED_BIT;
                        rc = -1;
                } else {
                        old_override = kqworkloop_unbind_locked(kqwl, thread);
                        (void)kqueue_release(kqwl, KQUEUE_CANT_BE_LAST_REF);
                        kq->kq_state &= ~flags;
                }
        } else {
                kq->kq_state &= ~flags;
                kqr->kqr_state |= KQR_R2K_NOTIF_ARMED;
                kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_RECOMPUTE_WAKEUP_QOS, 0);
        }

        kq_req_unlock(kqwl);

        if (old_override) {
                thread_drop_ipc_override(thread);
        }

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_PROCESS_END) | DBG_FUNC_END,
                        kqwl->kqwl_dynamicid, 0, 0);

        return rc;
}

/*
 * Called with kqueue lock held.
 */
static void
kqfile_end_processing(struct kqueue *kq)
{
        struct knote *kn;
        struct kqtailq *suppressq;
        int procwait;

        kqlock_held(kq);

        assert((kq->kq_state & (KQ_WORKQ|KQ_WORKLOOP)) == 0);

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQ_PROCESS_END),
                        VM_KERNEL_UNSLIDE_OR_PERM(kq), 0);

        /*
         * Return suppressed knotes to their original state.
         */
        suppressq = kqueue_get_suppressed_queue(kq, NULL);
        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);
        }
}

static int
kqueue_workloop_ctl_internal(proc_t p, uintptr_t cmd, uint64_t __unused options,
                struct kqueue_workloop_params *params, int *retval)
{
        int error = 0;
        int fd;
        struct fileproc *fp;
        struct kqueue *kq;
        struct kqworkloop *kqwl;
        struct filedesc *fdp = p->p_fd;
        workq_threadreq_param_t trp = { };

        switch (cmd) {
        case KQ_WORKLOOP_CREATE:
                if (!params->kqwlp_flags) {
                        error = EINVAL;
                        break;
                }

                if ((params->kqwlp_flags & KQ_WORKLOOP_CREATE_SCHED_PRI) &&
                                (params->kqwlp_sched_pri < 1 ||
                                 params->kqwlp_sched_pri > 63 /* MAXPRI_USER */)) {
                        error = EINVAL;
                        break;
                }

                if ((params->kqwlp_flags & KQ_WORKLOOP_CREATE_SCHED_POL) &&
                                invalid_policy(params->kqwlp_sched_pol)) {
                        error = EINVAL;
                        break;
                }

                if ((params->kqwlp_flags & KQ_WORKLOOP_CREATE_CPU_PERCENT) &&
                                (params->kqwlp_cpu_percent <= 0 ||
                                 params->kqwlp_cpu_percent > 100 ||
                                 params->kqwlp_cpu_refillms <= 0 ||
                                 params->kqwlp_cpu_refillms > 0x00ffffff)) {
                        error = EINVAL;
                        break;
                }

                if (params->kqwlp_flags & KQ_WORKLOOP_CREATE_SCHED_PRI) {
                        trp.trp_flags |= TRP_PRIORITY;
                        trp.trp_pri = params->kqwlp_sched_pri;
                }
                if (params->kqwlp_flags & KQ_WORKLOOP_CREATE_SCHED_POL) {
                        trp.trp_flags |= TRP_POLICY;
                        trp.trp_pol = params->kqwlp_sched_pol;
                }
                if (params->kqwlp_flags & KQ_WORKLOOP_CREATE_CPU_PERCENT) {
                        trp.trp_flags |= TRP_CPUPERCENT;
                        trp.trp_cpupercent = (uint8_t)params->kqwlp_cpu_percent;
                        trp.trp_refillms = params->kqwlp_cpu_refillms;
                }

                error = kevent_get_kq(p, params->kqwlp_id, &trp,
                                KEVENT_FLAG_DYNAMIC_KQUEUE | KEVENT_FLAG_WORKLOOP |
                                KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST , &fp, &fd, &kq);
                if (error) {
                        break;
                }

                if (!(fdp->fd_flags & FD_WORKLOOP)) {
                        /* FD_WORKLOOP indicates we've ever created a workloop
                         * via this syscall but its only ever added to a process, never
                         * removed.
                         */
                        proc_fdlock(p);
                        fdp->fd_flags |= FD_WORKLOOP;
                        proc_fdunlock(p);
                }
                break;
        case KQ_WORKLOOP_DESTROY:
                error = kevent_get_kq(p, params->kqwlp_id, NULL,
                                KEVENT_FLAG_DYNAMIC_KQUEUE | KEVENT_FLAG_WORKLOOP |
                                KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST , &fp, &fd, &kq);
                if (error) {
                        break;
                }
                kqlock(kq);
                kqwl = (struct kqworkloop *)kq;
                trp.trp_value = kqwl->kqwl_params;
                if (trp.trp_flags && !(trp.trp_flags & TRP_RELEASED)) {
                        trp.trp_flags |= TRP_RELEASED;
                        kqueue_release(kq, KQUEUE_CANT_BE_LAST_REF);
                } else {
                        error = EINVAL;
                }
                kqunlock(kq);
                kqueue_release_last(p, kq);
                break;
        }
        *retval = 0;
        return error;
}

int
kqueue_workloop_ctl(proc_t p, struct kqueue_workloop_ctl_args *uap, int *retval)
{
        struct kqueue_workloop_params params = {
                .kqwlp_id = 0,
        };
        if (uap->sz < sizeof(params.kqwlp_version)) {
                return EINVAL;
        }

        size_t copyin_sz = MIN(sizeof(params), uap->sz);
        int rv = copyin(uap->addr, &params, copyin_sz);
        if (rv) {
                return rv;
        }

        if (params.kqwlp_version != (int)uap->sz) {
                return EINVAL;
        }

        return kqueue_workloop_ctl_internal(p, uap->cmd, uap->options, &params,
                        retval);
}

/*
 * 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).
 *
 *      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 uthread *ut = get_bsdthread_info(current_thread());
        struct kqrequest *kqr = ut->uu_kqr_bound;
        struct knote *kn;
        unsigned int flags = process_data ? process_data->fp_flags : 0;
        int nevents = 0, error = 0, rc = 0;
        struct kqtailq *base_queue, *queue;
        kqueue_t kqu = { .kq = kq };
#if DEBUG || DEVELOPMENT
        int retries = 64;
#endif

        if (kq->kq_state & KQ_WORKQ) {
                if (kqr == NULL || (kqr->kqr_state & KQR_WORKLOOP)) {
                        return EJUSTRETURN;
                }
                rc = kqworkq_begin_processing(kqu.kqwq, kqr, flags);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                if (ut->uu_kqr_bound != &kqu.kqwl->kqwl_request) {
                        return EJUSTRETURN;
                }
                rc = kqworkloop_begin_processing(kqu.kqwl, flags);
        } else {
                rc = kqfile_begin_processing(kq);
        }

        if (rc == -1) {
                /* Nothing to process */
                *countp = 0;
                return 0;
        }

        /*
         * 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.
         */

process_again:
        if (kq->kq_state & KQ_WORKQ) {
                base_queue = queue = &kqu.kqwq->kqwq_queue[kqr->kqr_qos_index];
        } else if (kq->kq_state & KQ_WORKLOOP) {
                base_queue = &kqu.kqwl->kqwl_queue[0];
                queue = &kqu.kqwl->kqwl_queue[KQWL_NBUCKETS - 1];
        } else {
                base_queue = queue = &kq->kq_queue[QOS_INDEX_KQFILE];
        }

        do {
                while (error == 0 && (kn = TAILQ_FIRST(queue)) != NULL) {
                        error = knote_process(kn, callback, callback_data, process_data);
                        if (error == EJUSTRETURN) {
                                error = 0;
                        } else {
                                nevents++;
                        }
                        /* error is EWOULDBLOCK when the out event array is full */
                }

                if (error == EWOULDBLOCK) {
                        /* break out if no more space for additional events */
                        error = 0;
                        break;
                }
        } while (queue-- > base_queue);

        *countp = nevents;

        /*
         * If KEVENT_FLAG_PARKING is set, and no kevents have been returned,
         * we want to unbind the kqrequest from the thread.
         *
         * However, because the kq locks are dropped several times during process,
         * new knotes may have fired again, in which case, we want to fail the end
         * processing and process again, until it converges.
         *
         * If we returned events however, end processing never fails.
         */
        if (error || nevents) flags &= ~KEVENT_FLAG_PARKING;
        if (kq->kq_state & KQ_WORKQ) {
                rc = kqworkq_end_processing(kqu.kqwq, kqr, flags);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                rc = kqworkloop_end_processing(kqu.kqwl, KQ_PROCESSING, flags);
        } else {
                kqfile_end_processing(kq);
                rc = 0;
        }
        if (rc == -1) {
                assert(flags & KEVENT_FLAG_PARKING);
#if DEBUG || DEVELOPMENT
                if (retries-- == 0) {
                        panic("kevent: way too many knote_process retries, kq: %p (0x%02x)",
                                        kq, kq->kq_state);
                }
#endif
                goto process_again;
        }
        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_save.uus_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);
                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,
            __unused 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);
                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_save.uus_kqueue_scan;

                                cont_args->call = callback;
                                cont_args->cont = continuation;
                                cont_args->deadline = deadline;
                                cont_args->data = callback_data;
                                cont_args->process_data = process_data;
                                cont = kqueue_scan_continue;
                        }
                }

                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 (kqfile_begin_processing(kq) == -1) {
                kqunlock(kq);
                return (0);
        }

        queue = &kq->kq_queue[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, NULL);
                while ((kn = (struct knote *)TAILQ_FIRST(suppressq)) != NULL) {
                        KNOTE_LOCK_CTX(knlc);
                        int result = 0;

                        /* If didn't vanish while suppressed - peek at it */
                        if ((kn->kn_status & KN_DROPPING) || !knote_lock(kq, kn, &knlc,
                                        KNOTE_KQ_LOCK_ON_FAILURE)) {
                                continue;
                        }

                        result = filter_call(knote_fops(kn), f_peek(kn));

                        kqlock(kq);
                        knote_unlock(kq, kn, &knlc, KNOTE_KQ_LOCK_ALWAYS);

                        /* unsuppress it */
                        knote_unsuppress(kn);

                        /* has data or it has to report a vanish */
                        if (result & FILTER_ACTIVE) {
                                retnum = 1;
                                goto out;
                        }
                }
        }

out:
        kqfile_end_processing(kq);
        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);
}

/*
 * Max depth of the nested kq path that can be created.
 * Note that this has to be less than the size of kq_level
 * to avoid wrapping around and mislabeling the level.
 */
#define MAX_NESTED_KQ 1000

/*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);
        uint16_t plevel = 0;

        assert((kqf->kqf_state & KQ_WORKQ) == 0);

        if (parentkq == kq || kn->kn_filter != EVFILT_READ) {
                knote_set_error(kn, 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.
         *
         * Only up to MAX_NESTED_KQ can be nested.
         */

        kqlock(parentkq);
        if (parentkq->kq_level > 0 &&
            parentkq->kq_level < kq->kq_level)
        {
                kqunlock(parentkq);
                knote_set_error(kn, EINVAL);
                return 0;
        } else {
                /* set parent level appropriately */
                plevel = (parentkq->kq_level == 0)? 2: parentkq->kq_level;
                if (plevel < kq->kq_level + 1) {
                        if (kq->kq_level + 1 > MAX_NESTED_KQ) {
                                kqunlock(parentkq);
                                knote_set_error(kn, EINVAL);
                                return 0;
                        }
                        plevel = kq->kq_level + 1;
                }

                parentkq->kq_level = plevel;
                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 at a specific QoS
 * level.
 *
 * - 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
kqueue_threadreq_initiate(struct kqueue *kq, struct kqrequest *kqr,
                kq_index_t qos, int flags)
{
        assert(kqr->kqr_state & KQR_WAKEUP);
        assert(kqr->kqr_thread == THREAD_NULL);
        assert((kqr->kqr_state & KQR_THREQUESTED) == 0);
        struct turnstile *ts = TURNSTILE_NULL;

        if (workq_is_exiting(kq->kq_p)) {
                return;
        }

        /* Add a thread request reference on the kqueue. */
        kqueue_retain(kq);

        kq_req_held(kq);

        if (kq->kq_state & KQ_WORKLOOP) {
                __assert_only struct kqworkloop *kqwl = (struct kqworkloop *)kq;

                assert(kqwl->kqwl_owner == THREAD_NULL);
                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_THREQUEST),
                                kqwl->kqwl_dynamicid, 0, qos, kqr->kqr_state);
                ts = kqwl->kqwl_turnstile;
        } else {
                assert(kq->kq_state & KQ_WORKQ);
                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_THREQUEST),
                                -1, 0, qos, kqr->kqr_state);
        }

        kqr->kqr_state |= 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 kqueue_threadreq_bind callback.
         */
#if 0 // 45129862
        if ((kq->kq_state & KQ_WORKLOOP) && current_proc() == kq->kq_p) {
                flags |= WORKQ_THREADREQ_SET_AST_ON_FAILURE;
        }
#endif
        if (qos == KQWQ_QOS_MANAGER) {
                qos = WORKQ_THREAD_QOS_MANAGER;
        }
        if (!workq_kern_threadreq_initiate(kq->kq_p, kqr, ts, qos, flags)) {
                /*
                 * 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.
                 */
                kqr->kqr_state &= ~(KQR_THREQUESTED | KQR_R2K_NOTIF_ARMED);
                kqueue_release(kq, KQUEUE_CANT_BE_LAST_REF);
        }
}

/*
 * kqueue_threadreq_bind_prepost - prepost the bind to kevent
 *
 * This is used when kqueue_threadreq_bind may cause a lock inversion.
 */
void
kqueue_threadreq_bind_prepost(struct proc *p __unused, workq_threadreq_t req,
                thread_t thread)
{
        struct kqrequest *kqr = __container_of(req, struct kqrequest, kqr_req);
        struct uthread *ut = get_bsdthread_info(thread);

        req->tr_binding_thread = thread;
        ut->uu_kqr_bound = kqr;
        req->tr_state = TR_STATE_BINDING;

        struct kqworkloop *kqwl = kqr_kqworkloop(kqr);
        if (kqwl && kqwl->kqwl_turnstile) {
                struct turnstile *ts = kqwl->kqwl_turnstile;
                /*
                 * While a thread request is in flight, the workqueue
                 * is the interlock for the turnstile and can update the inheritor.
                 */
                turnstile_update_inheritor(ts, thread, TURNSTILE_IMMEDIATE_UPDATE |
                                TURNSTILE_INHERITOR_THREAD);
                turnstile_update_inheritor_complete(ts, TURNSTILE_INTERLOCK_HELD);
        }
}

/*
 * kqueue_threadreq_bind_commit - commit a bind prepost
 *
 * The workq code has to commit any binding prepost before the thread has
 * a chance to come back to userspace (and do kevent syscalls) or be aborted.
 */
void
kqueue_threadreq_bind_commit(struct proc *p, thread_t thread)
{
        struct uthread *ut = get_bsdthread_info(thread);
        struct kqrequest *kqr = ut->uu_kqr_bound;
        kqueue_t kqu = kqr_kqueue(p, kqr);

        kq_req_lock(kqu);
        if (kqr->kqr_req.tr_state == TR_STATE_BINDING) {
                kqueue_threadreq_bind(p, &kqr->kqr_req, thread, 0);
        }
        kq_req_unlock(kqu);
}

static void
kqueue_threadreq_modify(struct kqueue *kq, struct kqrequest *kqr, kq_index_t qos)
{
        assert(kqr->kqr_state & KQR_THREQUESTED);
        assert(kqr->kqr_thread == THREAD_NULL);

        kq_req_held(kq);

        int flags = 0;
#if 0 // 45129862
        if ((kq->kq_state & KQ_WORKLOOP) && kq->kq_p == current_proc()) {
                flags |= WORKQ_THREADREQ_SET_AST_ON_FAILURE;
        }
#endif
        workq_kern_threadreq_modify(kq->kq_p, kqr, qos, flags);
}

/*
 * kqueue_threadreq_bind - bind thread to processing kqrequest
 *
 * 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.
 */
void
kqueue_threadreq_bind(struct proc *p, workq_threadreq_t req, thread_t thread,
                unsigned int flags)
{
        struct kqrequest *kqr = __container_of(req, struct kqrequest, kqr_req);
        kqueue_t kqu = kqr_kqueue(p, kqr);
        struct uthread *ut = get_bsdthread_info(thread);

        kq_req_held(kqu);

        assert(kqr->kqr_state & KQR_THREQUESTED);
        assert(kqr->kqr_thread == THREAD_NULL);
        assert(ut->uu_kqueue_override == 0);

        if (kqr->kqr_req.tr_state == TR_STATE_BINDING) {
                assert(ut->uu_kqr_bound == kqr);
                assert(kqr->kqr_req.tr_binding_thread == thread);
                kqr->kqr_req.tr_state = TR_STATE_IDLE;
                kqr->kqr_req.tr_binding_thread = NULL;
        } else {
                assert(ut->uu_kqr_bound == NULL);
        }

        ut->uu_kqr_bound = kqr;
        kqr->kqr_thread = thread;

        if (kqu.kq->kq_state & KQ_WORKLOOP) {
                struct turnstile *ts = kqu.kqwl->kqwl_turnstile;

                if (__improbable(thread == kqu.kqwl->kqwl_owner)) {
                        /*
                         * <rdar://problem/38626999> shows that asserting here is not ok.
                         *
                         * This is not supposed to happen for correct use of the interface,
                         * but it is sadly possible for userspace (with the help of memory
                         * corruption, such as over-release of a dispatch queue) to make
                         * the creator thread the "owner" of a workloop.
                         *
                         * Once that happens, and that creator thread picks up the same
                         * workloop as a servicer, we trip this codepath. We need to fixup
                         * the state to forget about this thread being the owner, as the
                         * entire workloop state machine expects servicers to never be
                         * owners and everything would basically go downhill from here.
                         */
                        kqu.kqwl->kqwl_owner = THREAD_NULL;
                        if (kqworkloop_owner_override(kqu.kqwl)) {
                                thread_drop_ipc_override(thread);
                        }
                        thread_ends_owning_workloop(thread);
                }

                if (ts && (flags & KQUEUE_THREADERQ_BIND_NO_INHERITOR_UPDATE) == 0) {
                        /*
                         * Past this point, the interlock is the kq req lock again,
                         * so we can fix the inheritor for good.
                         */
                        filt_wlupdate_inheritor(kqu.kqwl, ts, TURNSTILE_IMMEDIATE_UPDATE);
                        turnstile_update_inheritor_complete(ts, TURNSTILE_INTERLOCK_HELD);
                }

                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_BIND), kqu.kqwl->kqwl_dynamicid,
                                thread_tid(thread), kqr->kqr_qos_index,
                                (kqr->kqr_override_index << 16) | kqr->kqr_state);

                ut->uu_kqueue_override = kqr->kqr_override_index;
                if (kqr->kqr_override_index) {
                        thread_add_ipc_override(thread, kqr->kqr_override_index);
                }
        } else {
                assert(kqr->kqr_override_index == 0);

                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_BIND), -1,
                                thread_tid(thread), kqr->kqr_qos_index,
                                (kqr->kqr_override_index << 16) | kqr->kqr_state);
        }
}

/*
 * kqueue_threadreq_cancel - abort a pending thread request
 *
 * Called when exiting/exec'ing. Forget our pending request.
 */
void
kqueue_threadreq_cancel(struct proc *p, workq_threadreq_t req)
{
        struct kqrequest *kqr = __container_of(req, struct kqrequest, kqr_req);
        kqueue_t kqu = kqr_kqueue(p, kqr);

        kq_req_lock(kqu);

        assert(kqr->kqr_thread == THREAD_NULL);
        assert(kqr->kqr_state & KQR_THREQUESTED);
        kqr->kqr_state &= ~(KQR_THREQUESTED | KQR_R2K_NOTIF_ARMED);

        kq_req_unlock(kqu);

        kqueue_release_last(p, kqu); /* may dealloc kqu */
}

workq_threadreq_param_t
kqueue_threadreq_workloop_param(workq_threadreq_t req)
{
        struct kqrequest *kqr = __container_of(req, struct kqrequest, kqr_req);
        struct kqworkloop *kqwl;
        workq_threadreq_param_t trp;

        assert(kqr->kqr_state & KQR_WORKLOOP);
        kqwl = __container_of(kqr, struct kqworkloop, kqwl_request);
        trp.trp_value = kqwl->kqwl_params;
        return trp;
}

/*
 *      kqueue_threadreq_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.
 */
void
kqueue_threadreq_unbind(struct proc *p, struct kqrequest *kqr)
{
        if (kqr->kqr_state & KQR_WORKLOOP) {
                kqworkloop_unbind(p, kqr_kqworkloop(kqr));
        } else {
                kqworkq_unbind(p, kqr);
        }
}

/*
 * 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_NBUCKETS);

        kq_req_lock(kqwq);
        kqr = kqworkq_get_request(kqwq, qos_index);

        if ((kqr->kqr_state & KQR_WAKEUP) == 0) {
                kqr->kqr_state |= KQR_WAKEUP;
                if ((kqr->kqr_state & KQR_THREQUESTED) == 0) {
                        kqueue_threadreq_initiate(&kqwq->kqwq_kqueue, kqr, qos_index, 0);
                }
        }
        kq_req_unlock(kqwq);
}

static kq_index_t
kqworkloop_owner_override(struct kqworkloop *kqwl)
{
        struct kqrequest *kqr = &kqwl->kqwl_request;
        return MAX(kqr->kqr_qos_index, kqr->kqr_override_index);
}

static inline void
kqworkloop_request_fire_r2k_notification(struct kqworkloop *kqwl)
{
        struct kqrequest *kqr = &kqwl->kqwl_request;

        kq_req_held(kqwl);

        if (kqr->kqr_state & KQR_R2K_NOTIF_ARMED) {
                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)
{
        struct kqrequest *kqr = &kqwl->kqwl_request;
        struct kqueue *kq = &kqwl->kqwl_kqueue;
        kq_index_t old_owner_override = kqworkloop_owner_override(kqwl);
        kq_index_t i;

        /* must hold the kqr lock */
        kq_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);
                }
                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;

        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;
                        }
                }
                break;

        case KQWL_UTQ_PARKING:
        case KQWL_UTQ_UNBINDING:
                kqr->kqr_override_index = qos;
                /* FALLTHROUGH */
        case KQWL_UTQ_RECOMPUTE_WAKEUP_QOS:
                if (op == KQWL_UTQ_RECOMPUTE_WAKEUP_QOS) {
                        assert(qos == THREAD_QOS_UNSPECIFIED);
                }
                kqlock_held(kqwl); // to look at kq_queues
                i = KQWL_BUCKET_STAYACTIVE;
                if (TAILQ_EMPTY(&kqr->kqr_suppressed)) {
                        kqr->kqr_override_index = THREAD_QOS_UNSPECIFIED;
                }
                if (!TAILQ_EMPTY(&kqwl->kqwl_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(&kqwl->kqwl_queue[i])) {
                                kqr->kqr_wakeup_indexes |= (1 << i);
                        }
                }
                if (kqr->kqr_wakeup_indexes) {
                        kqr->kqr_state |= KQR_WAKEUP;
                        kqworkloop_request_fire_r2k_notification(kqwl);
                } else {
                        kqr->kqr_state &= ~KQR_WAKEUP;
                }
                goto recompute;

        case KQWL_UTQ_RESET_WAKEUP_OVERRIDE:
                kqr->kqr_override_index = qos;
                goto recompute;

        case KQWL_UTQ_UPDATE_WAKEUP_OVERRIDE:
        recompute:
                /*
                 * When modifying the wakeup QoS or the 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_QOS_INDEX:
                kqr->kqr_qos_index = qos;
                break;

        default:
                panic("unknown kqwl thread qos update operation: %d", op);
        }

        thread_t kqwl_owner = kqwl->kqwl_owner;
        thread_t servicer = kqr->kqr_thread;
        boolean_t qos_changed = FALSE;
        kq_index_t new_owner_override = kqworkloop_owner_override(kqwl);

        /*
         * Apply the diffs to the owner if applicable
         */
        if (kqwl_owner) {
#if 0
                /* JMM - need new trace hooks for owner overrides */
                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_THADJUST),
                                kqwl->kqwl_dynamicid, thread_tid(kqwl_owner), kqr->kqr_qos_index,
                                (kqr->kqr_override_index << 16) | kqr->kqr_state);
#endif
                if (new_owner_override == old_owner_override) {
                        // nothing to do
                } else if (old_owner_override == THREAD_QOS_UNSPECIFIED) {
                        thread_add_ipc_override(kqwl_owner, new_owner_override);
                } else if (new_owner_override == THREAD_QOS_UNSPECIFIED) {
                        thread_drop_ipc_override(kqwl_owner);
                } else /*  old_owner_override != new_owner_override */ {
                        thread_update_ipc_override(kqwl_owner, new_owner_override);
                }
        }

        /*
         * apply the diffs to the servicer
         */
        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 == NULL && (kqr->kqr_state & KQR_WAKEUP)) {
                        int initiate_flags = 0;
                        if (op == KQWL_UTQ_UNBINDING) {
                                initiate_flags = WORKQ_THREADREQ_ATTEMPT_REBIND;
                        }
                        kqueue_threadreq_initiate(kq, kqr, new_owner_override,
                                        initiate_flags);
                }
        } else if (servicer) {
                /*
                 * Servicer in flight
                 *
                 * Just apply the diff to the servicer
                 */
                struct uthread *ut = get_bsdthread_info(servicer);
                if (ut->uu_kqueue_override != kqr->kqr_override_index) {
                        if (ut->uu_kqueue_override == THREAD_QOS_UNSPECIFIED) {
                                thread_add_ipc_override(servicer, kqr->kqr_override_index);
                        } else if (kqr->kqr_override_index == THREAD_QOS_UNSPECIFIED) {
                                thread_drop_ipc_override(servicer);
                        } else /* ut->uu_kqueue_override != kqr->kqr_override_index */ {
                                thread_update_ipc_override(servicer, kqr->kqr_override_index);
                        }
                        ut->uu_kqueue_override = kqr->kqr_override_index;
                        qos_changed = TRUE;
                }
        } else if (new_owner_override == THREAD_QOS_UNSPECIFIED) {
                /*
                 * No events to deliver anymore.
                 *
                 * However canceling with turnstiles is challenging, so the fact that
                 * the request isn't useful will be discovered by the servicer himself
                 * later on.
                 */
        } else if (old_owner_override != new_owner_override) {
                /*
                 * Request is in flight
                 *
                 * Apply the diff to the thread request
                 */
                kqueue_threadreq_modify(kq, kqr, new_owner_override);
                qos_changed = TRUE;
        }

        if (qos_changed) {
                KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_THADJUST), kqwl->kqwl_dynamicid,
                                thread_tid(kqr->kqr_thread), kqr->kqr_qos_index,
                                (kqr->kqr_override_index << 16) | 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);

        kq_req_lock(kqwl);
        kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_WAKEUP_QOS, qos_index);
        kq_req_unlock(kqwl);
}

static struct kqtailq *
kqueue_get_queue(struct kqueue *kq, kq_index_t qos_index)
{
        if (kq->kq_state & KQ_WORKQ) {
                assert(qos_index < KQWQ_NBUCKETS);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                assert(qos_index < KQWL_NBUCKETS);
        } else {
                assert(qos_index == QOS_INDEX_KQFILE);
        }
        static_assert(offsetof(struct kqueue, kq_queue) == sizeof(struct kqueue),
                        "struct kqueue::kq_queue must be exactly at the end");
        return &kq->kq_queue[qos_index];
}

static int
kqueue_queue_empty(struct kqueue *kq, kq_index_t qos_index)
{
        return TAILQ_EMPTY(kqueue_get_queue(kq, qos_index));
}

static struct kqtailq *
kqueue_get_suppressed_queue(kqueue_t kq, struct knote *kn)
{
        if (kq.kq->kq_state & KQ_WORKQ) {
                return &kqworkq_get_request(kq.kqwq, kn->kn_qos_index)->kqr_suppressed;
        } else if (kq.kq->kq_state & KQ_WORKLOOP) {
                return &kq.kqwl->kqwl_request.kqr_suppressed;
        } else {
                return &kq.kqf->kqf_suppressed;
        }
}

static struct turnstile *
kqueue_get_turnstile(kqueue_t kqu, bool can_alloc)
{
        uint8_t kqr_state;

        if ((kqu.kq->kq_state & KQ_WORKLOOP) == 0) {
                return TURNSTILE_NULL;
        }

        kqr_state = os_atomic_load(&kqu.kqwl->kqwl_request.kqr_state, relaxed);
        if (kqr_state & KQR_ALLOCATED_TURNSTILE) {
                /* force a dependency to pair with the atomic or with release below */
                return os_atomic_load_with_dependency_on(&kqu.kqwl->kqwl_turnstile,
                                kqr_state);
        }

        if (!can_alloc) {
                return TURNSTILE_NULL;
        }

        struct turnstile *ts = turnstile_alloc(), *free_ts = TURNSTILE_NULL;

        kq_req_lock(kqu);
        if (filt_wlturnstile_interlock_is_workq(kqu.kqwl)) {
                workq_kern_threadreq_lock(kqu.kqwl->kqwl_p);
        }

        if (kqu.kqwl->kqwl_request.kqr_state & KQR_ALLOCATED_TURNSTILE) {
                free_ts = ts;
                ts = kqu.kqwl->kqwl_turnstile;
        } else {
                ts = turnstile_prepare((uintptr_t)kqu.kqwl, &kqu.kqwl->kqwl_turnstile,
                                ts, TURNSTILE_WORKLOOPS);

                /* release-barrier to pair with the unlocked load of kqwl_turnstile above */
                os_atomic_or(&kqu.kqwl->kqwl_request.kqr_state,
                                KQR_ALLOCATED_TURNSTILE, release);
        }

        if (filt_wlturnstile_interlock_is_workq(kqu.kqwl)) {
                workq_kern_threadreq_unlock(kqu.kqwl->kqwl_p);
        }
        kq_req_unlock(kqu.kqwl);

        if (free_ts) {
                turnstile_deallocate(free_ts);
        }
        return ts;
}

struct turnstile *
kqueue_turnstile(struct kqueue *kq)
{
        return kqueue_get_turnstile(kq, false);
}

struct turnstile *
kqueue_alloc_turnstile(struct kqueue *kq)
{
        return kqueue_get_turnstile(kq, true);
}

static struct kqtailq *
knote_get_queue(struct knote *kn)
{
        return kqueue_get_queue(knote_get_kq(kn), kn->kn_qos_index);
}

static void
knote_reset_priority(struct knote *kn, pthread_priority_t pp)
{
        struct kqueue *kq = knote_get_kq(kn);
        kq_index_t qos = _pthread_priority_thread_qos(pp);

        assert((kn->kn_status & KN_QUEUED) == 0);

        if (kq->kq_state & KQ_WORKQ) {
                if (qos == THREAD_QOS_UNSPECIFIED) {
                        /* On workqueues, outside of QoS means MANAGER */
                        qos = KQWQ_QOS_MANAGER;
                        pp = _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
                } else {
                        pp = _pthread_priority_normalize(pp);
                }
        } else if (kq->kq_state & KQ_WORKLOOP) {
                assert((pp & _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG) == 0);
                pp = _pthread_priority_normalize(pp);
        } else {
                pp = _pthread_unspecified_priority();
                qos = THREAD_QOS_UNSPECIFIED;
        }

        kn->kn_qos = pp;
        kn->kn_req_index = qos;

        if ((kn->kn_status & KN_MERGE_QOS) == 0 || qos > kn->kn_qos_override) {
                /* Never lower QoS when in "Merge" mode */
                kn->kn_qos_override = qos;
        }

        /* only adjust in-use qos index when not suppressed */
        if ((kn->kn_status & KN_SUPPRESSED) == 0) {
                kn->kn_qos_index = qos;
        } else if (kq->kq_state & KQ_WORKQ) {
                kqworkq_update_override((struct kqworkq *)kq, kn, qos);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                kqworkloop_update_override((struct kqworkloop *)kq, qos);
        }
}

static void
knote_set_qos_overcommit(struct knote *kn)
{
        struct kqueue *kq = knote_get_kq(kn);

        /* turn overcommit on for the appropriate thread request? */
        if ((kn->kn_qos & _PTHREAD_PRIORITY_OVERCOMMIT_FLAG) &&
                        (kq->kq_state & KQ_WORKLOOP)) {
                struct kqworkloop *kqwl = (struct kqworkloop *)kq;
                struct kqrequest *kqr = &kqwl->kqwl_request;

                /*
                 * This test is racy, but since we never remove this bit,
                 * it allows us to avoid taking a lock.
                 */
                if (kqr->kqr_state & KQR_THOVERCOMMIT) {
                        return;
                }

                kq_req_lock(kqwl);
                kqr->kqr_state |= KQR_THOVERCOMMIT;
                if (!kqr->kqr_thread && (kqr->kqr_state & KQR_THREQUESTED)) {
                        kqueue_threadreq_modify(kq, kqr, kqr->kqr_req.tr_qos);
                }
                kq_req_unlock(kqwl);
        }
}

static kq_index_t
knote_get_qos_override_index(struct knote *kn)
{
        return kn->kn_qos_override;
}

static void
kqworkq_update_override(struct kqworkq *kqwq, struct knote *kn,
                kq_index_t override_index)
{
        struct kqrequest *kqr;
        kq_index_t old_override_index;
        kq_index_t queue_index = kn->kn_qos_index;

        if (override_index <= queue_index) {
                return;
        }

        kqr = kqworkq_get_request(kqwq, queue_index);

        kq_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_thread) {
                        if (old_override_index)
                                thread_update_ipc_override(kqr->kqr_thread, override_index);
                        else
                                thread_add_ipc_override(kqr->kqr_thread, override_index);
                }
        }
        kq_req_unlock(kqwq);
}

static void
kqworkloop_update_override(struct kqworkloop *kqwl, kq_index_t override_index)
{
        kq_req_lock(kqwl);
        kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_WAKEUP_OVERRIDE,
                        override_index);
        kq_req_unlock(kqwl);
}

static thread_qos_t
kqworkloop_unbind_locked(struct kqworkloop *kqwl, thread_t thread)
{
        struct uthread *ut = get_bsdthread_info(thread);
        struct kqrequest *kqr = &kqwl->kqwl_request;
        kq_index_t ipc_override = ut->uu_kqueue_override;

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWL_UNBIND), kqwl->kqwl_dynamicid,
                        thread_tid(thread), 0, 0);

        kq_req_held(kqwl);
        assert(ut->uu_kqr_bound == kqr);
        ut->uu_kqr_bound = NULL;
        ut->uu_kqueue_override = THREAD_QOS_UNSPECIFIED;

        if (kqwl->kqwl_owner == NULL && kqwl->kqwl_turnstile) {
                turnstile_update_inheritor(kqwl->kqwl_turnstile,
                                TURNSTILE_INHERITOR_NULL, TURNSTILE_IMMEDIATE_UPDATE);
                turnstile_update_inheritor_complete(kqwl->kqwl_turnstile,
                                TURNSTILE_INTERLOCK_HELD);
        }

        kqr->kqr_thread = NULL;
        kqr->kqr_state &= ~(KQR_THREQUESTED | KQR_R2K_NOTIF_ARMED);
        return ipc_override;
}

/*
 *      kqworkloop_unbind - Unbind the servicer thread of a workloop kqueue
 *
 *      It will acknowledge events, and possibly request a new thread if:
 *      - there were active events left
 *      - we pended waitq hook callouts during processing
 *      - we pended wakeups while processing (or unsuppressing)
 *
 *      Called with kqueue lock held.
 */
static void
kqworkloop_unbind(proc_t p, struct kqworkloop *kqwl)
{
        struct kqueue *kq = &kqwl->kqwl_kqueue;
        struct kqrequest *kqr = &kqwl->kqwl_request;
        thread_t thread = kqr->kqr_thread;
        int op = KQWL_UTQ_PARKING;
        kq_index_t ipc_override, qos_override = THREAD_QOS_UNSPECIFIED;

        assert(thread == current_thread());

        kqlock(kqwl);

        /*
         * 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.
         */
        assert((kq->kq_state & KQ_PROCESSING) == 0);
        if (!TAILQ_EMPTY(&kqr->kqr_suppressed)) {
                kq->kq_state |= KQ_PROCESSING;
                qos_override = kqworkloop_acknowledge_events(kqwl);
                kq->kq_state &= ~KQ_PROCESSING;
        }

        kq_req_lock(kqwl);

        ipc_override = kqworkloop_unbind_locked(kqwl, thread);
        kqworkloop_update_threads_qos(kqwl, op, qos_override);

        kq_req_unlock(kqwl);

        kqunlock(kqwl);

        /*
         * Drop the override on the current thread last, after the call to
         * kqworkloop_update_threads_qos above.
         */
        if (ipc_override) {
                thread_drop_ipc_override(thread);
        }

        /* If last reference, dealloc the workloop kq */
        kqueue_release_last(p, kqwl);
}

static thread_qos_t
kqworkq_unbind_locked(__assert_only struct kqworkq *kqwq,
                struct kqrequest *kqr, thread_t thread)
{
        struct uthread *ut = get_bsdthread_info(thread);
        kq_index_t old_override = kqr->kqr_override_index;

        KDBG_FILTERED(KEV_EVTID(BSD_KEVENT_KQWQ_UNBIND), -1,
                        thread_tid(kqr->kqr_thread), kqr->kqr_qos_index, 0);

        kq_req_held(kqwq);
        assert(ut->uu_kqr_bound == kqr);
        ut->uu_kqr_bound = NULL;
        kqr->kqr_thread = NULL;
        kqr->kqr_state &= ~(KQR_THREQUESTED | KQR_R2K_NOTIF_ARMED);
        kqr->kqr_override_index = THREAD_QOS_UNSPECIFIED;

        return old_override;
}

/*
 *      kqworkq_unbind - unbind of a workq kqueue from a thread
 *
 *      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)
 */
static void
kqworkq_unbind(proc_t p, struct kqrequest *kqr)
{
        struct kqworkq *kqwq = (struct kqworkq *)p->p_fd->fd_wqkqueue;
        __assert_only int rc;

        kqlock(kqwq);
        rc = kqworkq_acknowledge_events(kqwq, kqr, 0, KQWQAE_UNBIND);
        assert(rc == -1);
        kqunlock(kqwq);
}

struct kqrequest *
kqworkq_get_request(struct kqworkq *kqwq, kq_index_t qos_index)
{
        assert(qos_index < KQWQ_NBUCKETS);
        return &kqwq->kqwq_request[qos_index];
}

static void
knote_apply_qos_override(struct knote *kn, kq_index_t qos_index)
{
        assert((kn->kn_status & KN_QUEUED) == 0);

        kn->kn_qos_override = qos_index;

        if (kn->kn_status & KN_SUPPRESSED) {
                struct kqueue *kq = knote_get_kq(kn);
                /*
                 * For suppressed events, the kn_qos_index field cannot be touched as it
                 * allows us to know on which supress queue the knote is for a kqworkq.
                 *
                 * Also, there's no natural push applied on the kqueues when this field
                 * changes anyway. We hence need to apply manual overrides in this case,
                 * which will be cleared when the events are later acknowledged.
                 */
                if (kq->kq_state & KQ_WORKQ) {
                        kqworkq_update_override((struct kqworkq *)kq, kn, qos_index);
                } else {
                        kqworkloop_update_override((struct kqworkloop *)kq, qos_index);
                }
        } else {
                kn->kn_qos_index = qos_index;
        }
}

static bool
knote_should_apply_qos_override(struct kqueue *kq, struct knote *kn, int result,
                thread_qos_t *qos_out)
{
        thread_qos_t qos_index = (result >> FILTER_ADJUST_EVENT_QOS_SHIFT) & 7;

        kqlock_held(kq);

        assert(result & FILTER_ADJUST_EVENT_QOS_BIT);
        assert(qos_index < THREAD_QOS_LAST);

        /*
         * Early exit for knotes that should not change QoS
         *
         * It is safe to test kn_req_index against MANAGER / STAYACTIVE because
         * knotes with such kn_req_index values never change for their entire
         * lifetime.
         */
        if (__improbable(!knote_fops(kn)->f_adjusts_qos)) {
                panic("filter %d cannot change QoS", kn->kn_filtid);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                if (kn->kn_req_index == KQWL_BUCKET_STAYACTIVE) {
                        return false;
                }
        } else if (kq->kq_state & KQ_WORKQ) {
                if (kn->kn_req_index == KQWQ_QOS_MANAGER) {
                        return false;
                }
        } else {
                return false;
        }

        /*
         * knotes with the FALLBACK flag will only use their registration QoS if the
         * incoming event has no QoS, else, the registration QoS acts as a floor.
         */
        if (kn->kn_qos & _PTHREAD_PRIORITY_FALLBACK_FLAG) {
                if (qos_index == THREAD_QOS_UNSPECIFIED)
                        qos_index = kn->kn_req_index;
        } else {
                if (qos_index < kn->kn_req_index)
                        qos_index = kn->kn_req_index;
        }
        if ((kn->kn_status & KN_MERGE_QOS) && (qos_index < kn->kn_qos_override)) {
                /* Never lower QoS when in "Merge" mode */
                return false;
        }

        if ((kn->kn_status & KN_LOCKED) && kn->kn_inuse) {
                /*
                 * When we're trying to update the QoS override and that both an
                 * f_event() and other f_* calls are running concurrently, any of these
                 * in flight calls may want to perform overrides that aren't properly
                 * serialized with each other.
                 *
                 * The first update that observes this racy situation enters a "Merge"
                 * mode which causes subsequent override requests to saturate the
                 * override instead of replacing its value.
                 *
                 * This mode is left when knote_unlock() or knote_call_filter_event()
                 * observe that no other f_* routine is in flight.
                 */
                kn->kn_status |= KN_MERGE_QOS;
        }

        if (kn->kn_qos_override == qos_index) {
                return false;
        }

        *qos_out = qos_index;
        return true;
}

static void
knote_adjust_qos(struct kqueue *kq, struct knote *kn, int result)
{
        thread_qos_t qos;
        if (knote_should_apply_qos_override(kq, kn, result, &qos)) {
                knote_dequeue(kn);
                knote_apply_qos_override(kn, qos);
                if (knote_enqueue(kn) && (kn->kn_status & KN_ACTIVE)) {
                        knote_wakeup(kn);
                }
        }
}

static void
knote_wakeup(struct knote *kn)
{
        struct kqueue *kq = knote_get_kq(kn);

        kqlock_held(kq);

        if (kq->kq_state & KQ_WORKQ) {
                struct kqworkq *kqwq = (struct kqworkq *)kq;

                kqworkq_request_help(kqwq, kn->kn_qos_index);
        } else if (kq->kq_state & KQ_WORKLOOP) {
                struct kqworkloop *kqwl = (struct kqworkloop *)kq;

                /*
                 * kqworkloop_end_processing() will perform the required QoS
                 * computations when it unsets the processing mode.
                 */
                if (!kqworkloop_is_processing_on_current_thread(kqwl)) {
                        kqworkloop_request_help(kqwl, kn->kn_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, NULL);
                (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.
 */
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);
                knote_call_filter_event(kq, kn, hint);
                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);

                kqlock(kq);
                if (kn->kn_status & KN_REQVANISH) {
                        /* If EV_VANISH supported - prepare to deliver one */
                        kn->kn_status |= KN_VANISHED;
                        knote_activate(kn);
                } else {
                        knote_call_filter_event(kq, kn, NOTE_REVOKE);
                }
                kqunlock(kq);
        }
}

/*
 * Force a lazy allocation of the waitqset link
 * of the kq_wqs associated with the kn
 * if it wasn't already allocated.
 *
 * This allows knote_link_waitq to never block
 * if reserved_link is not NULL.
 */
void
knote_link_waitqset_lazy_alloc(struct knote *kn)
{
        struct kqueue *kq = knote_get_kq(kn);
        waitq_set_lazy_init_link(&kq->kq_wqs);
}

/*
 * Check if a lazy allocation for the waitqset link
 * of the kq_wqs is needed.
 */
boolean_t
knote_link_waitqset_should_lazy_alloc(struct knote *kn)
{
        struct kqueue *kq = knote_get_kq(kn);
        return waitq_set_should_lazy_init_link(&kq->kq_wqs);
}

/*
 * 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 and insures that the kq->kq_wqs
 * is linked by previously calling knote_link_waitqset_lazy_alloc.
 */
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
 *
 * 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)
{
        struct klist *list;
        struct knote *kn;
        KNOTE_LOCK_CTX(knlc);

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 (kn->kn_status & KN_VANISHED) {
                        kqunlock(kq);
                        continue;
                }

                proc_fdunlock(p);
                if (!knote_lock(kq, kn, &knlc, KNOTE_KQ_LOCK_ON_SUCCESS)) {
                        /* the knote was dropped by someone, nothing to do */
                } else if (kn->kn_status & KN_REQVANISH) {
                        kn->kn_status |= KN_VANISHED;
                        kn->kn_status &= ~KN_ATTACHED;

                        kqunlock(kq);
                        knote_fops(kn)->f_detach(kn);
                        if (knote_fops(kn)->f_isfd)
                                fp_drop(p, kn->kn_id, kn->kn_fp, 0);
                        kqlock(kq);

                        knote_activate(kn);
                        knote_unlock(kq, kn, &knlc, KNOTE_KQ_UNLOCK);
                } else {
                        knote_drop(kq, kn, &knlc);
                }

                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 knote_lock_ctx *knlc,
                struct proc *p)
{
        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, &kn->kn_kevent, 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) {
                kqlock(kq);
                assert((kn->kn_status & KN_LOCKED) == 0);
                (void)knote_lock(kq, kn, knlc, KNOTE_KQ_UNLOCK);
        }
        if (is_fd)
                proc_fdunlock(p);
        else
                knhash_unlock(p);

        return ret;
}

/*
 * kq_remove_knote - remove a knote from the fd table for process
 *
 * 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,
                struct knote_lock_ctx *knlc)
{
        struct filedesc *fdp = p->p_fd;
        struct klist *list = NULL;
        uint16_t kq_state;
        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);
        kq_state = kq->kq_state;
        if (knlc) {
                knote_unlock_cancel(kq, kn, knlc, KNOTE_KQ_UNLOCK);
        } else {
                kqunlock(kq);
        }
        if (is_fd)
                proc_fdunlock(p);
        else
                knhash_unlock(p);

        if (kq_state & KQ_DYNAMIC)
                kqueue_release_last(p, kq);
}

/*
 * 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 locked, returns with the kqueue unlocked.
 *
 * If a knote locking context is passed, it is canceled.
 *
 * The knote may have already been detached from
 * (or not yet attached to) its source object.
 */
static void
knote_drop(struct kqueue *kq, struct knote *kn, struct knote_lock_ctx *knlc)
{
        struct proc *p = kq->kq_p;

        kqlock_held(kq);

        assert((kn->kn_status & KN_DROPPING) == 0);
        if (knlc == NULL) {
                assert((kn->kn_status & KN_LOCKED) == 0);
        }
        kn->kn_status |= KN_DROPPING;

        knote_unsuppress(kn);
        knote_dequeue(kn);
        knote_wait_for_filter_events(kq, kn);

        /* If we are attached, disconnect from the source first */
        if (kn->kn_status & KN_ATTACHED) {
                knote_fops(kn)->f_detach(kn);
        }

        /* kq may be freed when kq_remove_knote() returns */
        kq_remove_knote(kq, kn, p, knlc);
        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);
}

/* 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) {
                /*
                 * 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, kn);
        TAILQ_INSERT_TAIL(suppressq, kn, kn_tqe);
}

/* 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;

        kn->kn_status &= ~KN_SUPPRESSED;
        suppressq = kqueue_get_suppressed_queue(kq, kn);
        TAILQ_REMOVE(suppressq, kn, kn_tqe);

        /*
         * If the knote is no longer active, reset its push,
         * and resynchronize kn_qos_index with kn_qos_override
         */
        if ((kn->kn_status & KN_ACTIVE) == 0) {
                kn->kn_qos_override = kn->kn_req_index;
        }
        kn->kn_qos_index = kn->kn_qos_override;

        /* 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) && TAILQ_EMPTY(suppressq)) {
                struct kqworkloop *kqwl = (struct kqworkloop *)kq;

                if (kqworkloop_is_processing_on_current_thread(kqwl)) {
                        /*
                         * kqworkloop_end_processing() or kqworkloop_begin_processing()
                         * will perform the required QoS computations when it unsets the
                         * processing mode.
                         */
                } else {
                        kq_req_lock(kqwl);
                        kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_RESET_WAKEUP_OVERRIDE, 0);
                        kq_req_unlock(kqwl);
                }
        }
}

/* 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);
                TAILQ_INSERT_TAIL(queue, kn, kn_tqe);
                kn->kn_status |= KN_QUEUED;
                kq->kq_count++;
                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--;
}

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();

#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 = ((struct knote *)zalloc(knote_zone));
        bzero(kn, sizeof(struct knote));
        return kn;
}

static void
knote_free(struct knote *kn)
{
        assert(kn->kn_inuse == 0);
        assert((kn->kn_status & KN_LOCKED) == 0);
        zfree(knote_zone, kn);
}

#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 */
        }
        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);
}

static int
event_unlock(struct socket *so, int refcount, void *lr)
{
        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);
}

static int
event_sofreelastref(struct socket *so)
{
        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);
}

static int
kev_attach(struct socket *so, __unused int proto, __unused struct proc *p)
{
        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);
}

static int
kev_detach(struct socket *so)
{
        struct kern_event_pcb *ev_pcb = (struct kern_event_pcb *) so->so_pcb;

        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);

        /*
         * Limit third parties to posting events for registered vendor codes
         * only
         */
        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));
}

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 (total_size > MLEN) {
                OSIncrementAtomic64((SInt64 *)&kevtstat.kes_toobig);
                return (EMSGSIZE);
        }

        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;

        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_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);
        }

        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;
        }

        error = SYSCTL_OUT(req, &kevtstat,
            MIN(sizeof(struct kevtstat), req->oldlen));
done:
        lck_rw_done(kev_rwlock);

        return (error);
}

__private_extern__ int
kevt_pcblist SYSCTL_HANDLER_ARGS
{
#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;

        buf = _MALLOC(item_size, M_TEMP, M_WAITOK | M_ZERO);
        if (buf == NULL)
                return (ENOMEM);

        lck_rw_lock_shared(kev_rwlock);

        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 are done if there is no pcb
         */
        if (n == 0) {
                goto done;
        }

        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);
        }

        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;
                }
        }

done:
        lck_rw_done(kev_rwlock);

        return (error);
}

#endif /* SOCKETS */


int
fill_kqueueinfo(struct kqueue *kq, struct kqueue_info * kinfo)
{
        struct vinfo_stat * st;

        st = &kinfo->kq_stat;

        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;

        /* 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);
}

static int
fill_kqueue_dyninfo(struct kqueue *kq, struct kqueue_dyninfo *kqdi)
{
        struct kqworkloop *kqwl = (struct kqworkloop *)kq;
        struct kqrequest *kqr = &kqwl->kqwl_request;
        workq_threadreq_param_t trp = {};
        int err;

        if ((kq->kq_state & KQ_WORKLOOP) == 0) {
                return EINVAL;
        }

        if ((err = fill_kqueueinfo(kq, &kqdi->kqdi_info))) {
                return err;
        }

        kq_req_lock(kqwl);

        kqdi->kqdi_servicer = thread_tid(kqr->kqr_thread);
        kqdi->kqdi_owner = thread_tid(kqwl->kqwl_owner);
        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 = 0;

        trp.trp_value = kqwl->kqwl_params;
        if (trp.trp_flags & TRP_PRIORITY)
                kqdi->kqdi_pri = trp.trp_pri;
        else
                kqdi->kqdi_pri = 0;

        if (trp.trp_flags & TRP_POLICY)
                kqdi->kqdi_pol = trp.trp_pol;
        else
                kqdi->kqdi_pol = 0;

        if (trp.trp_flags & TRP_CPUPERCENT)
                kqdi->kqdi_cpupercent = trp.trp_cpupercent;
        else
                kqdi->kqdi_cpupercent = 0;

        kq_req_unlock(kqwl);

        return 0;
}


void
knote_markstayactive(struct knote *kn)
{
        struct kqueue *kq = knote_get_kq(kn);
        kq_index_t qos;

        kqlock(kq);
        kn->kn_status |= KN_STAYACTIVE;

        /*
         * 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);
        assert((kn->kn_status & (KN_QUEUED | KN_SUPPRESSED)) == 0);

        /* handle all stayactive knotes on the (appropriate) manager */
        if (kq->kq_state & KQ_WORKQ) {
                qos = KQWQ_QOS_MANAGER;
        } else if (kq->kq_state & KQ_WORKLOOP) {
                struct kqworkloop *kqwl = (struct kqworkloop *)kq;

                qos = _pthread_priority_thread_qos(kn->kn_qos);
                assert(qos && qos < THREAD_QOS_LAST);
                kq_req_lock(kq);
                kqworkloop_update_threads_qos(kqwl, KQWL_UTQ_UPDATE_STAYACTIVE_QOS, qos);
                kq_req_unlock(kq);
                qos = KQWL_BUCKET_STAYACTIVE;
        } else {
                qos = THREAD_QOS_UNSPECIFIED;
        }

        kn->kn_req_index = qos;
        kn->kn_qos_override = qos;
        kn->kn_qos_index = qos;

        knote_activate(kn);
        kqunlock(kq);
}

void
knote_clearstayactive(struct knote *kn)
{
        kqlock(knote_get_kq(kn));
        kn->kn_status &= ~KN_STAYACTIVE;
        knote_deactivate(kn);
        kqunlock(knote_get_kq(kn));
}

static unsigned long
kevent_extinfo_emit(struct kqueue *kq, struct knote *kn, struct kevent_extinfo *buf,
                unsigned long buflen, unsigned long nknotes)
{
        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;

                                kqlock(kq);

                                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;

                                kqunlock(kq);
                        }

                        /* we return total number of knotes, which may be more than requested */
                        nknotes++;
                }
        }

        return nknotes;
}

int
kevent_copyout_proc_dynkqids(void *proc, user_addr_t ubuf, uint32_t ubufsize,
                int32_t *nkqueues_out)
{
        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;

        assert(p != NULL);

        if (ubuf == USER_ADDR_NULL && ubufsize != 0) {
                err = EINVAL;
                goto out;
        }

        buflen = min(ubuflen, PROC_PIDDYNKQUEUES_MAX);

        if (ubuflen != 0) {
                if (os_mul_overflow(sizeof(kqueue_id_t), buflen, &bufsize)) {
                        err = ERANGE;
                        goto out;
                }
                kq_ids = kalloc(bufsize);
                if (!kq_ids) {
                        err = ENOMEM;
                        goto out;
                }
                bzero(kq_ids, bufsize);
        }

        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) {
                                /* report the number of kqueues, even if they don't all fit */
                                if (nkqueues < buflen) {
                                        kq_ids[nkqueues] = kqwl->kqwl_dynamicid;
                                }
                                nkqueues++;
                        }
                }
        }

        kqhash_unlock(p);

        if (kq_ids) {
                size_t copysize;
                if (os_mul_overflow(sizeof(kqueue_id_t), min(buflen, nkqueues), &copysize)) {
                        err = ERANGE;
                        goto out;
                }

                assert(ubufsize >= copysize);
                err = copyout(kq_ids, ubuf, copysize);
        }

out:
        if (kq_ids) {
                kfree(kq_ids, bufsize);
        }

        if (!err) {
                *nkqueues_out = (int)min(nkqueues, PROC_PIDDYNKQUEUES_MAX);
        }
        return err;
}

int
kevent_copyout_dynkqinfo(void *proc, kqueue_id_t kq_id, user_addr_t ubuf,
                uint32_t ubufsize, int32_t *size_out)
{
        proc_t p = (proc_t)proc;
        struct kqueue *kq;
        int err = 0;
        struct kqueue_dyninfo kqdi = { };

        assert(p != NULL);

        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);

        /*
         * 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;
}

int
kevent_copyout_dynkqextinfo(void *proc, kqueue_id_t kq_id, user_addr_t ubuf,
                uint32_t ubufsize, int32_t *nknotes_out)
{
        proc_t p = (proc_t)proc;
        struct kqueue *kq;
        int err;

        assert(p != NULL);

        kqhash_lock(p);
        kq = kqueue_hash_lookup(p, kq_id);
        if (!kq) {
                kqhash_unlock(p);
                return ESRCH;
        }
        kqueue_retain(kq);
        kqhash_unlock(p);

        err = pid_kqueue_extinfo(p, kq, ubuf, ubufsize, nknotes_out);
        kqueue_release_last(p, kq);
        return err;
}

int
pid_kqueue_extinfo(proc_t p, struct kqueue *kq, user_addr_t ubuf,
                uint32_t bufsize, int32_t *retval)
{
        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;

        /* arbitrary upper limit to cap kernel memory usage, copyout size, etc. */
        buflen = min(buflen, PROC_PIDFDKQUEUE_KNOTES_MAX);

        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);

        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);
                }
        }

        assert(bufsize >= sizeof(struct kevent_extinfo) * min(buflen, nknotes));
        err = copyout(kqext, ubuf, sizeof(struct kevent_extinfo) * min(buflen, nknotes));

out:
        if (kqext) {
                kfree(kqext, buflen * sizeof(struct kevent_extinfo));
                kqext = NULL;
        }

        if (!err) {
                *retval = min(nknotes, PROC_PIDFDKQUEUE_KNOTES_MAX);
        }
        return err;
}

static unsigned int
klist_copy_udata(struct klist *list, uint64_t *buf,
                unsigned int buflen, unsigned int nknotes)
{
        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++;
        }

        return nknotes;
}

static unsigned int
kqlist_copy_dynamicids(__assert_only proc_t p, struct kqlist *list,
                uint64_t *buf, unsigned int buflen, unsigned int nids)
{
        kqhash_lock_held(p);
        struct kqworkloop *kqwl;
        SLIST_FOREACH(kqwl, list, kqwl_hashlink) {
                if (nids < buflen) {
                        buf[nids] = kqwl->kqwl_dynamicid;
                }
                nids++;
        }
        return nids;
}

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);

        if (buflen > 0) {
                assert(buf != NULL);
        }

        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);

        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 (int)nuptrs;
}

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_kqr_bound != NULL) {
                ast_flags64 |= R2K_WORKLOOP_PENDING_EVENTS;
        }

        if (ast_flags64 == 0) {
                return;
        }

        if (!(p->p_flag & P_LP64)) {
                ast_flags32 = (uint32_t)ast_flags64;
                assert(ast_flags64 < 0x100000000ull);
        }

        ast_addr = thread_rettokern_addr(thread);
        if (ast_addr == 0) {
                return;
        }

        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);
        }
}

void
kevent_ast(thread_t thread, uint16_t bits)
{
        proc_t p = current_proc();

        if (bits & AST_KEVENT_REDRIVE_THREADREQ) {
                workq_kern_threadreq_redrive(p, WORKQ_THREADREQ_CAN_CREATE_THREADS);
        }
        if (bits & AST_KEVENT_RETURN_TO_KERNEL) {
                kevent_set_return_to_kernel_user_tsd(p, thread);
        }
}

#if DEVELOPMENT || DEBUG

#define KEVENT_SYSCTL_BOUND_ID 1

static int
kevent_sysctl SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2)
        uintptr_t type = (uintptr_t)arg1;
        uint64_t bound_id = 0;

        if (type != KEVENT_SYSCTL_BOUND_ID) {
                return EINVAL;
        }

        if (req->newptr) {
                return EINVAL;
        }

        struct uthread *ut = get_bsdthread_info(current_thread());
        if (!ut) {
                return EFAULT;
        }

        struct kqrequest *kqr = ut->uu_kqr_bound;
        if (kqr) {
                if (kqr->kqr_state & KQR_WORKLOOP) {
                        bound_id = kqr_kqworkloop(kqr)->kqwl_dynamicid;
                } else {
                        bound_id = -1;
                }
        }

        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 */