xnu-4903.270.47.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/syscall.h> // SYS_* constants
#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
#define f_lflags f_fglob->fg_lflags

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, 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, 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;
	fp->f_lflags |= FG_CONFINED;

	proc_fdlock(p);
	*fdflags(p, fd) |= UF_EXCLOSE | UF_FORKCLOSE;
	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;
}

static inline bool
kqueue_threadreq_can_use_ast(struct kqueue *kq)
{
	if (current_proc() == kq->kq_p) {
		/*
		 * Setting an AST from a non BSD syscall is unsafe: mach_msg_trap() can
		 * do combined send/receive and in the case of self-IPC, the AST may bet
		 * set on a thread that will not return to userspace and needs the
		 * thread the AST would create to unblock itself.
		 *
		 * At this time, we really want to target:
		 *
		 * - kevent variants that can cause thread creations, and dispatch
		 *   really only uses kevent_qos and kevent_id,
		 *
		 * - workq_kernreturn (directly about thread creations)
		 *
		 * - bsdthread_ctl which is used for qos changes and has direct impact
		 *   on the creator thread scheduling decisions.
		 */
		switch (current_uthread()->syscall_code) {
		case SYS_kevent_qos:
		case SYS_kevent_id:
		case SYS_workq_kernreturn:
		case SYS_bsdthread_ctl:
			return true;
		}
	}
	return false;
}

/*
 * 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 (kqueue_threadreq_can_use_ast(kq)) {
		flags |= WORKQ_THREADREQ_SET_AST_ON_FAILURE;
	}
	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 (kqueue_threadreq_can_use_ast(kq)) {
		flags |= WORKQ_THREADREQ_SET_AST_ON_FAILURE;
	}
	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, bool make_active)
{
	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 (__probable(kn->kn_status & KN_REQVANISH)) {
			/*
			 * If EV_VANISH supported - prepare to deliver one
			 */
			kn->kn_status |= KN_VANISHED;
		} else {
			/*
			 * Handle the legacy way to indicate that the port/portset was
			 * deallocated or left the current Mach portspace (modern technique
			 * is with an EV_VANISHED protocol).
			 *
			 * Deliver an EV_EOF event for these changes (hopefully it will get
			 * delivered before the port name recycles to the same generation
			 * count and someone tries to re-register a kevent for it or the
			 * events are udata-specific - avoiding a conflict).
			 */
			kn->kn_flags |= EV_EOF | EV_ONESHOT;
		}
		if (make_active) {
			knote_activate(kn);
		}
		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 */