Index: head/sys/kern/kern_event.c
===================================================================
--- head/sys/kern/kern_event.c	(revision 295784)
+++ head/sys/kern/kern_event.c	(revision 295785)
@@ -1,2458 +1,2461 @@
 /*-
  * Copyright (c) 1999,2000,2001 Jonathan Lemon <jlemon@FreeBSD.org>
  * Copyright 2004 John-Mark Gurney <jmg@FreeBSD.org>
  * Copyright (c) 2009 Apple, Inc.
  * 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.
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include "opt_ktrace.h"
 #include "opt_kqueue.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/capsicum.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/rwlock.h>
 #include <sys/proc.h>
 #include <sys/malloc.h>
 #include <sys/unistd.h>
 #include <sys/file.h>
 #include <sys/filedesc.h>
 #include <sys/filio.h>
 #include <sys/fcntl.h>
 #include <sys/kthread.h>
 #include <sys/selinfo.h>
 #include <sys/stdatomic.h>
 #include <sys/queue.h>
 #include <sys/event.h>
 #include <sys/eventvar.h>
 #include <sys/poll.h>
 #include <sys/protosw.h>
 #include <sys/resourcevar.h>
 #include <sys/sigio.h>
 #include <sys/signalvar.h>
 #include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/stat.h>
 #include <sys/sysctl.h>
 #include <sys/sysproto.h>
 #include <sys/syscallsubr.h>
 #include <sys/taskqueue.h>
 #include <sys/uio.h>
 #include <sys/user.h>
 #ifdef KTRACE
 #include <sys/ktrace.h>
 #endif
 
 #include <vm/uma.h>
 
 static MALLOC_DEFINE(M_KQUEUE, "kqueue", "memory for kqueue system");
 
 /*
  * This lock is used if multiple kq locks are required.  This possibly
  * should be made into a per proc lock.
  */
 static struct mtx	kq_global;
 MTX_SYSINIT(kq_global, &kq_global, "kqueue order", MTX_DEF);
 #define KQ_GLOBAL_LOCK(lck, haslck)	do {	\
 	if (!haslck)				\
 		mtx_lock(lck);			\
 	haslck = 1;				\
 } while (0)
 #define KQ_GLOBAL_UNLOCK(lck, haslck)	do {	\
 	if (haslck)				\
 		mtx_unlock(lck);			\
 	haslck = 0;				\
 } while (0)
 
 TASKQUEUE_DEFINE_THREAD(kqueue);
 
 static int	kevent_copyout(void *arg, struct kevent *kevp, int count);
 static int	kevent_copyin(void *arg, struct kevent *kevp, int count);
 static int	kqueue_register(struct kqueue *kq, struct kevent *kev,
 		    struct thread *td, int waitok);
 static int	kqueue_acquire(struct file *fp, struct kqueue **kqp);
 static void	kqueue_release(struct kqueue *kq, int locked);
 static void	kqueue_destroy(struct kqueue *kq);
 static void	kqueue_drain(struct kqueue *kq, struct thread *td);
 static int	kqueue_expand(struct kqueue *kq, struct filterops *fops,
 		    uintptr_t ident, int waitok);
 static void	kqueue_task(void *arg, int pending);
 static int	kqueue_scan(struct kqueue *kq, int maxevents,
 		    struct kevent_copyops *k_ops,
 		    const struct timespec *timeout,
 		    struct kevent *keva, struct thread *td);
 static void 	kqueue_wakeup(struct kqueue *kq);
 static struct filterops *kqueue_fo_find(int filt);
 static void	kqueue_fo_release(int filt);
 
 static fo_ioctl_t	kqueue_ioctl;
 static fo_poll_t	kqueue_poll;
 static fo_kqfilter_t	kqueue_kqfilter;
 static fo_stat_t	kqueue_stat;
 static fo_close_t	kqueue_close;
 static fo_fill_kinfo_t	kqueue_fill_kinfo;
 
 static struct fileops kqueueops = {
 	.fo_read = invfo_rdwr,
 	.fo_write = invfo_rdwr,
 	.fo_truncate = invfo_truncate,
 	.fo_ioctl = kqueue_ioctl,
 	.fo_poll = kqueue_poll,
 	.fo_kqfilter = kqueue_kqfilter,
 	.fo_stat = kqueue_stat,
 	.fo_close = kqueue_close,
 	.fo_chmod = invfo_chmod,
 	.fo_chown = invfo_chown,
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = kqueue_fill_kinfo,
 };
 
 static int 	knote_attach(struct knote *kn, struct kqueue *kq);
 static void 	knote_drop(struct knote *kn, struct thread *td);
 static void 	knote_enqueue(struct knote *kn);
 static void 	knote_dequeue(struct knote *kn);
 static void 	knote_init(void);
 static struct 	knote *knote_alloc(int waitok);
 static void 	knote_free(struct knote *kn);
 
 static void	filt_kqdetach(struct knote *kn);
 static int	filt_kqueue(struct knote *kn, long hint);
 static int	filt_procattach(struct knote *kn);
 static void	filt_procdetach(struct knote *kn);
 static int	filt_proc(struct knote *kn, long hint);
 static int	filt_fileattach(struct knote *kn);
 static void	filt_timerexpire(void *knx);
 static int	filt_timerattach(struct knote *kn);
 static void	filt_timerdetach(struct knote *kn);
 static int	filt_timer(struct knote *kn, long hint);
 static int	filt_userattach(struct knote *kn);
 static void	filt_userdetach(struct knote *kn);
 static int	filt_user(struct knote *kn, long hint);
 static void	filt_usertouch(struct knote *kn, struct kevent *kev,
 		    u_long type);
 
 static struct filterops file_filtops = {
 	.f_isfd = 1,
 	.f_attach = filt_fileattach,
 };
 static struct filterops kqread_filtops = {
 	.f_isfd = 1,
 	.f_detach = filt_kqdetach,
 	.f_event = filt_kqueue,
 };
 /* XXX - move to kern_proc.c?  */
 static struct filterops proc_filtops = {
 	.f_isfd = 0,
 	.f_attach = filt_procattach,
 	.f_detach = filt_procdetach,
 	.f_event = filt_proc,
 };
 static struct filterops timer_filtops = {
 	.f_isfd = 0,
 	.f_attach = filt_timerattach,
 	.f_detach = filt_timerdetach,
 	.f_event = filt_timer,
 };
 static struct filterops user_filtops = {
 	.f_attach = filt_userattach,
 	.f_detach = filt_userdetach,
 	.f_event = filt_user,
 	.f_touch = filt_usertouch,
 };
 
 static uma_zone_t	knote_zone;
 static atomic_uint	kq_ncallouts = ATOMIC_VAR_INIT(0);
 static unsigned int 	kq_calloutmax = 4 * 1024;
 SYSCTL_UINT(_kern, OID_AUTO, kq_calloutmax, CTLFLAG_RW,
     &kq_calloutmax, 0, "Maximum number of callouts allocated for kqueue");
 
 /* XXX - ensure not KN_INFLUX?? */
 #define KNOTE_ACTIVATE(kn, islock) do { 				\
 	if ((islock))							\
 		mtx_assert(&(kn)->kn_kq->kq_lock, MA_OWNED);		\
 	else								\
 		KQ_LOCK((kn)->kn_kq);					\
 	(kn)->kn_status |= KN_ACTIVE;					\
 	if (((kn)->kn_status & (KN_QUEUED | KN_DISABLED)) == 0)		\
 		knote_enqueue((kn));					\
 	if (!(islock))							\
 		KQ_UNLOCK((kn)->kn_kq);					\
 } while(0)
 #define KQ_LOCK(kq) do {						\
 	mtx_lock(&(kq)->kq_lock);					\
 } while (0)
 #define KQ_FLUX_WAKEUP(kq) do {						\
 	if (((kq)->kq_state & KQ_FLUXWAIT) == KQ_FLUXWAIT) {		\
 		(kq)->kq_state &= ~KQ_FLUXWAIT;				\
 		wakeup((kq));						\
 	}								\
 } while (0)
 #define KQ_UNLOCK_FLUX(kq) do {						\
 	KQ_FLUX_WAKEUP(kq);						\
 	mtx_unlock(&(kq)->kq_lock);					\
 } while (0)
 #define KQ_UNLOCK(kq) do {						\
 	mtx_unlock(&(kq)->kq_lock);					\
 } while (0)
 #define KQ_OWNED(kq) do {						\
 	mtx_assert(&(kq)->kq_lock, MA_OWNED);				\
 } while (0)
 #define KQ_NOTOWNED(kq) do {						\
 	mtx_assert(&(kq)->kq_lock, MA_NOTOWNED);			\
 } while (0)
 #define KN_LIST_LOCK(kn) do {						\
 	if (kn->kn_knlist != NULL)					\
 		kn->kn_knlist->kl_lock(kn->kn_knlist->kl_lockarg);	\
 } while (0)
 #define KN_LIST_UNLOCK(kn) do {						\
 	if (kn->kn_knlist != NULL) 					\
 		kn->kn_knlist->kl_unlock(kn->kn_knlist->kl_lockarg);	\
 } while (0)
 #define	KNL_ASSERT_LOCK(knl, islocked) do {				\
 	if (islocked)							\
 		KNL_ASSERT_LOCKED(knl);				\
 	else								\
 		KNL_ASSERT_UNLOCKED(knl);				\
 } while (0)
 #ifdef INVARIANTS
 #define	KNL_ASSERT_LOCKED(knl) do {					\
 	knl->kl_assert_locked((knl)->kl_lockarg);			\
 } while (0)
 #define	KNL_ASSERT_UNLOCKED(knl) do {					\
 	knl->kl_assert_unlocked((knl)->kl_lockarg);			\
 } while (0)
 #else /* !INVARIANTS */
 #define	KNL_ASSERT_LOCKED(knl) do {} while(0)
 #define	KNL_ASSERT_UNLOCKED(knl) do {} while (0)
 #endif /* INVARIANTS */
 
 #ifndef	KN_HASHSIZE
 #define	KN_HASHSIZE		64		/* XXX should be tunable */
 #endif
 
 #define KN_HASH(val, mask)	(((val) ^ (val >> 8)) & (mask))
 
 static int
 filt_nullattach(struct knote *kn)
 {
 
 	return (ENXIO);
 };
 
 struct filterops null_filtops = {
 	.f_isfd = 0,
 	.f_attach = filt_nullattach,
 };
 
 /* XXX - make SYSINIT to add these, and move into respective modules. */
 extern struct filterops sig_filtops;
 extern struct filterops fs_filtops;
 
 /*
  * Table for for all system-defined filters.
  */
 static struct mtx	filterops_lock;
 MTX_SYSINIT(kqueue_filterops, &filterops_lock, "protect sysfilt_ops",
 	MTX_DEF);
 static struct {
 	struct filterops *for_fop;
 	int for_nolock;
 	int for_refcnt;
 } sysfilt_ops[EVFILT_SYSCOUNT] = {
 	{ &file_filtops, 1 },			/* EVFILT_READ */
 	{ &file_filtops, 1 },			/* EVFILT_WRITE */
 	{ &null_filtops },			/* EVFILT_AIO */
 	{ &file_filtops, 1 },			/* EVFILT_VNODE */
 	{ &proc_filtops, 1 },			/* EVFILT_PROC */
 	{ &sig_filtops, 1 },			/* EVFILT_SIGNAL */
 	{ &timer_filtops, 1 },			/* EVFILT_TIMER */
 	{ &file_filtops, 1 },			/* EVFILT_PROCDESC */
 	{ &fs_filtops, 1 },			/* EVFILT_FS */
 	{ &null_filtops },			/* EVFILT_LIO */
 	{ &user_filtops, 1 },			/* EVFILT_USER */
 	{ &null_filtops },			/* EVFILT_SENDFILE */
 };
 
 /*
  * Simple redirection for all cdevsw style objects to call their fo_kqfilter
  * method.
  */
 static int
 filt_fileattach(struct knote *kn)
 {
 
 	return (fo_kqfilter(kn->kn_fp, kn));
 }
 
 /*ARGSUSED*/
 static int
 kqueue_kqfilter(struct file *fp, struct knote *kn)
 {
 	struct kqueue *kq = kn->kn_fp->f_data;
 
 	if (kn->kn_filter != EVFILT_READ)
 		return (EINVAL);
 
 	kn->kn_status |= KN_KQUEUE;
 	kn->kn_fop = &kqread_filtops;
 	knlist_add(&kq->kq_sel.si_note, kn, 0);
 
 	return (0);
 }
 
 static void
 filt_kqdetach(struct knote *kn)
 {
 	struct kqueue *kq = kn->kn_fp->f_data;
 
 	knlist_remove(&kq->kq_sel.si_note, kn, 0);
 }
 
 /*ARGSUSED*/
 static int
 filt_kqueue(struct knote *kn, long hint)
 {
 	struct kqueue *kq = kn->kn_fp->f_data;
 
 	kn->kn_data = kq->kq_count;
 	return (kn->kn_data > 0);
 }
 
 /* XXX - move to kern_proc.c?  */
 static int
 filt_procattach(struct knote *kn)
 {
 	struct proc *p;
 	int immediate;
 	int error;
 
 	immediate = 0;
 	p = pfind(kn->kn_id);
 	if (p == NULL && (kn->kn_sfflags & NOTE_EXIT)) {
 		p = zpfind(kn->kn_id);
 		immediate = 1;
 	} else if (p != NULL && (p->p_flag & P_WEXIT)) {
 		immediate = 1;
 	}
 
 	if (p == NULL)
 		return (ESRCH);
 	if ((error = p_cansee(curthread, p))) {
 		PROC_UNLOCK(p);
 		return (error);
 	}
 
 	kn->kn_ptr.p_proc = p;
 	kn->kn_flags |= EV_CLEAR;		/* automatically set */
 
 	/*
 	 * Internal flag indicating registration done by kernel for the
 	 * purposes of getting a NOTE_CHILD notification.
 	 */
 	if (kn->kn_flags & EV_FLAG2) {
 		kn->kn_flags &= ~EV_FLAG2;
 		kn->kn_data = kn->kn_sdata;		/* ppid */
 		kn->kn_fflags = NOTE_CHILD;
                 kn->kn_sfflags &= ~NOTE_EXIT;
 		immediate = 1; /* Force immediate activation of child note. */
 	}
 	/*
 	 * Internal flag indicating registration done by kernel (for other than
 	 * NOTE_CHILD).
 	 */
 	if (kn->kn_flags & EV_FLAG1) {
 		kn->kn_flags &= ~EV_FLAG1;
 	}
 
 	if (immediate == 0)
 		knlist_add(&p->p_klist, kn, 1);
 
 	/*
 	 * Immediately activate any child notes or, in the case of a zombie
 	 * target process, exit notes.  The latter is necessary to handle the
 	 * case where the target process, e.g. a child, dies before the kevent
 	 * is registered.
 	 */
 	if (immediate && filt_proc(kn, NOTE_EXIT))
 		KNOTE_ACTIVATE(kn, 0);
 
 	PROC_UNLOCK(p);
 
 	return (0);
 }
 
 /*
  * The knote may be attached to a different process, which may exit,
  * leaving nothing for the knote to be attached to.  So when the process
  * exits, the knote is marked as DETACHED and also flagged as ONESHOT so
  * it will be deleted when read out.  However, as part of the knote deletion,
  * this routine is called, so a check is needed to avoid actually performing
  * a detach, because the original process does not exist any more.
  */
 /* XXX - move to kern_proc.c?  */
 static void
 filt_procdetach(struct knote *kn)
 {
 	struct proc *p;
 
 	p = kn->kn_ptr.p_proc;
 	knlist_remove(&p->p_klist, kn, 0);
 	kn->kn_ptr.p_proc = NULL;
 }
 
 /* XXX - move to kern_proc.c?  */
 static int
 filt_proc(struct knote *kn, long hint)
 {
 	struct proc *p;
 	u_int event;
 
 	p = kn->kn_ptr.p_proc;
 	/* Mask off extra data. */
 	event = (u_int)hint & NOTE_PCTRLMASK;
 
 	/* If the user is interested in this event, record it. */
 	if (kn->kn_sfflags & event)
 		kn->kn_fflags |= event;
 
 	/* Process is gone, so flag the event as finished. */
 	if (event == NOTE_EXIT) {
 		if (!(kn->kn_status & KN_DETACHED))
 			knlist_remove_inevent(&p->p_klist, kn);
 		kn->kn_flags |= EV_EOF | EV_ONESHOT;
 		kn->kn_ptr.p_proc = NULL;
 		if (kn->kn_fflags & NOTE_EXIT)
 			kn->kn_data = KW_EXITCODE(p->p_xexit, p->p_xsig);
 		if (kn->kn_fflags == 0)
 			kn->kn_flags |= EV_DROP;
 		return (1);
 	}
 
 	return (kn->kn_fflags != 0);
 }
 
 /*
  * Called when the process forked. It mostly does the same as the
  * knote(), activating all knotes registered to be activated when the
  * process forked. Additionally, for each knote attached to the
  * parent, check whether user wants to track the new process. If so
  * attach a new knote to it, and immediately report an event with the
  * child's pid.
  */
 void
 knote_fork(struct knlist *list, int pid)
 {
 	struct kqueue *kq;
 	struct knote *kn;
 	struct kevent kev;
 	int error;
 
 	if (list == NULL)
 		return;
 	list->kl_lock(list->kl_lockarg);
 
 	SLIST_FOREACH(kn, &list->kl_list, kn_selnext) {
 		/*
 		 * XXX - Why do we skip the kn if it is _INFLUX?  Does this
 		 * mean we will not properly wake up some notes?
 		 */
 		if ((kn->kn_status & KN_INFLUX) == KN_INFLUX)
 			continue;
 		kq = kn->kn_kq;
 		KQ_LOCK(kq);
 		if ((kn->kn_status & (KN_INFLUX | KN_SCAN)) == KN_INFLUX) {
 			KQ_UNLOCK(kq);
 			continue;
 		}
 
 		/*
 		 * The same as knote(), activate the event.
 		 */
 		if ((kn->kn_sfflags & NOTE_TRACK) == 0) {
 			kn->kn_status |= KN_HASKQLOCK;
 			if (kn->kn_fop->f_event(kn, NOTE_FORK))
 				KNOTE_ACTIVATE(kn, 1);
 			kn->kn_status &= ~KN_HASKQLOCK;
 			KQ_UNLOCK(kq);
 			continue;
 		}
 
 		/*
 		 * The NOTE_TRACK case. In addition to the activation
 		 * of the event, we need to register new events to
 		 * track the child. Drop the locks in preparation for
 		 * the call to kqueue_register().
 		 */
 		kn->kn_status |= KN_INFLUX;
 		KQ_UNLOCK(kq);
 		list->kl_unlock(list->kl_lockarg);
 
 		/*
 		 * Activate existing knote and register tracking knotes with
 		 * new process.
 		 *
 		 * First register a knote to get just the child notice. This
 		 * must be a separate note from a potential NOTE_EXIT
 		 * notification since both NOTE_CHILD and NOTE_EXIT are defined
 		 * to use the data field (in conflicting ways).
 		 */
 		kev.ident = pid;
 		kev.filter = kn->kn_filter;
 		kev.flags = kn->kn_flags | EV_ADD | EV_ENABLE | EV_ONESHOT | EV_FLAG2;
 		kev.fflags = kn->kn_sfflags;
 		kev.data = kn->kn_id;		/* parent */
 		kev.udata = kn->kn_kevent.udata;/* preserve udata */
 		error = kqueue_register(kq, &kev, NULL, 0);
 		if (error)
 			kn->kn_fflags |= NOTE_TRACKERR;
 
 		/*
 		 * Then register another knote to track other potential events
 		 * from the new process.
 		 */
 		kev.ident = pid;
 		kev.filter = kn->kn_filter;
 		kev.flags = kn->kn_flags | EV_ADD | EV_ENABLE | EV_FLAG1;
 		kev.fflags = kn->kn_sfflags;
 		kev.data = kn->kn_id;		/* parent */
 		kev.udata = kn->kn_kevent.udata;/* preserve udata */
 		error = kqueue_register(kq, &kev, NULL, 0);
 		if (error)
 			kn->kn_fflags |= NOTE_TRACKERR;
 		if (kn->kn_fop->f_event(kn, NOTE_FORK))
 			KNOTE_ACTIVATE(kn, 0);
 		KQ_LOCK(kq);
 		kn->kn_status &= ~KN_INFLUX;
 		KQ_UNLOCK_FLUX(kq);
 		list->kl_lock(list->kl_lockarg);
 	}
 	list->kl_unlock(list->kl_lockarg);
 }
 
 /*
  * XXX: EVFILT_TIMER should perhaps live in kern_time.c beside the
  * interval timer support code.
  */
 
 #define NOTE_TIMER_PRECMASK	(NOTE_SECONDS|NOTE_MSECONDS|NOTE_USECONDS| \
 				NOTE_NSECONDS)
 
 static __inline sbintime_t
 timer2sbintime(intptr_t data, int flags)
 {
 	sbintime_t modifier;
 
 	switch (flags & NOTE_TIMER_PRECMASK) {
 	case NOTE_SECONDS:
 		modifier = SBT_1S;
 		break;
 	case NOTE_MSECONDS: /* FALLTHROUGH */
 	case 0:
 		modifier = SBT_1MS;
 		break;
 	case NOTE_USECONDS:
 		modifier = SBT_1US;
 		break;
 	case NOTE_NSECONDS:
 		modifier = SBT_1NS;
 		break;
 	default:
 		return (-1);
 	}
 
 #ifdef __LP64__
 	if (data > SBT_MAX / modifier)
 		return (SBT_MAX);
 #endif
 	return (modifier * data);
 }
 
 static void
 filt_timerexpire(void *knx)
 {
 	struct callout *calloutp;
 	struct knote *kn;
 
 	kn = knx;
 	kn->kn_data++;
 	KNOTE_ACTIVATE(kn, 0);	/* XXX - handle locking */
 
 	if ((kn->kn_flags & EV_ONESHOT) != EV_ONESHOT) {
 		calloutp = (struct callout *)kn->kn_hook;
 		*kn->kn_ptr.p_nexttime += timer2sbintime(kn->kn_sdata, 
 		    kn->kn_sfflags);
 		callout_reset_sbt_on(calloutp, *kn->kn_ptr.p_nexttime, 0,
 		    filt_timerexpire, kn, PCPU_GET(cpuid), C_ABSOLUTE);
 	}
 }
 
 /*
  * data contains amount of time to sleep
  */
 static int
 filt_timerattach(struct knote *kn)
 {
 	struct callout *calloutp;
 	sbintime_t to;
 	unsigned int ncallouts;
 
 	if ((intptr_t)kn->kn_sdata < 0)
 		return (EINVAL);
 	if ((intptr_t)kn->kn_sdata == 0 && (kn->kn_flags & EV_ONESHOT) == 0)
 		kn->kn_sdata = 1;
 	/* Only precision unit are supported in flags so far */
 	if (kn->kn_sfflags & ~NOTE_TIMER_PRECMASK)
 		return (EINVAL);
 
 	to = timer2sbintime(kn->kn_sdata, kn->kn_sfflags);
 	if (to < 0)
 		return (EINVAL);
 
 	ncallouts = atomic_load_explicit(&kq_ncallouts, memory_order_relaxed);
 	do {
 		if (ncallouts >= kq_calloutmax)
 			return (ENOMEM);
 	} while (!atomic_compare_exchange_weak_explicit(&kq_ncallouts,
 	    &ncallouts, ncallouts + 1, memory_order_relaxed,
 	    memory_order_relaxed));
 
 	kn->kn_flags |= EV_CLEAR;		/* automatically set */
 	kn->kn_status &= ~KN_DETACHED;		/* knlist_add clears it */
 	kn->kn_ptr.p_nexttime = malloc(sizeof(sbintime_t), M_KQUEUE, M_WAITOK);
 	calloutp = malloc(sizeof(*calloutp), M_KQUEUE, M_WAITOK);
 	callout_init(calloutp, 1);
 	kn->kn_hook = calloutp;
 	*kn->kn_ptr.p_nexttime = to + sbinuptime();
 	callout_reset_sbt_on(calloutp, *kn->kn_ptr.p_nexttime, 0,
 	    filt_timerexpire, kn, PCPU_GET(cpuid), C_ABSOLUTE);
 
 	return (0);
 }
 
 static void
 filt_timerdetach(struct knote *kn)
 {
 	struct callout *calloutp;
 	unsigned int old;
 
 	calloutp = (struct callout *)kn->kn_hook;
 	callout_drain(calloutp);
 	free(calloutp, M_KQUEUE);
 	free(kn->kn_ptr.p_nexttime, M_KQUEUE);
 	old = atomic_fetch_sub_explicit(&kq_ncallouts, 1, memory_order_relaxed);
 	KASSERT(old > 0, ("Number of callouts cannot become negative"));
 	kn->kn_status |= KN_DETACHED;	/* knlist_remove sets it */
 }
 
 static int
 filt_timer(struct knote *kn, long hint)
 {
 
 	return (kn->kn_data != 0);
 }
 
 static int
 filt_userattach(struct knote *kn)
 {
 
 	/* 
 	 * EVFILT_USER knotes are not attached to anything in the kernel.
 	 */ 
 	kn->kn_hook = NULL;
 	if (kn->kn_fflags & NOTE_TRIGGER)
 		kn->kn_hookid = 1;
 	else
 		kn->kn_hookid = 0;
 	return (0);
 }
 
 static void
 filt_userdetach(__unused struct knote *kn)
 {
 
 	/*
 	 * EVFILT_USER knotes are not attached to anything in the kernel.
 	 */
 }
 
 static int
 filt_user(struct knote *kn, __unused long hint)
 {
 
 	return (kn->kn_hookid);
 }
 
 static void
 filt_usertouch(struct knote *kn, struct kevent *kev, u_long type)
 {
 	u_int ffctrl;
 
 	switch (type) {
 	case EVENT_REGISTER:
 		if (kev->fflags & NOTE_TRIGGER)
 			kn->kn_hookid = 1;
 
 		ffctrl = kev->fflags & NOTE_FFCTRLMASK;
 		kev->fflags &= NOTE_FFLAGSMASK;
 		switch (ffctrl) {
 		case NOTE_FFNOP:
 			break;
 
 		case NOTE_FFAND:
 			kn->kn_sfflags &= kev->fflags;
 			break;
 
 		case NOTE_FFOR:
 			kn->kn_sfflags |= kev->fflags;
 			break;
 
 		case NOTE_FFCOPY:
 			kn->kn_sfflags = kev->fflags;
 			break;
 
 		default:
 			/* XXX Return error? */
 			break;
 		}
 		kn->kn_sdata = kev->data;
 		if (kev->flags & EV_CLEAR) {
 			kn->kn_hookid = 0;
 			kn->kn_data = 0;
 			kn->kn_fflags = 0;
 		}
 		break;
 
         case EVENT_PROCESS:
 		*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;
 		}
 		break;
 
 	default:
 		panic("filt_usertouch() - invalid type (%ld)", type);
 		break;
 	}
 }
 
 int
 sys_kqueue(struct thread *td, struct kqueue_args *uap)
 {
 
 	return (kern_kqueue(td, 0, NULL));
 }
 
 static void
 kqueue_init(struct kqueue *kq)
 {
 
 	mtx_init(&kq->kq_lock, "kqueue", NULL, MTX_DEF | MTX_DUPOK);
 	TAILQ_INIT(&kq->kq_head);
 	knlist_init_mtx(&kq->kq_sel.si_note, &kq->kq_lock);
 	TASK_INIT(&kq->kq_task, 0, kqueue_task, kq);
 }
 
 int
 kern_kqueue(struct thread *td, int flags, struct filecaps *fcaps)
 {
 	struct filedesc *fdp;
 	struct kqueue *kq;
 	struct file *fp;
 	struct ucred *cred;
 	int fd, error;
 
 	fdp = td->td_proc->p_fd;
 	cred = td->td_ucred;
 	if (!chgkqcnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_KQUEUES)))
 		return (ENOMEM);
 
 	error = falloc_caps(td, &fp, &fd, flags, fcaps);
 	if (error != 0) {
 		chgkqcnt(cred->cr_ruidinfo, -1, 0);
 		return (error);
 	}
 
 	/* An extra reference on `fp' has been held for us by falloc(). */
 	kq = malloc(sizeof *kq, M_KQUEUE, M_WAITOK | M_ZERO);
 	kqueue_init(kq);
 	kq->kq_fdp = fdp;
 	kq->kq_cred = crhold(cred);
 
 	FILEDESC_XLOCK(fdp);
 	TAILQ_INSERT_HEAD(&fdp->fd_kqlist, kq, kq_list);
 	FILEDESC_XUNLOCK(fdp);
 
 	finit(fp, FREAD | FWRITE, DTYPE_KQUEUE, kq, &kqueueops);
 	fdrop(fp, td);
 
 	td->td_retval[0] = fd;
 	return (0);
 }
 
 #ifndef _SYS_SYSPROTO_H_
 struct kevent_args {
 	int	fd;
 	const struct kevent *changelist;
 	int	nchanges;
 	struct	kevent *eventlist;
 	int	nevents;
 	const struct timespec *timeout;
 };
 #endif
 int
 sys_kevent(struct thread *td, struct kevent_args *uap)
 {
 	struct timespec ts, *tsp;
 	struct kevent_copyops k_ops = { uap,
 					kevent_copyout,
 					kevent_copyin};
 	int error;
 #ifdef KTRACE
 	struct uio ktruio;
 	struct iovec ktriov;
 	struct uio *ktruioin = NULL;
 	struct uio *ktruioout = NULL;
 #endif
 
 	if (uap->timeout != NULL) {
 		error = copyin(uap->timeout, &ts, sizeof(ts));
 		if (error)
 			return (error);
 		tsp = &ts;
 	} else
 		tsp = NULL;
 
 #ifdef KTRACE
 	if (KTRPOINT(td, KTR_GENIO)) {
 		ktriov.iov_base = uap->changelist;
 		ktriov.iov_len = uap->nchanges * sizeof(struct kevent);
 		ktruio = (struct uio){ .uio_iov = &ktriov, .uio_iovcnt = 1,
 		    .uio_segflg = UIO_USERSPACE, .uio_rw = UIO_READ,
 		    .uio_td = td };
 		ktruioin = cloneuio(&ktruio);
 		ktriov.iov_base = uap->eventlist;
 		ktriov.iov_len = uap->nevents * sizeof(struct kevent);
 		ktruioout = cloneuio(&ktruio);
 	}
 #endif
 
 	error = kern_kevent(td, uap->fd, uap->nchanges, uap->nevents,
 	    &k_ops, tsp);
 
 #ifdef KTRACE
 	if (ktruioin != NULL) {
 		ktruioin->uio_resid = uap->nchanges * sizeof(struct kevent);
 		ktrgenio(uap->fd, UIO_WRITE, ktruioin, 0);
 		ktruioout->uio_resid = td->td_retval[0] * sizeof(struct kevent);
 		ktrgenio(uap->fd, UIO_READ, ktruioout, error);
 	}
 #endif
 
 	return (error);
 }
 
 /*
  * Copy 'count' items into the destination list pointed to by uap->eventlist.
  */
 static int
 kevent_copyout(void *arg, struct kevent *kevp, int count)
 {
 	struct kevent_args *uap;
 	int error;
 
 	KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
 	uap = (struct kevent_args *)arg;
 
 	error = copyout(kevp, uap->eventlist, count * sizeof *kevp);
 	if (error == 0)
 		uap->eventlist += count;
 	return (error);
 }
 
 /*
  * Copy 'count' items from the list pointed to by uap->changelist.
  */
 static int
 kevent_copyin(void *arg, struct kevent *kevp, int count)
 {
 	struct kevent_args *uap;
 	int error;
 
 	KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
 	uap = (struct kevent_args *)arg;
 
 	error = copyin(uap->changelist, kevp, count * sizeof *kevp);
 	if (error == 0)
 		uap->changelist += count;
 	return (error);
 }
 
 int
 kern_kevent(struct thread *td, int fd, int nchanges, int nevents,
     struct kevent_copyops *k_ops, const struct timespec *timeout)
 {
 	cap_rights_t rights;
 	struct file *fp;
 	int error;
 
 	cap_rights_init(&rights);
 	if (nchanges > 0)
 		cap_rights_set(&rights, CAP_KQUEUE_CHANGE);
 	if (nevents > 0)
 		cap_rights_set(&rights, CAP_KQUEUE_EVENT);
 	error = fget(td, fd, &rights, &fp);
 	if (error != 0)
 		return (error);
 
 	error = kern_kevent_fp(td, fp, nchanges, nevents, k_ops, timeout);
 	fdrop(fp, td);
 
 	return (error);
 }
 
 static int
 kqueue_kevent(struct kqueue *kq, struct thread *td, int nchanges, int nevents,
     struct kevent_copyops *k_ops, const struct timespec *timeout)
 {
 	struct kevent keva[KQ_NEVENTS];
 	struct kevent *kevp, *changes;
 	int i, n, nerrors, error;
 
 	nerrors = 0;
 	while (nchanges > 0) {
 		n = nchanges > KQ_NEVENTS ? KQ_NEVENTS : nchanges;
 		error = k_ops->k_copyin(k_ops->arg, keva, n);
 		if (error)
 			return (error);
 		changes = keva;
 		for (i = 0; i < n; i++) {
 			kevp = &changes[i];
 			if (!kevp->filter)
 				continue;
 			kevp->flags &= ~EV_SYSFLAGS;
 			error = kqueue_register(kq, kevp, td, 1);
 			if (error || (kevp->flags & EV_RECEIPT)) {
 				if (nevents == 0)
 					return (error);
 				kevp->flags = EV_ERROR;
 				kevp->data = error;
 				(void)k_ops->k_copyout(k_ops->arg, kevp, 1);
 				nevents--;
 				nerrors++;
 			}
 		}
 		nchanges -= n;
 	}
 	if (nerrors) {
 		td->td_retval[0] = nerrors;
 		return (0);
 	}
 
 	return (kqueue_scan(kq, nevents, k_ops, timeout, keva, td));
 }
 
 int
 kern_kevent_fp(struct thread *td, struct file *fp, int nchanges, int nevents,
     struct kevent_copyops *k_ops, const struct timespec *timeout)
 {
 	struct kqueue *kq;
 	int error;
 
 	error = kqueue_acquire(fp, &kq);
 	if (error != 0)
 		return (error);
 	error = kqueue_kevent(kq, td, nchanges, nevents, k_ops, timeout);
 	kqueue_release(kq, 0);
 	return (error);
 }
 
 /*
  * Performs a kevent() call on a temporarily created kqueue. This can be
  * used to perform one-shot polling, similar to poll() and select().
  */
 int
 kern_kevent_anonymous(struct thread *td, int nevents,
     struct kevent_copyops *k_ops)
 {
 	struct kqueue kq = {};
 	int error;
 
 	kqueue_init(&kq);
 	kq.kq_refcnt = 1;
 	error = kqueue_kevent(&kq, td, nevents, nevents, k_ops, NULL);
 	kqueue_drain(&kq, td);
 	kqueue_destroy(&kq);
 	return (error);
 }
 
 int
 kqueue_add_filteropts(int filt, struct filterops *filtops)
 {
 	int error;
 
 	error = 0;
 	if (filt > 0 || filt + EVFILT_SYSCOUNT < 0) {
 		printf(
 "trying to add a filterop that is out of range: %d is beyond %d\n",
 		    ~filt, EVFILT_SYSCOUNT);
 		return EINVAL;
 	}
 	mtx_lock(&filterops_lock);
 	if (sysfilt_ops[~filt].for_fop != &null_filtops &&
 	    sysfilt_ops[~filt].for_fop != NULL)
 		error = EEXIST;
 	else {
 		sysfilt_ops[~filt].for_fop = filtops;
 		sysfilt_ops[~filt].for_refcnt = 0;
 	}
 	mtx_unlock(&filterops_lock);
 
 	return (error);
 }
 
 int
 kqueue_del_filteropts(int filt)
 {
 	int error;
 
 	error = 0;
 	if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
 		return EINVAL;
 
 	mtx_lock(&filterops_lock);
 	if (sysfilt_ops[~filt].for_fop == &null_filtops ||
 	    sysfilt_ops[~filt].for_fop == NULL)
 		error = EINVAL;
 	else if (sysfilt_ops[~filt].for_refcnt != 0)
 		error = EBUSY;
 	else {
 		sysfilt_ops[~filt].for_fop = &null_filtops;
 		sysfilt_ops[~filt].for_refcnt = 0;
 	}
 	mtx_unlock(&filterops_lock);
 
 	return error;
 }
 
 static struct filterops *
 kqueue_fo_find(int filt)
 {
 
 	if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
 		return NULL;
 
 	if (sysfilt_ops[~filt].for_nolock)
 		return sysfilt_ops[~filt].for_fop;
 
 	mtx_lock(&filterops_lock);
 	sysfilt_ops[~filt].for_refcnt++;
 	if (sysfilt_ops[~filt].for_fop == NULL)
 		sysfilt_ops[~filt].for_fop = &null_filtops;
 	mtx_unlock(&filterops_lock);
 
 	return sysfilt_ops[~filt].for_fop;
 }
 
 static void
 kqueue_fo_release(int filt)
 {
 
 	if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
 		return;
 
 	if (sysfilt_ops[~filt].for_nolock)
 		return;
 
 	mtx_lock(&filterops_lock);
 	KASSERT(sysfilt_ops[~filt].for_refcnt > 0,
 	    ("filter object refcount not valid on release"));
 	sysfilt_ops[~filt].for_refcnt--;
 	mtx_unlock(&filterops_lock);
 }
 
 /*
  * A ref to kq (obtained via kqueue_acquire) must be held.  waitok will
  * influence if memory allocation should wait.  Make sure it is 0 if you
  * hold any mutexes.
  */
 static int
 kqueue_register(struct kqueue *kq, struct kevent *kev, struct thread *td, int waitok)
 {
 	struct filterops *fops;
 	struct file *fp;
 	struct knote *kn, *tkn;
 	cap_rights_t rights;
 	int error, filt, event;
 	int haskqglobal, filedesc_unlock;
 
+	if ((kev->flags & (EV_ENABLE | EV_DISABLE)) == (EV_ENABLE | EV_DISABLE))
+		return (EINVAL);
+
 	fp = NULL;
 	kn = NULL;
 	error = 0;
 	haskqglobal = 0;
 	filedesc_unlock = 0;
 
 	filt = kev->filter;
 	fops = kqueue_fo_find(filt);
 	if (fops == NULL)
 		return EINVAL;
 
 	if (kev->flags & EV_ADD) {
 		/*
 		 * Prevent waiting with locks.  Non-sleepable
 		 * allocation failures are handled in the loop, only
 		 * if the spare knote appears to be actually required.
 		 */
 		tkn = knote_alloc(waitok);
 	} else {
 		tkn = NULL;
 	}
 
 findkn:
 	if (fops->f_isfd) {
 		KASSERT(td != NULL, ("td is NULL"));
 		error = fget(td, kev->ident,
 		    cap_rights_init(&rights, CAP_EVENT), &fp);
 		if (error)
 			goto done;
 
 		if ((kev->flags & EV_ADD) == EV_ADD && kqueue_expand(kq, fops,
 		    kev->ident, 0) != 0) {
 			/* try again */
 			fdrop(fp, td);
 			fp = NULL;
 			error = kqueue_expand(kq, fops, kev->ident, waitok);
 			if (error)
 				goto done;
 			goto findkn;
 		}
 
 		if (fp->f_type == DTYPE_KQUEUE) {
 			/*
 			 * If we add some intelligence about what we are doing,
 			 * we should be able to support events on ourselves.
 			 * We need to know when we are doing this to prevent
 			 * getting both the knlist lock and the kq lock since
 			 * they are the same thing.
 			 */
 			if (fp->f_data == kq) {
 				error = EINVAL;
 				goto done;
 			}
 
 			/*
 			 * Pre-lock the filedesc before the global
 			 * lock mutex, see the comment in
 			 * kqueue_close().
 			 */
 			FILEDESC_XLOCK(td->td_proc->p_fd);
 			filedesc_unlock = 1;
 			KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
 		}
 
 		KQ_LOCK(kq);
 		if (kev->ident < kq->kq_knlistsize) {
 			SLIST_FOREACH(kn, &kq->kq_knlist[kev->ident], kn_link)
 				if (kev->filter == kn->kn_filter)
 					break;
 		}
 	} else {
 		if ((kev->flags & EV_ADD) == EV_ADD)
 			kqueue_expand(kq, fops, kev->ident, waitok);
 
 		KQ_LOCK(kq);
 
 		/*
 		 * If possible, find an existing knote to use for this kevent.
 		 */
 		if (kev->filter == EVFILT_PROC &&
 		    (kev->flags & (EV_FLAG1 | EV_FLAG2)) != 0) {
 			/* This is an internal creation of a process tracking
 			 * note. Don't attempt to coalesce this with an
 			 * existing note.
 			 */
 			;			
 		} else if (kq->kq_knhashmask != 0) {
 			struct klist *list;
 
 			list = &kq->kq_knhash[
 			    KN_HASH((u_long)kev->ident, kq->kq_knhashmask)];
 			SLIST_FOREACH(kn, list, kn_link)
 				if (kev->ident == kn->kn_id &&
 				    kev->filter == kn->kn_filter)
 					break;
 		}
 	}
 
 	/* knote is in the process of changing, wait for it to stabilize. */
 	if (kn != NULL && (kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 		KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 		if (filedesc_unlock) {
 			FILEDESC_XUNLOCK(td->td_proc->p_fd);
 			filedesc_unlock = 0;
 		}
 		kq->kq_state |= KQ_FLUXWAIT;
 		msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqflxwt", 0);
 		if (fp != NULL) {
 			fdrop(fp, td);
 			fp = NULL;
 		}
 		goto findkn;
 	}
 
 	/*
 	 * kn now contains the matching knote, or NULL if no match
 	 */
 	if (kn == NULL) {
 		if (kev->flags & EV_ADD) {
 			kn = tkn;
 			tkn = NULL;
 			if (kn == NULL) {
 				KQ_UNLOCK(kq);
 				error = ENOMEM;
 				goto done;
 			}
 			kn->kn_fp = fp;
 			kn->kn_kq = kq;
 			kn->kn_fop = fops;
 			/*
 			 * apply reference counts to knote structure, and
 			 * do not release it at the end of this routine.
 			 */
 			fops = NULL;
 			fp = NULL;
 
 			kn->kn_sfflags = kev->fflags;
 			kn->kn_sdata = kev->data;
 			kev->fflags = 0;
 			kev->data = 0;
 			kn->kn_kevent = *kev;
 			kn->kn_kevent.flags &= ~(EV_ADD | EV_DELETE |
 			    EV_ENABLE | EV_DISABLE | EV_FORCEONESHOT);
 			kn->kn_status = KN_INFLUX|KN_DETACHED;
 
 			error = knote_attach(kn, kq);
 			KQ_UNLOCK(kq);
 			if (error != 0) {
 				tkn = kn;
 				goto done;
 			}
 
 			if ((error = kn->kn_fop->f_attach(kn)) != 0) {
 				knote_drop(kn, td);
 				goto done;
 			}
 			KN_LIST_LOCK(kn);
 			goto done_ev_add;
 		} else {
 			/* No matching knote and the EV_ADD flag is not set. */
 			KQ_UNLOCK(kq);
 			error = ENOENT;
 			goto done;
 		}
 	}
 	
 	if (kev->flags & EV_DELETE) {
 		kn->kn_status |= KN_INFLUX;
 		KQ_UNLOCK(kq);
 		if (!(kn->kn_status & KN_DETACHED))
 			kn->kn_fop->f_detach(kn);
 		knote_drop(kn, td);
 		goto done;
 	}
 
 	if (kev->flags & EV_FORCEONESHOT) {
 		kn->kn_flags |= EV_ONESHOT;
 		KNOTE_ACTIVATE(kn, 1);
 	}
 
 	/*
 	 * The user may change some filter values after the initial EV_ADD,
 	 * but doing so will not reset any filter which has already been
 	 * triggered.
 	 */
 	kn->kn_status |= KN_INFLUX | KN_SCAN;
 	KQ_UNLOCK(kq);
 	KN_LIST_LOCK(kn);
 	kn->kn_kevent.udata = kev->udata;
 	if (!fops->f_isfd && fops->f_touch != NULL) {
 		fops->f_touch(kn, kev, EVENT_REGISTER);
 	} else {
 		kn->kn_sfflags = kev->fflags;
 		kn->kn_sdata = kev->data;
 	}
 
 	/*
 	 * We can get here with kn->kn_knlist == NULL.  This can happen when
 	 * the initial attach event decides that the event is "completed" 
 	 * already.  i.e. filt_procattach is called on a zombie process.  It
 	 * will call filt_proc which will remove it from the list, and NULL
 	 * kn_knlist.
 	 */
 done_ev_add:
 	if ((kev->flags & EV_DISABLE) &&
 	    ((kn->kn_status & KN_DISABLED) == 0)) {
 		kn->kn_status |= KN_DISABLED;
 	}
 
 	if ((kn->kn_status & KN_DISABLED) == 0)
 		event = kn->kn_fop->f_event(kn, 0);
 	else
 		event = 0;
 	KQ_LOCK(kq);
 	if (event)
 		KNOTE_ACTIVATE(kn, 1);
 	kn->kn_status &= ~(KN_INFLUX | KN_SCAN);
 	KN_LIST_UNLOCK(kn);
 
 	if ((kev->flags & EV_ENABLE) && (kn->kn_status & KN_DISABLED)) {
 		kn->kn_status &= ~KN_DISABLED;
 		if ((kn->kn_status & KN_ACTIVE) &&
 		    ((kn->kn_status & KN_QUEUED) == 0))
 			knote_enqueue(kn);
 	}
 	KQ_UNLOCK_FLUX(kq);
 
 done:
 	KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 	if (filedesc_unlock)
 		FILEDESC_XUNLOCK(td->td_proc->p_fd);
 	if (fp != NULL)
 		fdrop(fp, td);
 	knote_free(tkn);
 	if (fops != NULL)
 		kqueue_fo_release(filt);
 	return (error);
 }
 
 static int
 kqueue_acquire(struct file *fp, struct kqueue **kqp)
 {
 	int error;
 	struct kqueue *kq;
 
 	error = 0;
 
 	kq = fp->f_data;
 	if (fp->f_type != DTYPE_KQUEUE || kq == NULL)
 		return (EBADF);
 	*kqp = kq;
 	KQ_LOCK(kq);
 	if ((kq->kq_state & KQ_CLOSING) == KQ_CLOSING) {
 		KQ_UNLOCK(kq);
 		return (EBADF);
 	}
 	kq->kq_refcnt++;
 	KQ_UNLOCK(kq);
 
 	return error;
 }
 
 static void
 kqueue_release(struct kqueue *kq, int locked)
 {
 	if (locked)
 		KQ_OWNED(kq);
 	else
 		KQ_LOCK(kq);
 	kq->kq_refcnt--;
 	if (kq->kq_refcnt == 1)
 		wakeup(&kq->kq_refcnt);
 	if (!locked)
 		KQ_UNLOCK(kq);
 }
 
 static void
 kqueue_schedtask(struct kqueue *kq)
 {
 
 	KQ_OWNED(kq);
 	KASSERT(((kq->kq_state & KQ_TASKDRAIN) != KQ_TASKDRAIN),
 	    ("scheduling kqueue task while draining"));
 
 	if ((kq->kq_state & KQ_TASKSCHED) != KQ_TASKSCHED) {
 		taskqueue_enqueue(taskqueue_kqueue, &kq->kq_task);
 		kq->kq_state |= KQ_TASKSCHED;
 	}
 }
 
 /*
  * Expand the kq to make sure we have storage for fops/ident pair.
  *
  * Return 0 on success (or no work necessary), return errno on failure.
  *
  * Not calling hashinit w/ waitok (proper malloc flag) should be safe.
  * If kqueue_register is called from a non-fd context, there usually/should
  * be no locks held.
  */
 static int
 kqueue_expand(struct kqueue *kq, struct filterops *fops, uintptr_t ident,
 	int waitok)
 {
 	struct klist *list, *tmp_knhash, *to_free;
 	u_long tmp_knhashmask;
 	int size;
 	int fd;
 	int mflag = waitok ? M_WAITOK : M_NOWAIT;
 
 	KQ_NOTOWNED(kq);
 
 	to_free = NULL;
 	if (fops->f_isfd) {
 		fd = ident;
 		if (kq->kq_knlistsize <= fd) {
 			size = kq->kq_knlistsize;
 			while (size <= fd)
 				size += KQEXTENT;
 			list = malloc(size * sizeof(*list), M_KQUEUE, mflag);
 			if (list == NULL)
 				return ENOMEM;
 			KQ_LOCK(kq);
 			if (kq->kq_knlistsize > fd) {
 				to_free = list;
 				list = NULL;
 			} else {
 				if (kq->kq_knlist != NULL) {
 					bcopy(kq->kq_knlist, list,
 					    kq->kq_knlistsize * sizeof(*list));
 					to_free = kq->kq_knlist;
 					kq->kq_knlist = NULL;
 				}
 				bzero((caddr_t)list +
 				    kq->kq_knlistsize * sizeof(*list),
 				    (size - kq->kq_knlistsize) * sizeof(*list));
 				kq->kq_knlistsize = size;
 				kq->kq_knlist = list;
 			}
 			KQ_UNLOCK(kq);
 		}
 	} else {
 		if (kq->kq_knhashmask == 0) {
 			tmp_knhash = hashinit(KN_HASHSIZE, M_KQUEUE,
 			    &tmp_knhashmask);
 			if (tmp_knhash == NULL)
 				return ENOMEM;
 			KQ_LOCK(kq);
 			if (kq->kq_knhashmask == 0) {
 				kq->kq_knhash = tmp_knhash;
 				kq->kq_knhashmask = tmp_knhashmask;
 			} else {
 				to_free = tmp_knhash;
 			}
 			KQ_UNLOCK(kq);
 		}
 	}
 	free(to_free, M_KQUEUE);
 
 	KQ_NOTOWNED(kq);
 	return 0;
 }
 
 static void
 kqueue_task(void *arg, int pending)
 {
 	struct kqueue *kq;
 	int haskqglobal;
 
 	haskqglobal = 0;
 	kq = arg;
 
 	KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
 	KQ_LOCK(kq);
 
 	KNOTE_LOCKED(&kq->kq_sel.si_note, 0);
 
 	kq->kq_state &= ~KQ_TASKSCHED;
 	if ((kq->kq_state & KQ_TASKDRAIN) == KQ_TASKDRAIN) {
 		wakeup(&kq->kq_state);
 	}
 	KQ_UNLOCK(kq);
 	KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 }
 
 /*
  * Scan, update kn_data (if not ONESHOT), and copyout triggered events.
  * We treat KN_MARKER knotes as if they are INFLUX.
  */
 static int
 kqueue_scan(struct kqueue *kq, int maxevents, struct kevent_copyops *k_ops,
     const struct timespec *tsp, struct kevent *keva, struct thread *td)
 {
 	struct kevent *kevp;
 	struct knote *kn, *marker;
 	sbintime_t asbt, rsbt;
 	int count, error, haskqglobal, influx, nkev, touch;
 
 	count = maxevents;
 	nkev = 0;
 	error = 0;
 	haskqglobal = 0;
 
 	if (maxevents == 0)
 		goto done_nl;
 
 	rsbt = 0;
 	if (tsp != NULL) {
 		if (tsp->tv_sec < 0 || tsp->tv_nsec < 0 ||
 		    tsp->tv_nsec >= 1000000000) {
 			error = EINVAL;
 			goto done_nl;
 		}
 		if (timespecisset(tsp)) {
 			if (tsp->tv_sec <= INT32_MAX) {
 				rsbt = tstosbt(*tsp);
 				if (TIMESEL(&asbt, rsbt))
 					asbt += tc_tick_sbt;
 				if (asbt <= SBT_MAX - rsbt)
 					asbt += rsbt;
 				else
 					asbt = 0;
 				rsbt >>= tc_precexp;
 			} else
 				asbt = 0;
 		} else
 			asbt = -1;
 	} else
 		asbt = 0;
 	marker = knote_alloc(1);
 	marker->kn_status = KN_MARKER;
 	KQ_LOCK(kq);
 
 retry:
 	kevp = keva;
 	if (kq->kq_count == 0) {
 		if (asbt == -1) {
 			error = EWOULDBLOCK;
 		} else {
 			kq->kq_state |= KQ_SLEEP;
 			error = msleep_sbt(kq, &kq->kq_lock, PSOCK | PCATCH,
 			    "kqread", asbt, rsbt, C_ABSOLUTE);
 		}
 		if (error == 0)
 			goto retry;
 		/* don't restart after signals... */
 		if (error == ERESTART)
 			error = EINTR;
 		else if (error == EWOULDBLOCK)
 			error = 0;
 		goto done;
 	}
 
 	TAILQ_INSERT_TAIL(&kq->kq_head, marker, kn_tqe);
 	influx = 0;
 	while (count) {
 		KQ_OWNED(kq);
 		kn = TAILQ_FIRST(&kq->kq_head);
 
 		if ((kn->kn_status == KN_MARKER && kn != marker) ||
 		    (kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 			if (influx) {
 				influx = 0;
 				KQ_FLUX_WAKEUP(kq);
 			}
 			kq->kq_state |= KQ_FLUXWAIT;
 			error = msleep(kq, &kq->kq_lock, PSOCK,
 			    "kqflxwt", 0);
 			continue;
 		}
 
 		TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
 		if ((kn->kn_status & KN_DISABLED) == KN_DISABLED) {
 			kn->kn_status &= ~KN_QUEUED;
 			kq->kq_count--;
 			continue;
 		}
 		if (kn == marker) {
 			KQ_FLUX_WAKEUP(kq);
 			if (count == maxevents)
 				goto retry;
 			goto done;
 		}
 		KASSERT((kn->kn_status & KN_INFLUX) == 0,
 		    ("KN_INFLUX set when not suppose to be"));
 
 		if ((kn->kn_flags & EV_DROP) == EV_DROP) {
 			kn->kn_status &= ~KN_QUEUED;
 			kn->kn_status |= KN_INFLUX;
 			kq->kq_count--;
 			KQ_UNLOCK(kq);
 			/*
 			 * We don't need to lock the list since we've marked
 			 * it _INFLUX.
 			 */
 			if (!(kn->kn_status & KN_DETACHED))
 				kn->kn_fop->f_detach(kn);
 			knote_drop(kn, td);
 			KQ_LOCK(kq);
 			continue;
 		} else if ((kn->kn_flags & EV_ONESHOT) == EV_ONESHOT) {
 			kn->kn_status &= ~KN_QUEUED;
 			kn->kn_status |= KN_INFLUX;
 			kq->kq_count--;
 			KQ_UNLOCK(kq);
 			/*
 			 * We don't need to lock the list since we've marked
 			 * it _INFLUX.
 			 */
 			*kevp = kn->kn_kevent;
 			if (!(kn->kn_status & KN_DETACHED))
 				kn->kn_fop->f_detach(kn);
 			knote_drop(kn, td);
 			KQ_LOCK(kq);
 			kn = NULL;
 		} else {
 			kn->kn_status |= KN_INFLUX | KN_SCAN;
 			KQ_UNLOCK(kq);
 			if ((kn->kn_status & KN_KQUEUE) == KN_KQUEUE)
 				KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
 			KN_LIST_LOCK(kn);
 			if (kn->kn_fop->f_event(kn, 0) == 0) {
 				KQ_LOCK(kq);
 				KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 				kn->kn_status &=
 				    ~(KN_QUEUED | KN_ACTIVE | KN_INFLUX |
 				    KN_SCAN);
 				kq->kq_count--;
 				KN_LIST_UNLOCK(kn);
 				influx = 1;
 				continue;
 			}
 			touch = (!kn->kn_fop->f_isfd &&
 			    kn->kn_fop->f_touch != NULL);
 			if (touch)
 				kn->kn_fop->f_touch(kn, kevp, EVENT_PROCESS);
 			else
 				*kevp = kn->kn_kevent;
 			KQ_LOCK(kq);
 			KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 			if (kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) {
 				/* 
 				 * Manually clear knotes who weren't 
 				 * 'touch'ed.
 				 */
 				if (touch == 0 && kn->kn_flags & EV_CLEAR) {
 					kn->kn_data = 0;
 					kn->kn_fflags = 0;
 				}
 				if (kn->kn_flags & EV_DISPATCH)
 					kn->kn_status |= KN_DISABLED;
 				kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
 				kq->kq_count--;
 			} else
 				TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
 			
 			kn->kn_status &= ~(KN_INFLUX | KN_SCAN);
 			KN_LIST_UNLOCK(kn);
 			influx = 1;
 		}
 
 		/* we are returning a copy to the user */
 		kevp++;
 		nkev++;
 		count--;
 
 		if (nkev == KQ_NEVENTS) {
 			influx = 0;
 			KQ_UNLOCK_FLUX(kq);
 			error = k_ops->k_copyout(k_ops->arg, keva, nkev);
 			nkev = 0;
 			kevp = keva;
 			KQ_LOCK(kq);
 			if (error)
 				break;
 		}
 	}
 	TAILQ_REMOVE(&kq->kq_head, marker, kn_tqe);
 done:
 	KQ_OWNED(kq);
 	KQ_UNLOCK_FLUX(kq);
 	knote_free(marker);
 done_nl:
 	KQ_NOTOWNED(kq);
 	if (nkev != 0)
 		error = k_ops->k_copyout(k_ops->arg, keva, nkev);
 	td->td_retval[0] = maxevents - count;
 	return (error);
 }
 
 /*ARGSUSED*/
 static int
 kqueue_ioctl(struct file *fp, u_long cmd, void *data,
 	struct ucred *active_cred, struct thread *td)
 {
 	/*
 	 * Enabling sigio causes two major problems:
 	 * 1) infinite recursion:
 	 * Synopsys: kevent is being used to track signals and have FIOASYNC
 	 * set.  On receipt of a signal this will cause a kqueue to recurse
 	 * into itself over and over.  Sending the sigio causes the kqueue
 	 * to become ready, which in turn posts sigio again, forever.
 	 * Solution: this can be solved by setting a flag in the kqueue that
 	 * we have a SIGIO in progress.
 	 * 2) locking problems:
 	 * Synopsys: Kqueue is a leaf subsystem, but adding signalling puts
 	 * us above the proc and pgrp locks.
 	 * Solution: Post a signal using an async mechanism, being sure to
 	 * record a generation count in the delivery so that we do not deliver
 	 * a signal to the wrong process.
 	 *
 	 * Note, these two mechanisms are somewhat mutually exclusive!
 	 */
 #if 0
 	struct kqueue *kq;
 
 	kq = fp->f_data;
 	switch (cmd) {
 	case FIOASYNC:
 		if (*(int *)data) {
 			kq->kq_state |= KQ_ASYNC;
 		} else {
 			kq->kq_state &= ~KQ_ASYNC;
 		}
 		return (0);
 
 	case FIOSETOWN:
 		return (fsetown(*(int *)data, &kq->kq_sigio));
 
 	case FIOGETOWN:
 		*(int *)data = fgetown(&kq->kq_sigio);
 		return (0);
 	}
 #endif
 
 	return (ENOTTY);
 }
 
 /*ARGSUSED*/
 static int
 kqueue_poll(struct file *fp, int events, struct ucred *active_cred,
 	struct thread *td)
 {
 	struct kqueue *kq;
 	int revents = 0;
 	int error;
 
 	if ((error = kqueue_acquire(fp, &kq)))
 		return POLLERR;
 
 	KQ_LOCK(kq);
 	if (events & (POLLIN | POLLRDNORM)) {
 		if (kq->kq_count) {
 			revents |= events & (POLLIN | POLLRDNORM);
 		} else {
 			selrecord(td, &kq->kq_sel);
 			if (SEL_WAITING(&kq->kq_sel))
 				kq->kq_state |= KQ_SEL;
 		}
 	}
 	kqueue_release(kq, 1);
 	KQ_UNLOCK(kq);
 	return (revents);
 }
 
 /*ARGSUSED*/
 static int
 kqueue_stat(struct file *fp, struct stat *st, struct ucred *active_cred,
 	struct thread *td)
 {
 
 	bzero((void *)st, sizeof *st);
 	/*
 	 * We no longer return kq_count because the unlocked value is useless.
 	 * If you spent all this time getting the count, why not spend your
 	 * syscall better by calling kevent?
 	 *
 	 * XXX - This is needed for libc_r.
 	 */
 	st->st_mode = S_IFIFO;
 	return (0);
 }
 
 static void
 kqueue_drain(struct kqueue *kq, struct thread *td)
 {
 	struct knote *kn;
 	int i;
 
 	KQ_LOCK(kq);
 
 	KASSERT((kq->kq_state & KQ_CLOSING) != KQ_CLOSING,
 	    ("kqueue already closing"));
 	kq->kq_state |= KQ_CLOSING;
 	if (kq->kq_refcnt > 1)
 		msleep(&kq->kq_refcnt, &kq->kq_lock, PSOCK, "kqclose", 0);
 
 	KASSERT(kq->kq_refcnt == 1, ("other refs are out there!"));
 
 	KASSERT(knlist_empty(&kq->kq_sel.si_note),
 	    ("kqueue's knlist not empty"));
 
 	for (i = 0; i < kq->kq_knlistsize; i++) {
 		while ((kn = SLIST_FIRST(&kq->kq_knlist[i])) != NULL) {
 			if ((kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 				kq->kq_state |= KQ_FLUXWAIT;
 				msleep(kq, &kq->kq_lock, PSOCK, "kqclo1", 0);
 				continue;
 			}
 			kn->kn_status |= KN_INFLUX;
 			KQ_UNLOCK(kq);
 			if (!(kn->kn_status & KN_DETACHED))
 				kn->kn_fop->f_detach(kn);
 			knote_drop(kn, td);
 			KQ_LOCK(kq);
 		}
 	}
 	if (kq->kq_knhashmask != 0) {
 		for (i = 0; i <= kq->kq_knhashmask; i++) {
 			while ((kn = SLIST_FIRST(&kq->kq_knhash[i])) != NULL) {
 				if ((kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 					kq->kq_state |= KQ_FLUXWAIT;
 					msleep(kq, &kq->kq_lock, PSOCK,
 					       "kqclo2", 0);
 					continue;
 				}
 				kn->kn_status |= KN_INFLUX;
 				KQ_UNLOCK(kq);
 				if (!(kn->kn_status & KN_DETACHED))
 					kn->kn_fop->f_detach(kn);
 				knote_drop(kn, td);
 				KQ_LOCK(kq);
 			}
 		}
 	}
 
 	if ((kq->kq_state & KQ_TASKSCHED) == KQ_TASKSCHED) {
 		kq->kq_state |= KQ_TASKDRAIN;
 		msleep(&kq->kq_state, &kq->kq_lock, PSOCK, "kqtqdr", 0);
 	}
 
 	if ((kq->kq_state & KQ_SEL) == KQ_SEL) {
 		selwakeuppri(&kq->kq_sel, PSOCK);
 		if (!SEL_WAITING(&kq->kq_sel))
 			kq->kq_state &= ~KQ_SEL;
 	}
 
 	KQ_UNLOCK(kq);
 }
 
 static void
 kqueue_destroy(struct kqueue *kq)
 {
 
 	KASSERT(kq->kq_fdp == NULL,
 	    ("kqueue still attached to a file descriptor"));
 	seldrain(&kq->kq_sel);
 	knlist_destroy(&kq->kq_sel.si_note);
 	mtx_destroy(&kq->kq_lock);
 
 	if (kq->kq_knhash != NULL)
 		free(kq->kq_knhash, M_KQUEUE);
 	if (kq->kq_knlist != NULL)
 		free(kq->kq_knlist, M_KQUEUE);
 
 	funsetown(&kq->kq_sigio);
 }
 
 /*ARGSUSED*/
 static int
 kqueue_close(struct file *fp, struct thread *td)
 {
 	struct kqueue *kq = fp->f_data;
 	struct filedesc *fdp;
 	int error;
 	int filedesc_unlock;
 
 	if ((error = kqueue_acquire(fp, &kq)))
 		return error;
 	kqueue_drain(kq, td);
 
 	/*
 	 * We could be called due to the knote_drop() doing fdrop(),
 	 * called from kqueue_register().  In this case the global
 	 * lock is owned, and filedesc sx is locked before, to not
 	 * take the sleepable lock after non-sleepable.
 	 */
 	fdp = kq->kq_fdp;
 	kq->kq_fdp = NULL;
 	if (!sx_xlocked(FILEDESC_LOCK(fdp))) {
 		FILEDESC_XLOCK(fdp);
 		filedesc_unlock = 1;
 	} else
 		filedesc_unlock = 0;
 	TAILQ_REMOVE(&fdp->fd_kqlist, kq, kq_list);
 	if (filedesc_unlock)
 		FILEDESC_XUNLOCK(fdp);
 
 	kqueue_destroy(kq);
 	chgkqcnt(kq->kq_cred->cr_ruidinfo, -1, 0);
 	crfree(kq->kq_cred);
 	free(kq, M_KQUEUE);
 	fp->f_data = NULL;
 
 	return (0);
 }
 
 static int
 kqueue_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
 {
 
 	kif->kf_type = KF_TYPE_KQUEUE;
 	return (0);
 }
 
 static void
 kqueue_wakeup(struct kqueue *kq)
 {
 	KQ_OWNED(kq);
 
 	if ((kq->kq_state & KQ_SLEEP) == KQ_SLEEP) {
 		kq->kq_state &= ~KQ_SLEEP;
 		wakeup(kq);
 	}
 	if ((kq->kq_state & KQ_SEL) == KQ_SEL) {
 		selwakeuppri(&kq->kq_sel, PSOCK);
 		if (!SEL_WAITING(&kq->kq_sel))
 			kq->kq_state &= ~KQ_SEL;
 	}
 	if (!knlist_empty(&kq->kq_sel.si_note))
 		kqueue_schedtask(kq);
 	if ((kq->kq_state & KQ_ASYNC) == KQ_ASYNC) {
 		pgsigio(&kq->kq_sigio, SIGIO, 0);
 	}
 }
 
 /*
  * Walk down a list of knotes, activating them if their event has triggered.
  *
  * There is a possibility to optimize in the case of one kq watching another.
  * Instead of scheduling a task to wake it up, you could pass enough state
  * down the chain to make up the parent kqueue.  Make this code functional
  * first.
  */
 void
 knote(struct knlist *list, long hint, int lockflags)
 {
 	struct kqueue *kq;
 	struct knote *kn, *tkn;
 	int error;
 
 	if (list == NULL)
 		return;
 
 	KNL_ASSERT_LOCK(list, lockflags & KNF_LISTLOCKED);
 
 	if ((lockflags & KNF_LISTLOCKED) == 0)
 		list->kl_lock(list->kl_lockarg); 
 
 	/*
 	 * If we unlock the list lock (and set KN_INFLUX), we can
 	 * eliminate the kqueue scheduling, but this will introduce
 	 * four lock/unlock's for each knote to test.  Also, marker
 	 * would be needed to keep iteration position, since filters
 	 * or other threads could remove events.
 	 */
 	SLIST_FOREACH_SAFE(kn, &list->kl_list, kn_selnext, tkn) {
 		kq = kn->kn_kq;
 		KQ_LOCK(kq);
 		if ((kn->kn_status & (KN_INFLUX | KN_SCAN)) == KN_INFLUX) {
 			/*
 			 * Do not process the influx notes, except for
 			 * the influx coming from the kq unlock in the
 			 * kqueue_scan().  In the later case, we do
 			 * not interfere with the scan, since the code
 			 * fragment in kqueue_scan() locks the knlist,
 			 * and cannot proceed until we finished.
 			 */
 			KQ_UNLOCK(kq);
 		} else if ((lockflags & KNF_NOKQLOCK) != 0) {
 			kn->kn_status |= KN_INFLUX;
 			KQ_UNLOCK(kq);
 			error = kn->kn_fop->f_event(kn, hint);
 			KQ_LOCK(kq);
 			kn->kn_status &= ~KN_INFLUX;
 			if (error)
 				KNOTE_ACTIVATE(kn, 1);
 			KQ_UNLOCK_FLUX(kq);
 		} else {
 			kn->kn_status |= KN_HASKQLOCK;
 			if (kn->kn_fop->f_event(kn, hint))
 				KNOTE_ACTIVATE(kn, 1);
 			kn->kn_status &= ~KN_HASKQLOCK;
 			KQ_UNLOCK(kq);
 		}
 	}
 	if ((lockflags & KNF_LISTLOCKED) == 0)
 		list->kl_unlock(list->kl_lockarg); 
 }
 
 /*
  * add a knote to a knlist
  */
 void
 knlist_add(struct knlist *knl, struct knote *kn, int islocked)
 {
 	KNL_ASSERT_LOCK(knl, islocked);
 	KQ_NOTOWNED(kn->kn_kq);
 	KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) ==
 	    (KN_INFLUX|KN_DETACHED), ("knote not KN_INFLUX and KN_DETACHED"));
 	if (!islocked)
 		knl->kl_lock(knl->kl_lockarg);
 	SLIST_INSERT_HEAD(&knl->kl_list, kn, kn_selnext);
 	if (!islocked)
 		knl->kl_unlock(knl->kl_lockarg);
 	KQ_LOCK(kn->kn_kq);
 	kn->kn_knlist = knl;
 	kn->kn_status &= ~KN_DETACHED;
 	KQ_UNLOCK(kn->kn_kq);
 }
 
 static void
 knlist_remove_kq(struct knlist *knl, struct knote *kn, int knlislocked, int kqislocked)
 {
 	KASSERT(!(!!kqislocked && !knlislocked), ("kq locked w/o knl locked"));
 	KNL_ASSERT_LOCK(knl, knlislocked);
 	mtx_assert(&kn->kn_kq->kq_lock, kqislocked ? MA_OWNED : MA_NOTOWNED);
 	if (!kqislocked)
 		KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) == KN_INFLUX,
     ("knlist_remove called w/o knote being KN_INFLUX or already removed"));
 	if (!knlislocked)
 		knl->kl_lock(knl->kl_lockarg);
 	SLIST_REMOVE(&knl->kl_list, kn, knote, kn_selnext);
 	kn->kn_knlist = NULL;
 	if (!knlislocked)
 		knl->kl_unlock(knl->kl_lockarg);
 	if (!kqislocked)
 		KQ_LOCK(kn->kn_kq);
 	kn->kn_status |= KN_DETACHED;
 	if (!kqislocked)
 		KQ_UNLOCK(kn->kn_kq);
 }
 
 /*
  * remove knote from the specified knlist
  */
 void
 knlist_remove(struct knlist *knl, struct knote *kn, int islocked)
 {
 
 	knlist_remove_kq(knl, kn, islocked, 0);
 }
 
 /*
  * remove knote from the specified knlist while in f_event handler.
  */
 void
 knlist_remove_inevent(struct knlist *knl, struct knote *kn)
 {
 
 	knlist_remove_kq(knl, kn, 1,
 	    (kn->kn_status & KN_HASKQLOCK) == KN_HASKQLOCK);
 }
 
 int
 knlist_empty(struct knlist *knl)
 {
 
 	KNL_ASSERT_LOCKED(knl);
 	return SLIST_EMPTY(&knl->kl_list);
 }
 
 static struct mtx	knlist_lock;
 MTX_SYSINIT(knlist_lock, &knlist_lock, "knlist lock for lockless objects",
 	MTX_DEF);
 static void knlist_mtx_lock(void *arg);
 static void knlist_mtx_unlock(void *arg);
 
 static void
 knlist_mtx_lock(void *arg)
 {
 
 	mtx_lock((struct mtx *)arg);
 }
 
 static void
 knlist_mtx_unlock(void *arg)
 {
 
 	mtx_unlock((struct mtx *)arg);
 }
 
 static void
 knlist_mtx_assert_locked(void *arg)
 {
 
 	mtx_assert((struct mtx *)arg, MA_OWNED);
 }
 
 static void
 knlist_mtx_assert_unlocked(void *arg)
 {
 
 	mtx_assert((struct mtx *)arg, MA_NOTOWNED);
 }
 
 static void
 knlist_rw_rlock(void *arg)
 {
 
 	rw_rlock((struct rwlock *)arg);
 }
 
 static void
 knlist_rw_runlock(void *arg)
 {
 
 	rw_runlock((struct rwlock *)arg);
 }
 
 static void
 knlist_rw_assert_locked(void *arg)
 {
 
 	rw_assert((struct rwlock *)arg, RA_LOCKED);
 }
 
 static void
 knlist_rw_assert_unlocked(void *arg)
 {
 
 	rw_assert((struct rwlock *)arg, RA_UNLOCKED);
 }
 
 void
 knlist_init(struct knlist *knl, void *lock, void (*kl_lock)(void *),
     void (*kl_unlock)(void *),
     void (*kl_assert_locked)(void *), void (*kl_assert_unlocked)(void *))
 {
 
 	if (lock == NULL)
 		knl->kl_lockarg = &knlist_lock;
 	else
 		knl->kl_lockarg = lock;
 
 	if (kl_lock == NULL)
 		knl->kl_lock = knlist_mtx_lock;
 	else
 		knl->kl_lock = kl_lock;
 	if (kl_unlock == NULL)
 		knl->kl_unlock = knlist_mtx_unlock;
 	else
 		knl->kl_unlock = kl_unlock;
 	if (kl_assert_locked == NULL)
 		knl->kl_assert_locked = knlist_mtx_assert_locked;
 	else
 		knl->kl_assert_locked = kl_assert_locked;
 	if (kl_assert_unlocked == NULL)
 		knl->kl_assert_unlocked = knlist_mtx_assert_unlocked;
 	else
 		knl->kl_assert_unlocked = kl_assert_unlocked;
 
 	SLIST_INIT(&knl->kl_list);
 }
 
 void
 knlist_init_mtx(struct knlist *knl, struct mtx *lock)
 {
 
 	knlist_init(knl, lock, NULL, NULL, NULL, NULL);
 }
 
 void
 knlist_init_rw_reader(struct knlist *knl, struct rwlock *lock)
 {
 
 	knlist_init(knl, lock, knlist_rw_rlock, knlist_rw_runlock,
 	    knlist_rw_assert_locked, knlist_rw_assert_unlocked);
 }
 
 void
 knlist_destroy(struct knlist *knl)
 {
 
 #ifdef INVARIANTS
 	/*
 	 * if we run across this error, we need to find the offending
 	 * driver and have it call knlist_clear or knlist_delete.
 	 */
 	if (!SLIST_EMPTY(&knl->kl_list))
 		printf("WARNING: destroying knlist w/ knotes on it!\n");
 #endif
 
 	knl->kl_lockarg = knl->kl_lock = knl->kl_unlock = NULL;
 	SLIST_INIT(&knl->kl_list);
 }
 
 /*
  * Even if we are locked, we may need to drop the lock to allow any influx
  * knotes time to "settle".
  */
 void
 knlist_cleardel(struct knlist *knl, struct thread *td, int islocked, int killkn)
 {
 	struct knote *kn, *kn2;
 	struct kqueue *kq;
 
 	if (islocked)
 		KNL_ASSERT_LOCKED(knl);
 	else {
 		KNL_ASSERT_UNLOCKED(knl);
 again:		/* need to reacquire lock since we have dropped it */
 		knl->kl_lock(knl->kl_lockarg);
 	}
 
 	SLIST_FOREACH_SAFE(kn, &knl->kl_list, kn_selnext, kn2) {
 		kq = kn->kn_kq;
 		KQ_LOCK(kq);
 		if ((kn->kn_status & KN_INFLUX)) {
 			KQ_UNLOCK(kq);
 			continue;
 		}
 		knlist_remove_kq(knl, kn, 1, 1);
 		if (killkn) {
 			kn->kn_status |= KN_INFLUX | KN_DETACHED;
 			KQ_UNLOCK(kq);
 			knote_drop(kn, td);
 		} else {
 			/* Make sure cleared knotes disappear soon */
 			kn->kn_flags |= (EV_EOF | EV_ONESHOT);
 			KQ_UNLOCK(kq);
 		}
 		kq = NULL;
 	}
 
 	if (!SLIST_EMPTY(&knl->kl_list)) {
 		/* there are still KN_INFLUX remaining */
 		kn = SLIST_FIRST(&knl->kl_list);
 		kq = kn->kn_kq;
 		KQ_LOCK(kq);
 		KASSERT(kn->kn_status & KN_INFLUX,
 		    ("knote removed w/o list lock"));
 		knl->kl_unlock(knl->kl_lockarg);
 		kq->kq_state |= KQ_FLUXWAIT;
 		msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqkclr", 0);
 		kq = NULL;
 		goto again;
 	}
 
 	if (islocked)
 		KNL_ASSERT_LOCKED(knl);
 	else {
 		knl->kl_unlock(knl->kl_lockarg);
 		KNL_ASSERT_UNLOCKED(knl);
 	}
 }
 
 /*
  * Remove all knotes referencing a specified fd must be called with FILEDESC
  * lock.  This prevents a race where a new fd comes along and occupies the
  * entry and we attach a knote to the fd.
  */
 void
 knote_fdclose(struct thread *td, int fd)
 {
 	struct filedesc *fdp = td->td_proc->p_fd;
 	struct kqueue *kq;
 	struct knote *kn;
 	int influx;
 
 	FILEDESC_XLOCK_ASSERT(fdp);
 
 	/*
 	 * We shouldn't have to worry about new kevents appearing on fd
 	 * since filedesc is locked.
 	 */
 	TAILQ_FOREACH(kq, &fdp->fd_kqlist, kq_list) {
 		KQ_LOCK(kq);
 
 again:
 		influx = 0;
 		while (kq->kq_knlistsize > fd &&
 		    (kn = SLIST_FIRST(&kq->kq_knlist[fd])) != NULL) {
 			if (kn->kn_status & KN_INFLUX) {
 				/* someone else might be waiting on our knote */
 				if (influx)
 					wakeup(kq);
 				kq->kq_state |= KQ_FLUXWAIT;
 				msleep(kq, &kq->kq_lock, PSOCK, "kqflxwt", 0);
 				goto again;
 			}
 			kn->kn_status |= KN_INFLUX;
 			KQ_UNLOCK(kq);
 			if (!(kn->kn_status & KN_DETACHED))
 				kn->kn_fop->f_detach(kn);
 			knote_drop(kn, td);
 			influx = 1;
 			KQ_LOCK(kq);
 		}
 		KQ_UNLOCK_FLUX(kq);
 	}
 }
 
 static int
 knote_attach(struct knote *kn, struct kqueue *kq)
 {
 	struct klist *list;
 
 	KASSERT(kn->kn_status & KN_INFLUX, ("knote not marked INFLUX"));
 	KQ_OWNED(kq);
 
 	if (kn->kn_fop->f_isfd) {
 		if (kn->kn_id >= kq->kq_knlistsize)
 			return ENOMEM;
 		list = &kq->kq_knlist[kn->kn_id];
 	} else {
 		if (kq->kq_knhash == NULL)
 			return ENOMEM;
 		list = &kq->kq_knhash[KN_HASH(kn->kn_id, kq->kq_knhashmask)];
 	}
 
 	SLIST_INSERT_HEAD(list, kn, kn_link);
 
 	return 0;
 }
 
 /*
  * knote must already have been detached using the f_detach method.
  * no lock need to be held, it is assumed that the KN_INFLUX flag is set
  * to prevent other removal.
  */
 static void
 knote_drop(struct knote *kn, struct thread *td)
 {
 	struct kqueue *kq;
 	struct klist *list;
 
 	kq = kn->kn_kq;
 
 	KQ_NOTOWNED(kq);
 	KASSERT((kn->kn_status & KN_INFLUX) == KN_INFLUX,
 	    ("knote_drop called without KN_INFLUX set in kn_status"));
 
 	KQ_LOCK(kq);
 	if (kn->kn_fop->f_isfd)
 		list = &kq->kq_knlist[kn->kn_id];
 	else
 		list = &kq->kq_knhash[KN_HASH(kn->kn_id, kq->kq_knhashmask)];
 
 	if (!SLIST_EMPTY(list))
 		SLIST_REMOVE(list, kn, knote, kn_link);
 	if (kn->kn_status & KN_QUEUED)
 		knote_dequeue(kn);
 	KQ_UNLOCK_FLUX(kq);
 
 	if (kn->kn_fop->f_isfd) {
 		fdrop(kn->kn_fp, td);
 		kn->kn_fp = NULL;
 	}
 	kqueue_fo_release(kn->kn_kevent.filter);
 	kn->kn_fop = NULL;
 	knote_free(kn);
 }
 
 static void
 knote_enqueue(struct knote *kn)
 {
 	struct kqueue *kq = kn->kn_kq;
 
 	KQ_OWNED(kn->kn_kq);
 	KASSERT((kn->kn_status & KN_QUEUED) == 0, ("knote already queued"));
 
 	TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
 	kn->kn_status |= KN_QUEUED;
 	kq->kq_count++;
 	kqueue_wakeup(kq);
 }
 
 static void
 knote_dequeue(struct knote *kn)
 {
 	struct kqueue *kq = kn->kn_kq;
 
 	KQ_OWNED(kn->kn_kq);
 	KASSERT(kn->kn_status & KN_QUEUED, ("knote not queued"));
 
 	TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
 	kn->kn_status &= ~KN_QUEUED;
 	kq->kq_count--;
 }
 
 static void
 knote_init(void)
 {
 
 	knote_zone = uma_zcreate("KNOTE", sizeof(struct knote), NULL, NULL,
 	    NULL, NULL, UMA_ALIGN_PTR, 0);
 }
 SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_ANY, knote_init, NULL);
 
 static struct knote *
 knote_alloc(int waitok)
 {
 
 	return (uma_zalloc(knote_zone, (waitok ? M_WAITOK : M_NOWAIT) |
 	    M_ZERO));
 }
 
 static void
 knote_free(struct knote *kn)
 {
 
 	uma_zfree(knote_zone, kn);
 }
 
 /*
  * Register the kev w/ the kq specified by fd.
  */
 int 
 kqfd_register(int fd, struct kevent *kev, struct thread *td, int waitok)
 {
 	struct kqueue *kq;
 	struct file *fp;
 	cap_rights_t rights;
 	int error;
 
 	error = fget(td, fd, cap_rights_init(&rights, CAP_KQUEUE_CHANGE), &fp);
 	if (error != 0)
 		return (error);
 	if ((error = kqueue_acquire(fp, &kq)) != 0)
 		goto noacquire;
 
 	error = kqueue_register(kq, kev, td, waitok);
 
 	kqueue_release(kq, 0);
 
 noacquire:
 	fdrop(fp, td);
 
 	return error;
 }