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

/*
 * Copyright (c) 2000-2008 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/malloc.h> 
#include <sys/unistd.h>
#include <sys/file_internal.h>
#include <sys/fcntl.h>
#include <sys/select.h>
#include <sys/queue.h>
#include <sys/event.h>
#include <sys/eventvar.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/uio.h>
#include <sys/sysproto.h>
#include <sys/user.h>
#include <sys/vnode_internal.h>
#include <string.h>
#include <sys/proc_info.h>

#include <kern/lock.h>
#include <kern/clock.h>
#include <kern/thread_call.h>
#include <kern/sched_prim.h>
#include <kern/zalloc.h>
#include <kern/assert.h>

#include <libkern/libkern.h>
#include "net/net_str_id.h"

#include <mach/task.h>
#include <kern/vm_pressure.h>

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

#define KQ_EVENT NULL

static inline void kqlock(struct kqueue *kq);
static inline void kqunlock(struct kqueue *kq);

static int      kqlock2knoteuse(struct kqueue *kq, struct knote *kn);
static int      kqlock2knoteusewait(struct kqueue *kq, struct knote *kn);
static int      kqlock2knotedrop(struct kqueue *kq, struct knote *kn);
static int      knoteuse2kqlock(struct kqueue *kq, struct knote *kn);

static void     kqueue_wakeup(struct kqueue *kq, int closed);
static int      kqueue_read(struct fileproc *fp, struct uio *uio,
                    int flags, vfs_context_t ctx);
static int      kqueue_write(struct fileproc *fp, struct uio *uio,
                    int flags, vfs_context_t ctx);
static int      kqueue_ioctl(struct fileproc *fp, u_long com, caddr_t data,
                    vfs_context_t ctx);
static int      kqueue_select(struct fileproc *fp, int which, void *wql, 
                    vfs_context_t ctx);
static int      kqueue_close(struct fileglob *fg, vfs_context_t ctx);
static int      kqueue_kqfilter(struct fileproc *fp, struct knote *kn, vfs_context_t ctx);
static int      kqueue_drain(struct fileproc *fp, vfs_context_t ctx);
extern int      kqueue_stat(struct fileproc *fp, void  *ub, int isstat64, vfs_context_t ctx);

static struct fileops kqueueops = {
        .fo_read = kqueue_read,
        .fo_write = kqueue_write,
        .fo_ioctl = kqueue_ioctl,
        .fo_select = kqueue_select,
        .fo_close = kqueue_close,
        .fo_kqfilter = kqueue_kqfilter,
        .fo_drain = kqueue_drain,
};

static int kevent_internal(struct proc *p, int iskev64, user_addr_t changelist,
                int nchanges, user_addr_t eventlist, int nevents, int fd, 
                user_addr_t utimeout, unsigned int flags, int32_t *retval);
static int kevent_copyin(user_addr_t *addrp, struct kevent64_s *kevp, struct proc *p, int iskev64);
static int kevent_copyout(struct kevent64_s *kevp, user_addr_t *addrp, struct proc *p, int iskev64);
char * kevent_description(struct kevent64_s *kevp, char *s, size_t n);

static int      kevent_callback(struct kqueue *kq, struct kevent64_s *kevp, void *data);
static void     kevent_continue(struct kqueue *kq, void *data, int error);
static void     kqueue_scan_continue(void *contp, wait_result_t wait_result);
static int      kqueue_process(struct kqueue *kq, kevent_callback_t callback,
                               void *data, int *countp, struct proc *p);
static int      kqueue_begin_processing(struct kqueue *kq);
static void     kqueue_end_processing(struct kqueue *kq);
static int      knote_process(struct knote *kn, kevent_callback_t callback,
                              void *data, struct kqtailq *inprocessp, struct proc *p);
static void     knote_put(struct knote *kn);
static int      knote_fdpattach(struct knote *kn, struct filedesc *fdp, struct proc *p);
static void     knote_drop(struct knote *kn, struct proc *p);
static void     knote_activate(struct knote *kn, int);
static void     knote_deactivate(struct knote *kn);
static void     knote_enqueue(struct knote *kn);
static void     knote_dequeue(struct knote *kn);
static struct   knote *knote_alloc(void);
static void     knote_free(struct knote *kn);

static int      filt_fileattach(struct knote *kn);
static struct filterops file_filtops = {
        .f_isfd = 1,
        .f_attach = filt_fileattach,
};

static void     filt_kqdetach(struct knote *kn);
static int      filt_kqueue(struct knote *kn, long hint);
static struct filterops kqread_filtops = {
        .f_isfd = 1,
        .f_detach = filt_kqdetach,
        .f_event = filt_kqueue,
};

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

static int      filt_procattach(struct knote *kn);
static void     filt_procdetach(struct knote *kn);
static int      filt_proc(struct knote *kn, long hint);
static struct filterops proc_filtops = {
        .f_attach = filt_procattach,
        .f_detach = filt_procdetach,
        .f_event = filt_proc,
};

static int filt_vmattach(struct knote *kn);
static void filt_vmdetach(struct knote *kn);
static int filt_vm(struct knote *kn, long hint);
static struct filterops vm_filtops = {
        .f_attach = filt_vmattach,
        .f_detach = filt_vmdetach,
        .f_event = filt_vm,
};

extern struct filterops fs_filtops;

extern struct filterops sig_filtops;

/* Timer filter */
static int      filt_timerattach(struct knote *kn);
static void     filt_timerdetach(struct knote *kn);
static int      filt_timer(struct knote *kn, long hint);
static void     filt_timertouch(struct knote *kn, struct kevent64_s *kev, 
                long type);
static struct filterops timer_filtops = {
        .f_attach = filt_timerattach,
        .f_detach = filt_timerdetach,
        .f_event = filt_timer,
        .f_touch = filt_timertouch,
};

/* Helpers */

static void     filt_timerexpire(void *knx, void *param1);
static int      filt_timervalidate(struct knote *kn);
static void     filt_timerupdate(struct knote *kn);
static void     filt_timercancel(struct knote *kn);

#define TIMER_RUNNING           0x1
#define TIMER_CANCELWAIT        0x2

static lck_mtx_t _filt_timerlock;
static void     filt_timerlock(void);
static void     filt_timerunlock(void);

static zone_t   knote_zone;

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

#if 0
extern struct filterops aio_filtops;
#endif

/* Mach portset filter */
extern struct filterops machport_filtops;

/* User filter */
static int      filt_userattach(struct knote *kn);
static void     filt_userdetach(struct knote *kn);
static int      filt_user(struct knote *kn, long hint);
static void     filt_usertouch(struct knote *kn, struct kevent64_s *kev, 
                long type);
static struct filterops user_filtops = {
        .f_attach = filt_userattach,
        .f_detach = filt_userdetach,
        .f_event = filt_user,
        .f_touch = filt_usertouch,
};

/*
 * Table for for all system-defined filters.
 */
static struct filterops *sysfilt_ops[] = {
        &file_filtops,                  /* EVFILT_READ */
        &file_filtops,                  /* EVFILT_WRITE */
#if 0
        &aio_filtops,                   /* EVFILT_AIO */
#else
        &bad_filtops,                   /* EVFILT_AIO */
#endif
        &file_filtops,                  /* EVFILT_VNODE */
        &proc_filtops,                  /* EVFILT_PROC */
        &sig_filtops,                   /* EVFILT_SIGNAL */
        &timer_filtops,                 /* EVFILT_TIMER */
        &machport_filtops,              /* EVFILT_MACHPORT */
        &fs_filtops,                    /* EVFILT_FS */
        &user_filtops,                  /* EVFILT_USER */
        &bad_filtops,                   /* unused */
        &vm_filtops,                    /* EVFILT_VM */
};

/*
 * kqueue/note lock attributes and implementations
 *
 *      kqueues have locks, while knotes have use counts
 *      Most of the knote state is guarded by the object lock.
 *      the knote "inuse" count and status use the kqueue lock.
 */
lck_grp_attr_t * kq_lck_grp_attr;
lck_grp_t * kq_lck_grp;
lck_attr_t * kq_lck_attr;

static inline void
kqlock(struct kqueue *kq)
{
        lck_spin_lock(&kq->kq_lock);
}

static inline void
kqunlock(struct kqueue *kq)
{
        lck_spin_unlock(&kq->kq_lock);
}

/* 
 * Convert a kq lock to a knote use referece.
 *
 *      If the knote is being dropped, we can't get
 *      a use reference, so just return with it
 *      still locked.
 *      
 *      - kq locked at entry
 *      - unlock on exit if we get the use reference
 */
static int
kqlock2knoteuse(struct kqueue *kq, struct knote *kn)
{
        if (kn->kn_status & KN_DROPPING)
                return 0;
        kn->kn_inuse++;
        kqunlock(kq);
        return 1;
 }

/* 
 * Convert a kq lock to a knote use referece,
 * but wait for attach and drop events to complete.
 *
 *      If the knote is being dropped, we can't get
 *      a use reference, so just return with it
 *      still locked.
 *      
 *      - kq locked at entry
 *      - kq always unlocked on exit
 */
static int
kqlock2knoteusewait(struct kqueue *kq, struct knote *kn)
{
        if ((kn->kn_status & (KN_DROPPING | KN_ATTACHING)) != 0) {
                kn->kn_status |= KN_USEWAIT;
                wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_UNINT, 0);
                kqunlock(kq);
                thread_block(THREAD_CONTINUE_NULL);
                return 0;
        }
        kn->kn_inuse++;
        kqunlock(kq);
        return 1;
 }


/* 
 * Convert from a knote use reference back to kq lock.
 *
 *      Drop a use reference and wake any waiters if
 *      this is the last one.
 *
 *      The exit return indicates if the knote is
 *      still alive - but the kqueue lock is taken
 *      unconditionally.
 */
static int
knoteuse2kqlock(struct kqueue *kq, struct knote *kn)
{
        kqlock(kq);
        if (--kn->kn_inuse == 0) {
                if ((kn->kn_status & KN_ATTACHING) != 0) {
                        kn->kn_status &= ~KN_ATTACHING;
                }
                if ((kn->kn_status & KN_USEWAIT) != 0) {
                        kn->kn_status &= ~KN_USEWAIT;
                        wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_AWAKENED);
                }
        }
        return ((kn->kn_status & KN_DROPPING) == 0);
 }

/* 
 * Convert a kq lock to a knote drop referece.
 *
 *      If the knote is in use, wait for the use count
 *      to subside.  We first mark our intention to drop
 *      it - keeping other users from "piling on."
 *      If we are too late, we have to wait for the
 *      other drop to complete.
 *      
 *      - kq locked at entry
 *      - always unlocked on exit.
 *      - caller can't hold any locks that would prevent
 *        the other dropper from completing.
 */
static int
kqlock2knotedrop(struct kqueue *kq, struct knote *kn)
{
        int oktodrop;

        oktodrop = ((kn->kn_status & (KN_DROPPING | KN_ATTACHING)) == 0);
        kn->kn_status |= KN_DROPPING;
        if (oktodrop) {
                if (kn->kn_inuse == 0) {
                        kqunlock(kq);
                        return oktodrop;
                }
        }
        kn->kn_status |= KN_USEWAIT;
        wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_UNINT, 0);
        kqunlock(kq);
        thread_block(THREAD_CONTINUE_NULL);
        return oktodrop;
}
                
/* 
 * Release a knote use count reference.
 */
static void
knote_put(struct knote *kn)
{
        struct kqueue *kq = kn->kn_kq;

        kqlock(kq);
        if (--kn->kn_inuse == 0) {
                if ((kn->kn_status & KN_USEWAIT) != 0) {
                        kn->kn_status &= ~KN_USEWAIT;
                        wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_AWAKENED);
                }
        }
        kqunlock(kq);
 }

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

#define f_flag f_fglob->fg_flag
#define f_type f_fglob->fg_type
#define f_msgcount f_fglob->fg_msgcount
#define f_cred f_fglob->fg_cred
#define f_ops f_fglob->fg_ops
#define f_offset f_fglob->fg_offset
#define f_data f_fglob->fg_data

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

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

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

        kn->kn_data = kq->kq_count;
        return (kn->kn_data > 0);
}

static int
filt_procattach(struct knote *kn)
{
        struct proc *p;
        pid_t selfpid = (pid_t)0;

        assert(PID_MAX < NOTE_PDATAMASK);
        
        if ((kn->kn_sfflags & (NOTE_TRACK | NOTE_TRACKERR | NOTE_CHILD)) != 0)
                return(ENOTSUP);

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

        if ((kn->kn_sfflags & NOTE_EXIT) != 0) {
                selfpid = proc_selfpid();
                /* check for validity of NOTE_EXISTATUS */
                if (((kn->kn_sfflags & NOTE_EXITSTATUS) != 0) && 
                        ((p->p_ppid != selfpid) && (((p->p_lflag & P_LTRACED) == 0) || (p->p_oppid != selfpid)))) {
                        proc_rele(p);
                        return(EACCES);
                }
        }

        proc_klist_lock();

        kn->kn_flags |= EV_CLEAR;       /* automatically set */
        kn->kn_ptr.p_proc = p;          /* store the proc handle */

        KNOTE_ATTACH(&p->p_klist, kn);

        proc_klist_unlock();

        proc_rele(p);

        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)
{
        /* hint is 0 when called from above */
        if (hint != 0) {
                u_int event;

                /* ALWAYS CALLED WITH proc_klist_lock when (hint != 0) */

                /*
                 * 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;

                if (event == NOTE_REAP || (event == NOTE_EXIT && !(kn->kn_sfflags & NOTE_REAP))) {
                        kn->kn_flags |= (EV_EOF | EV_ONESHOT);
                }
                if ((event == NOTE_EXIT) && ((kn->kn_sfflags & NOTE_EXITSTATUS) != 0)) {
                        kn->kn_fflags |= NOTE_EXITSTATUS;
                        kn->kn_data = (hint & NOTE_PDATAMASK);
                }
                if ((event == NOTE_RESOURCEEND) && ((kn->kn_sfflags & NOTE_RESOURCEEND) != 0)) {
                        kn->kn_fflags |= NOTE_RESOURCEEND;
                        kn->kn_data = (hint & NOTE_PDATAMASK);
                }
        }

        /* atomic check, no locking need when called from above */
        return (kn->kn_fflags != 0); 
}

/*
 * Virtual memory kevents
 *
 * author: Matt Jacobson [matthew_jacobson@apple.com]
 */

static int
filt_vmattach(struct knote *kn)
{       
        /* 
         * The note will be cleared once the information has been flushed to the client. 
         * If there is still pressure, we will be re-alerted.
         */
        kn->kn_flags |= EV_CLEAR; 
        
        return vm_knote_register(kn);
}

static void
filt_vmdetach(struct knote *kn)
{
        vm_knote_unregister(kn);
}

static int
filt_vm(struct knote *kn, long hint)
{
        /* hint == 0 means this is just an alive? check (always true) */
        if (hint != 0) { 
                /* If this knote is interested in the event specified in hint... */
                if ((kn->kn_sfflags & hint) != 0) { 
                        kn->kn_fflags |= hint;
                }
        }
        
        return (kn->kn_fflags != 0);
}

/*
 * filt_timervalidate - process data from user
 *      
 *      Converts to either interval or deadline format.
 *      
 *      The saved-data field in the knote contains the
 *      time value.  The saved filter-flags indicates
 *      the unit of measurement.
 *
 *      After validation, either the saved-data field 
 *      contains the interval in absolute time, or ext[0] 
 *      contains the expected deadline. If that deadline 
 *      is in the past, ext[0] is 0.
 *
 *      Returns EINVAL for unrecognized units of time.
 *
 *      Timer filter lock is held.
 *
 */
static int
filt_timervalidate(struct knote *kn)
{
        uint64_t multiplier;
        uint64_t raw;

        switch (kn->kn_sfflags & (NOTE_SECONDS|NOTE_USECONDS|NOTE_NSECONDS)) {
        case NOTE_SECONDS:
                multiplier = NSEC_PER_SEC;
                break;
        case NOTE_USECONDS:
                multiplier = NSEC_PER_USEC;
                break;
        case NOTE_NSECONDS:
                multiplier = 1;
                break;
        case 0: /* milliseconds (default) */
                multiplier = NSEC_PER_SEC / 1000;
                break;
        default:
                return EINVAL;
        }

        nanoseconds_to_absolutetime((uint64_t)kn->kn_sdata * multiplier, &raw);

        kn->kn_ext[0] = 0;
        kn->kn_sdata = 0;

        if (kn->kn_sfflags & NOTE_ABSOLUTE) {
                clock_sec_t seconds;
                clock_nsec_t nanoseconds;
                uint64_t now;

                clock_get_calendar_nanotime(&seconds, &nanoseconds);
                nanoseconds_to_absolutetime((uint64_t)seconds * NSEC_PER_SEC + 
                                nanoseconds, &now);

                if (raw < now) {
                        /* time has already passed */
                        kn->kn_ext[0] = 0;
                } else {
                        raw -= now;
                        clock_absolutetime_interval_to_deadline(raw, 
                                        &kn->kn_ext[0]);
                }
        } else {
                kn->kn_sdata = raw;
        }

        return 0;
}

/*
 * filt_timerupdate - compute the next deadline
 *
 *      Repeating timers store their interval in kn_sdata. Absolute
 *      timers have already calculated the deadline, stored in ext[0].
 *
 *      On return, the next deadline (or zero if no deadline is needed)
 *      is stored in kn_ext[0].
 *
 *      Timer filter lock is held.
 */
static void 
filt_timerupdate(struct knote *kn)
{
        /* if there's no interval, deadline is just in kn_ext[0] */
        if (kn->kn_sdata == 0)
                return;

        /* if timer hasn't fired before, fire in interval nsecs */
        if (kn->kn_ext[0] == 0) {
                clock_absolutetime_interval_to_deadline(kn->kn_sdata,
                                &kn->kn_ext[0]);
        } else {
                /* 
                 * If timer has fired before, schedule the next pop 
                 * relative to the last intended deadline. 
                 *
                 * We could check for whether the deadline has expired, 
                 * but the thread call layer can handle that.
                 */
                kn->kn_ext[0] += kn->kn_sdata;
        }
}

/* 
 * filt_timerexpire - the timer callout routine
 *
 *      Just propagate the timer event into the knote
 *      filter routine (by going through the knote
 *      synchronization point).  Pass a hint to
 *      indicate this is a real event, not just a
 *      query from above.
 */
static void
filt_timerexpire(void *knx, __unused void *spare)
{
        struct klist timer_list;
        struct knote *kn = knx;

        filt_timerlock();

        kn->kn_hookid &= ~TIMER_RUNNING;

        /* no "object" for timers, so fake a list */
        SLIST_INIT(&timer_list);
        SLIST_INSERT_HEAD(&timer_list, kn, kn_selnext); 
        KNOTE(&timer_list, 1);

        /* if someone is waiting for timer to pop */
        if (kn->kn_hookid & TIMER_CANCELWAIT) {
                struct kqueue *kq = kn->kn_kq;
                wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_hook, 
                                THREAD_AWAKENED);
        }

        filt_timerunlock();
}

/*
 * Cancel a running timer (or wait for the pop).
 * Timer filter lock is held.
 */
static void
filt_timercancel(struct knote *kn)
{
        struct kqueue *kq = kn->kn_kq;
        thread_call_t callout = kn->kn_hook;
        boolean_t cancelled;

        if (kn->kn_hookid & TIMER_RUNNING) {
                /* cancel the callout if we can */
                cancelled = thread_call_cancel(callout);
                if (cancelled) {
                        kn->kn_hookid &= ~TIMER_RUNNING;
                } else {
                        /* we have to wait for the expire routine.  */
                        kn->kn_hookid |= TIMER_CANCELWAIT;
                        wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, 
                                        &kn->kn_hook, THREAD_UNINT, 0);
                        filt_timerunlock();
                        thread_block(THREAD_CONTINUE_NULL);
                        filt_timerlock();
                        assert((kn->kn_hookid & TIMER_RUNNING) == 0);
                }
        }
}

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

        callout = thread_call_allocate(filt_timerexpire, kn);
        if (NULL == callout)
                return (ENOMEM);

        filt_timerlock();
        error = filt_timervalidate(kn);
        if (error) {
                filt_timerunlock();
                return (error);
        }

        kn->kn_hook = (void*)callout;
        kn->kn_hookid = 0;

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

        filt_timerupdate(kn);
        if (kn->kn_ext[0]) {
                kn->kn_flags |= EV_CLEAR;
                thread_call_enter_delayed(callout, kn->kn_ext[0]);
                kn->kn_hookid |= TIMER_RUNNING;
        } else {
                /* fake immediate */
                kn->kn_data = 1;
        }

        filt_timerunlock();
        return (0);
}

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

        filt_timerlock();

        callout = (thread_call_t)kn->kn_hook;
        filt_timercancel(kn);
        
        filt_timerunlock(); 

        thread_call_free(callout);
}



static int
filt_timer(struct knote *kn, long hint)
{
        int result;
        
        if (hint) {
                /* real timer pop -- timer lock held by filt_timerexpire */

                kn->kn_data++;

                if (((kn->kn_hookid & TIMER_CANCELWAIT) == 0) && 
                                ((kn->kn_flags & EV_ONESHOT) == 0)) {

                        /* evaluate next time to fire */
                        filt_timerupdate(kn);

                        if (kn->kn_ext[0]) {
                                /* keep the callout and re-arm */
                                thread_call_enter_delayed(kn->kn_hook, 
                                                kn->kn_ext[0]);
                                kn->kn_hookid |= TIMER_RUNNING;
                        }
                }

                return 1;
        } 

        /* user-query */
        filt_timerlock();

        result = (kn->kn_data != 0);

        filt_timerunlock();
        return result;
}


/*
 * filt_timertouch - update 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 void     
filt_timertouch(struct knote *kn, struct kevent64_s *kev, long type)
{
        int error;
        filt_timerlock();

        switch (type) {
        case EVENT_REGISTER:
                /* cancel current call */
                filt_timercancel(kn);

                /* recalculate deadline */
                kn->kn_sdata = kev->data;
                kn->kn_sfflags = kev->fflags;

                error = filt_timervalidate(kn);
                if (error) {
                        /* no way to report error, so mark it in the knote */
                        kn->kn_flags |= EV_ERROR;
                        kn->kn_data = error;
                        break;
                } 

                /* start timer if necessary */
                filt_timerupdate(kn);
                if (kn->kn_ext[0]) {
                        thread_call_enter_delayed(kn->kn_hook, kn->kn_ext[0]);
                        kn->kn_hookid |= TIMER_RUNNING;
                } else {
                        /* pretend the timer has fired */
                        kn->kn_data = 1;
                }

                break;

        case EVENT_PROCESS:
                /* reset the timer pop count in kn_data */
                *kev = kn->kn_kevent;
                kev->ext[0] = 0;
                kn->kn_data = 0;
                if (kn->kn_flags & EV_CLEAR)
                        kn->kn_fflags = 0;
                break;
        default:
                panic("filt_timertouch() - invalid type (%ld)", type);
                break;
        }

        filt_timerunlock();
}

static void
filt_timerlock(void)
{
        lck_mtx_lock(&_filt_timerlock);
}

static void
filt_timerunlock(void)
{
        lck_mtx_unlock(&_filt_timerlock);
}

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 kevent64_s *kev, long type)
{
        uint32_t ffctrl;
        switch (type) {
        case EVENT_REGISTER:
                if (kev->fflags & NOTE_TRIGGER) {
                        kn->kn_hookid = 1;
                }

                ffctrl = kev->fflags & NOTE_FFCTRLMASK;
                kev->fflags &= NOTE_FFLAGSMASK;
                switch (ffctrl) {
                case NOTE_FFNOP:
                        break;
                case NOTE_FFAND:
                        OSBitAndAtomic(kev->fflags, &kn->kn_sfflags);
                        break;
                case NOTE_FFOR:
                        OSBitOrAtomic(kev->fflags, &kn->kn_sfflags);
                        break;
                case NOTE_FFCOPY:
                        kn->kn_sfflags = kev->fflags;
                        break;
                }
                kn->kn_sdata = kev->data;
                break;
        case EVENT_PROCESS:
                *kev = kn->kn_kevent;
                kev->fflags = (volatile UInt32)kn->kn_sfflags;
                kev->data = kn->kn_sdata;
                if (kn->kn_flags & EV_CLEAR) {
                        kn->kn_hookid = 0;
                        kn->kn_data = 0;
                        kn->kn_fflags = 0;
                }
                break;
        default:
                panic("filt_usertouch() - invalid type (%ld)", type);
                break;
        }
}

/*
 * JMM - placeholder for not-yet-implemented filters
 */ 
static int
filt_badattach(__unused struct knote *kn)
{
        return(ENOTSUP);
}


struct kqueue *
kqueue_alloc(struct proc *p)
{
        struct filedesc *fdp = p->p_fd;
        struct kqueue *kq;

        MALLOC_ZONE(kq, struct kqueue *, sizeof(struct kqueue), M_KQUEUE, M_WAITOK);
        if (kq != NULL) {
                wait_queue_set_t wqs;

                wqs = wait_queue_set_alloc(SYNC_POLICY_FIFO | SYNC_POLICY_PREPOST);
                if (wqs != NULL) {
                        bzero(kq, sizeof(struct kqueue));
                        lck_spin_init(&kq->kq_lock, kq_lck_grp, kq_lck_attr);
                        TAILQ_INIT(&kq->kq_head);
                        kq->kq_wqs = wqs;
                        kq->kq_p = p;
                } else {
                        FREE_ZONE(kq, sizeof(struct kqueue), M_KQUEUE);
                }
        }

        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;
}


/*
 * kqueue_dealloc - detach all knotes from a kqueue and free it
 *
 *      We walk each list looking for knotes referencing this
 *      this kqueue.  If we find one, we try to drop it.  But
 *      if we fail to get a drop reference, that will wait
 *      until it is dropped.  So, we can just restart again
 *      safe in the assumption that the list will eventually
 *      not contain any more references to this kqueue (either
 *      we dropped them all, or someone else did).
 *
 *      Assumes no new events are being added to the kqueue.
 *      Nothing locked on entry or exit.
 */
void
kqueue_dealloc(struct kqueue *kq)
{
        struct proc *p = kq->kq_p;
        struct filedesc *fdp = p->p_fd;
        struct knote *kn;
        int i;

        proc_fdlock(p);
        for (i = 0; i < fdp->fd_knlistsize; i++) {
                kn = SLIST_FIRST(&fdp->fd_knlist[i]);
                while (kn != NULL) {
                        if (kq == kn->kn_kq) {
                                kqlock(kq);
                                proc_fdunlock(p);
                                /* drop it ourselves or wait */
                                if (kqlock2knotedrop(kq, kn)) {
                                        kn->kn_fop->f_detach(kn);
                                        knote_drop(kn, p);
                                }
                                proc_fdlock(p);
                                /* start over at beginning of list */
                                kn = SLIST_FIRST(&fdp->fd_knlist[i]);
                                continue;
                        }
                        kn = SLIST_NEXT(kn, kn_link);
                }
        }
        if (fdp->fd_knhashmask != 0) {
                for (i = 0; i < (int)fdp->fd_knhashmask + 1; i++) {
                        kn = SLIST_FIRST(&fdp->fd_knhash[i]);
                        while (kn != NULL) {
                                if (kq == kn->kn_kq) {
                                        kqlock(kq);
                                        proc_fdunlock(p);
                                        /* drop it ourselves or wait */
                                        if (kqlock2knotedrop(kq, kn)) {
                                                kn->kn_fop->f_detach(kn);
                                                knote_drop(kn, p);
                                        }
                                        proc_fdlock(p);
                                        /* start over at beginning of list */
                                        kn = SLIST_FIRST(&fdp->fd_knhash[i]);
                                        continue;
                                }
                                kn = SLIST_NEXT(kn, kn_link);
                        }
                }
        }
        proc_fdunlock(p);

        /* 
         * before freeing the wait queue set for this kqueue,
         * make sure it is unlinked from all its containing (select) sets.
         */
        wait_queue_unlink_all((wait_queue_t)kq->kq_wqs);
        wait_queue_set_free(kq->kq_wqs);
        lck_spin_destroy(&kq->kq_lock, kq_lck_grp);
        FREE_ZONE(kq, sizeof(struct kqueue), M_KQUEUE);
}

int
kqueue(struct proc *p, __unused struct kqueue_args *uap, int32_t *retval)
{
        struct kqueue *kq;
        struct fileproc *fp;
        int fd, error;

        error = falloc(p, &fp, &fd, vfs_context_current());
        if (error) {
                return (error);
        }

        kq = kqueue_alloc(p);
        if (kq == NULL) {
                fp_free(p, fd, fp);
                return (ENOMEM);
        }

        fp->f_flag = FREAD | FWRITE;
        fp->f_type = DTYPE_KQUEUE;
        fp->f_ops = &kqueueops;
        fp->f_data = (caddr_t)kq;

        proc_fdlock(p);
        procfdtbl_releasefd(p, fd, NULL);
        fp_drop(p, fd, fp, 1);
        proc_fdunlock(p);

        *retval = fd;
        return (error);
}

static int
kevent_copyin(user_addr_t *addrp, struct kevent64_s *kevp, struct proc *p, int iskev64)
{
        int advance;
        int error;

        if (iskev64) {
                advance = sizeof(struct kevent64_s);
                error = copyin(*addrp, (caddr_t)kevp, advance);
        } else if (IS_64BIT_PROCESS(p)) {
                struct user64_kevent kev64;
                bzero(kevp, sizeof(struct kevent64_s));

                advance = sizeof(kev64);
                error = copyin(*addrp, (caddr_t)&kev64, advance);
                if (error)
                        return error;
                kevp->ident = kev64.ident;
                kevp->filter = kev64.filter;
                kevp->flags = kev64.flags;
                kevp->fflags = kev64.fflags;
                kevp->data = kev64.data;
                kevp->udata = kev64.udata;
        } else {
                struct user32_kevent kev32;
                bzero(kevp, sizeof(struct kevent64_s));

                advance = sizeof(kev32);
                error = copyin(*addrp, (caddr_t)&kev32, advance);
                if (error)
                        return error;
                kevp->ident = (uintptr_t)kev32.ident;
                kevp->filter = kev32.filter;
                kevp->flags = kev32.flags;
                kevp->fflags = kev32.fflags;
                kevp->data = (intptr_t)kev32.data;
                kevp->udata = CAST_USER_ADDR_T(kev32.udata);
        }
        if (!error)
                *addrp += advance;
        return error;
}

static int
kevent_copyout(struct kevent64_s *kevp, user_addr_t *addrp, struct proc *p, int iskev64)
{
        int advance;
        int error;

        if (iskev64) {
                advance = sizeof(struct kevent64_s);
                error = copyout((caddr_t)kevp, *addrp, advance);
        } else if (IS_64BIT_PROCESS(p)) {
                struct user64_kevent kev64;

                /*
                 * 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;
                advance = sizeof(kev64);
                error = copyout((caddr_t)&kev64, *addrp, advance);
        } else {
                struct user32_kevent kev32;

                kev32.ident = (uint32_t)kevp->ident;
                kev32.filter = kevp->filter;
                kev32.flags = kevp->flags;
                kev32.fflags = kevp->fflags;
                kev32.data = (int32_t)kevp->data;
                kev32.udata = kevp->udata;
                advance = sizeof(kev32);
                error = copyout((caddr_t)&kev32, *addrp, advance);
        }
        if (!error)
                *addrp += advance;
        return error;
}

/*
 * kevent_continue - continue a kevent syscall after blocking
 *
 *      assume we inherit a use count on the kq fileglob.
 */

static void
kevent_continue(__unused struct kqueue *kq, void *data, int error)
{
        struct _kevent *cont_args;
        struct fileproc *fp;
        int32_t *retval;
        int noutputs;
        int fd;
        struct proc *p = current_proc();

        cont_args = (struct _kevent *)data;
        noutputs = cont_args->eventout;
        retval = cont_args->retval;
        fd = cont_args->fd;
        fp = cont_args->fp;

        fp_drop(p, fd, fp, 0);

        /* 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)
{
        return kevent_internal(p, 
                        0, 
                        uap->changelist,
                        uap->nchanges,
                        uap->eventlist,
                        uap->nevents,
                        uap->fd,
                        uap->timeout,
                        0, /* no flags from old kevent() call */
                        retval);
}
  
int
kevent64(struct proc *p, struct kevent64_args *uap, int32_t *retval)
{
        return kevent_internal(p, 
                        1, 
                        uap->changelist,
                        uap->nchanges,
                        uap->eventlist,
                        uap->nevents,
                        uap->fd,
                        uap->timeout,
                        uap->flags,
                        retval);
}

static int
kevent_internal(struct proc *p, int iskev64, user_addr_t changelist, 
                int nchanges, user_addr_t ueventlist, int nevents, int fd, 
                user_addr_t utimeout, __unused unsigned int flags, 
                int32_t *retval)
{
        struct _kevent *cont_args;
        uthread_t ut;
        struct kqueue *kq;
        struct fileproc *fp;
        struct kevent64_s kev;
        int error, noutputs;
        struct timeval atv;

        /* convert timeout to absolute - if we have one */
        if (utimeout != USER_ADDR_NULL) {
                struct timeval rtv;
                if (IS_64BIT_PROCESS(p)) {
                        struct user64_timespec ts;
                        error = copyin(utimeout, &ts, sizeof(ts));
                        if ((ts.tv_sec & 0xFFFFFFFF00000000ull) != 0)
                                error = EINVAL;
                        else
                                TIMESPEC_TO_TIMEVAL(&rtv, &ts);
                } 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 {
                atv.tv_sec = 0;
                atv.tv_usec = 0;
        }

        /* get a usecount for the kq itself */
        if ((error = fp_getfkq(p, fd, &fp, &kq)) != 0)
                return(error);
        
        /* each kq should only be used for events of one type */
        kqlock(kq);
        if (kq->kq_state & (KQ_KEV32 | KQ_KEV64)) {
                if (((iskev64 && (kq->kq_state & KQ_KEV32)) ||
                        (!iskev64 && (kq->kq_state & KQ_KEV64)))) {
                        error = EINVAL;
                        kqunlock(kq);
                        goto errorout;
                }
        } else {
                kq->kq_state |= (iskev64 ? KQ_KEV64 : KQ_KEV32);
        }
        kqunlock(kq);

        /* register all the change requests the user provided... */
        noutputs = 0;
        while (nchanges > 0 && error == 0) {
                error = kevent_copyin(&changelist, &kev, p, iskev64);
                if (error)
                        break;
                                
                kev.flags &= ~EV_SYSFLAGS;
                error = kevent_register(kq, &kev, p);
                if ((error || (kev.flags & EV_RECEIPT)) && nevents > 0) {
                        kev.flags = EV_ERROR;
                        kev.data = error;
                        error = kevent_copyout(&kev, &ueventlist, p, iskev64);
                        if (error == 0) {
                                nevents--;
                                noutputs++;
                        }
                }
                nchanges--;
        }

        /* store the continuation/completion data in the uthread */
        ut = (uthread_t)get_bsdthread_info(current_thread());
        cont_args = &ut->uu_kevent.ss_kevent;
        cont_args->fp = fp;
        cont_args->fd = fd;
        cont_args->retval = retval;
        cont_args->eventlist = ueventlist;
        cont_args->eventcount = nevents;
        cont_args->eventout = noutputs;
        cont_args->eventsize = iskev64;

        if (nevents > 0 && noutputs == 0 && error == 0)
                error = kqueue_scan(kq, kevent_callback,
                                    kevent_continue, cont_args,
                                    &atv, p);
        kevent_continue(kq, cont_args, error);

errorout:
        fp_drop(p, fd, fp, 0);
        return error;
}


/*
 * 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 kevent64_s *kevp, 
                void *data)
{
        struct _kevent *cont_args;
        int error;
        int iskev64;

        cont_args = (struct _kevent *)data;
        assert(cont_args->eventout < cont_args->eventcount);

        iskev64 = cont_args->eventsize;

        /*
         * Copy out the appropriate amount of event data for this user.
         */
        error = kevent_copyout(kevp, &cont_args->eventlist, current_proc(), iskev64);

        /*
         * 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 128-byte string buffer
 */

char *
kevent_description(struct kevent64_s *kevp, char *s, size_t n)
{
        snprintf(s, n,
                 "kevent="
                 "{.ident=%#llx, .filter=%d, .flags=%#x, .fflags=%#x, .data=%#llx, .udata=%#llx, .ext[0]=%#llx, .ext[1]=%#llx}",
                 kevp->ident,
                 kevp->filter,
                 kevp->flags,
                 kevp->fflags,
                 kevp->data,
                 kevp->udata,
                 kevp->ext[0],
                 kevp->ext[1]);
        return s;
}

/*
 * 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 kevent64_s *kev, __unused struct proc *ctxp)
{
        struct proc *p = kq->kq_p;
        struct filedesc *fdp = p->p_fd;
        struct filterops *fops;
        struct fileproc *fp = NULL;
        struct knote *kn = NULL;
        int error = 0;

        if (kev->filter < 0) {
                if (kev->filter + EVFILT_SYSCOUNT < 0)
                        return (EINVAL);
                fops = sysfilt_ops[~kev->filter];       /* to 0-base index */
        } else {
                /*
                 * XXX
                 * filter attach routine is responsible for insuring that
                 * the identifier can be attached to it.
                 */
                printf("unknown filter: %d\n", kev->filter);
                return (EINVAL);
        }

 restart:
        /* this iocount needs to be dropped if it is not registered */
        proc_fdlock(p);
        if (fops->f_isfd && (error = fp_lookup(p, kev->ident, &fp, 1)) != 0) {
                proc_fdunlock(p);
                return(error);
        }

        if (fops->f_isfd) {
                /* fd-based knotes are linked off the fd table */
                if (kev->ident < (u_int)fdp->fd_knlistsize) {
                        SLIST_FOREACH(kn, &fdp->fd_knlist[kev->ident], kn_link)
                                if (kq == kn->kn_kq &&
                                    kev->filter == kn->kn_filter)
                                        break;
                }
        } else {
                /* hash non-fd knotes here too */
                if (fdp->fd_knhashmask != 0) {
                        struct klist *list;
                        
                        list = &fdp->fd_knhash[
                            KN_HASH((u_long)kev->ident, fdp->fd_knhashmask)];
                        SLIST_FOREACH(kn, list, kn_link)
                                if (kev->ident == kn->kn_id &&
                                    kq == kn->kn_kq &&
                                    kev->filter == kn->kn_filter)
                                        break;
                }
        }

        /*
         * kn now contains the matching knote, or NULL if no match
         */
        if (kn == NULL) {
                if ((kev->flags & (EV_ADD|EV_DELETE)) == EV_ADD) {
                        kn = knote_alloc();
                        if (kn == NULL) {
                                proc_fdunlock(p);
                                error = ENOMEM;
                                goto done;
                        }
                        kn->kn_fp = fp;
                        kn->kn_kq = kq;
                        kn->kn_tq = &kq->kq_head;
                        kn->kn_fop = fops;
                        kn->kn_sfflags = kev->fflags;
                        kn->kn_sdata = kev->data;
                        kev->fflags = 0;
                        kev->data = 0;
                        kn->kn_kevent = *kev;
                        kn->kn_inuse = 1;  /* for f_attach() */
                        kn->kn_status = KN_ATTACHING;

                        /* before anyone can find it */
                        if (kev->flags & EV_DISABLE)
                                kn->kn_status |= KN_DISABLED;

                        error = knote_fdpattach(kn, fdp, p);
                        proc_fdunlock(p);

                        if (error) {
                                knote_free(kn);
                                goto done;
                        }

                        /*
                         * apply reference count to knote structure, and
                         * do not release it at the end of this routine.
                         */
                        fp = NULL;

                        error = fops->f_attach(kn);

                        kqlock(kq);

                        if (error != 0) {
                                /*
                                 * Failed to attach correctly, so drop.
                                 * All other possible users/droppers
                                 * have deferred to us.
                                 */
                                kn->kn_status |= KN_DROPPING;
                                kqunlock(kq);
                                knote_drop(kn, p);
                                goto done;
                        } else if (kn->kn_status & KN_DROPPING) {
                                /*
                                 * Attach succeeded, but someone else
                                 * deferred their drop - now we have
                                 * to do it for them (after detaching).
                                 */
                                kqunlock(kq);
                                kn->kn_fop->f_detach(kn);
                                knote_drop(kn, p);
                                goto done;
                        }
                        kn->kn_status &= ~KN_ATTACHING;
                        kqunlock(kq);
                } else {
                        proc_fdunlock(p);
                        error = ENOENT;
                        goto done;
                }
        } else {
                /* existing knote - get kqueue lock */
                kqlock(kq);
                proc_fdunlock(p);
                
                if (kev->flags & EV_DELETE) {
                        knote_dequeue(kn);
                        kn->kn_status |= KN_DISABLED;
                        if (kqlock2knotedrop(kq, kn)) {
                                kn->kn_fop->f_detach(kn);
                                knote_drop(kn, p);
                        }
                        goto done;
                }
                        
                /* update status flags for existing knote */
                if (kev->flags & EV_DISABLE) {
                        knote_dequeue(kn);
                        kn->kn_status |= KN_DISABLED;
                } else if (kev->flags & EV_ENABLE) {
                        kn->kn_status &= ~KN_DISABLED;
                        if (kn->kn_status & KN_ACTIVE)
                                knote_enqueue(kn);
                }

                /*
                 * The user may change some filter values after the
                 * initial EV_ADD, but doing so will not reset any 
                 * filter which have already been triggered.
                 */
                kn->kn_kevent.udata = kev->udata;
                if (fops->f_isfd || fops->f_touch == NULL) {
                        kn->kn_sfflags = kev->fflags;
                        kn->kn_sdata = kev->data;
                }

                /*
                 * If somebody is in the middle of dropping this
                 * knote - go find/insert a new one.  But we have
                 * wait for this one to go away first. Attaches
                 * running in parallel may also drop/modify the
                 * knote.  Wait for those to complete as well and
                 * then start over if we encounter one.
                 */
                if (!kqlock2knoteusewait(kq, kn)) {
                        /* kqueue, proc_fdlock both unlocked */
                        goto restart;
                }

                /*
                 * Call touch routine to notify filter of changes
                 * in filter values.
                 */
                if (!fops->f_isfd && fops->f_touch != NULL)
                        fops->f_touch(kn, kev, EVENT_REGISTER);
        }
        /* still have use ref on knote */

        /*
         * If the knote is not marked to always stay enqueued,
         * invoke the filter routine to see if it should be
         * enqueued now.
         */
        if ((kn->kn_status & KN_STAYQUEUED) == 0 && kn->kn_fop->f_event(kn, 0)) {
                if (knoteuse2kqlock(kq, kn))
                        knote_activate(kn, 1);
                kqunlock(kq);
        } else {
                knote_put(kn);
        }

done:
        if (fp != NULL)
                fp_drop(p, kev->ident, fp, 0);
        return (error);
}


/*
 * knote_process - process a triggered event
 *
 *      Validate that it is really still a triggered event
 *      by calling the filter routines (if necessary).  Hold
 *      a use reference on the knote to avoid it being detached.
 *      If it is still considered triggered, invoke the callback
 *      routine provided and move it to the provided inprocess
 *      queue.
 *
 *      caller holds a reference on the kqueue.
 *      kqueue locked on entry and exit - but may be dropped
 */
static int
knote_process(struct knote      *kn,
              kevent_callback_t callback,
              void              *data, 
              struct kqtailq    *inprocessp, 
              struct proc       *p)
{
        struct kqueue *kq = kn->kn_kq;
        struct kevent64_s kev;
        int touch;
        int result;
        int error;

        /*
         * Determine the kevent state we want to return.
         *
         * Some event states need to be revalidated before returning
         * them, others we take the snapshot at the time the event
         * was enqueued.
         *
         * Events with non-NULL f_touch operations must be touched.
         * Triggered events must fill in kev for the callback.
         *
         * Convert our lock to a use-count and call the event's
         * filter routine(s) to update.
         */
        if ((kn->kn_status & KN_DISABLED) != 0) {
                result = 0;
                touch = 0;
        } else {
                int revalidate;

                result = 1;
                revalidate = ((kn->kn_status & KN_STAYQUEUED) != 0 ||
                              (kn->kn_flags & EV_ONESHOT) == 0);
                touch = (!kn->kn_fop->f_isfd && kn->kn_fop->f_touch != NULL);

                if (revalidate || touch) {
                        if (revalidate)
                                knote_deactivate(kn);
                        
                        /* call the filter/touch routines with just a ref */
                        if (kqlock2knoteuse(kq, kn)) {
                        
                                /* if we have to revalidate, call the filter */
                                if (revalidate) {
                                        result = kn->kn_fop->f_event(kn, 0);
                                }

                                /* capture the kevent data - using touch if specified */
                                if (result && touch) {
                                        kn->kn_fop->f_touch(kn, &kev, EVENT_PROCESS);
                                }

                                /* convert back to a kqlock - bail if the knote went away */
                                if (!knoteuse2kqlock(kq, kn)) {
                                        return EJUSTRETURN;
                                } else if (result) {
                                        /* if revalidated as alive, make sure it's active */
                                        if (!(kn->kn_status & KN_ACTIVE)) {
                                                knote_activate(kn, 0);
                                        }

                                        /* capture all events that occurred during filter */
                                        if (!touch) {
                                                kev = kn->kn_kevent;
                                        }

                                } else if ((kn->kn_status & KN_STAYQUEUED) == 0) {
                                        /* was already dequeued, so just bail on this one */
                                        return EJUSTRETURN;
                                }
                        } else {
                                return EJUSTRETURN;
                        }
                } else {
                        kev = kn->kn_kevent;
                }
        }
                
        /* move knote onto inprocess queue */
        assert(kn->kn_tq == &kq->kq_head);
        TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
        kn->kn_tq = inprocessp;
        TAILQ_INSERT_TAIL(inprocessp, kn, kn_tqe);

        /*
         * Determine how to dispatch the knote for future event handling.
         * not-fired: just return (do not callout).
         * One-shot: deactivate it.
         * Clear: deactivate and clear the state.
         * Dispatch: don't clear state, just deactivate it and mark it disabled.
         * All others: just leave where they are.
         */

        if (result == 0) {
                return EJUSTRETURN;
        } else if ((kn->kn_flags & EV_ONESHOT) != 0) {
                knote_deactivate(kn);
                if (kqlock2knotedrop(kq, kn)) {
                        kn->kn_fop->f_detach(kn);
                        knote_drop(kn, p);
                }
        } else if ((kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) != 0) {
                if ((kn->kn_flags & EV_DISPATCH) != 0) {
                        /* deactivate and disable all dispatch knotes */
                        knote_deactivate(kn);
                        kn->kn_status |= KN_DISABLED;
                } else if (!touch || kn->kn_fflags == 0) {
                        /* only deactivate if nothing since the touch */
                        knote_deactivate(kn);
                }
                if (!touch && (kn->kn_flags & EV_CLEAR) != 0) {
                        /* manually clear non-touch knotes */
                        kn->kn_data = 0;
                        kn->kn_fflags = 0;
                }
                kqunlock(kq);
        } else {
                /*
                 * leave on inprocess queue.  We'll
                 * move all the remaining ones back
                 * the kq queue and wakeup any
                 * waiters when we are done.
                 */
                kqunlock(kq);
        }

        /* callback to handle each event as we find it */
        error = (callback)(kq, &kev, data);
        
        kqlock(kq);
        return error;
}

/*
 * Return 0 to indicate that processing should proceed,
 * -1 if there is nothing to process.
 *
 * Called with kqueue locked and returns the same way,
 * but may drop lock temporarily.
 */
static int
kqueue_begin_processing(struct kqueue *kq)
{
        for (;;) {
                if (kq->kq_count == 0) {
                        return -1;
                }

                /* if someone else is processing the queue, wait */
                if (kq->kq_nprocess != 0) {
                        wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, &kq->kq_nprocess, THREAD_UNINT, 0);
                        kq->kq_state |= KQ_PROCWAIT;
                        kqunlock(kq);
                        thread_block(THREAD_CONTINUE_NULL);
                        kqlock(kq);
                } else {
                        kq->kq_nprocess = 1;
                        return 0;
                }
        }
}

/*
 * Called with kqueue lock held.
 */
static void
kqueue_end_processing(struct kqueue *kq)
{
        kq->kq_nprocess = 0;
        if (kq->kq_state & KQ_PROCWAIT) {
                kq->kq_state &= ~KQ_PROCWAIT;
                wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kq->kq_nprocess, THREAD_AWAKENED);
        }
}

/*
 * kqueue_process - process the triggered events in a kqueue
 *
 *      Walk the queued knotes and validate that they are
 *      really still triggered events by calling the filter
 *      routines (if necessary).  Hold a use reference on
 *      the knote to avoid it being detached. For each event
 *      that is still considered triggered, invoke the
 *      callback routine provided.
 *
 *      caller holds a reference on the kqueue.
 *      kqueue locked on entry and exit - but may be dropped
 *      kqueue list locked (held for duration of call)
 */

static int
kqueue_process(struct kqueue *kq,
               kevent_callback_t callback,
               void *data, 
               int *countp,
               struct proc *p)
{
        struct kqtailq inprocess;
        struct knote *kn;
        int nevents;
        int error;

        TAILQ_INIT(&inprocess);

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

        /*
         * Clear any pre-posted status from previous runs, so we only
         * detect events that occur during this run.
         */
        wait_queue_sub_clearrefs(kq->kq_wqs);

        /*
         * loop through the enqueued knotes, processing each one and
         * revalidating those that need it. As they are processed,
         * they get moved to the inprocess queue (so the loop can end).
         */
        error = 0;
        nevents = 0;

        while (error == 0 &&
               (kn = TAILQ_FIRST(&kq->kq_head)) != NULL) {
                error = knote_process(kn, callback, data, &inprocess, p);
                if (error == EJUSTRETURN)
                        error = 0;
                else
                        nevents++;
        }

        /*
         * With the kqueue still locked, move any knotes
         * remaining on the inprocess queue back to the
         * kq's queue and wake up any waiters.
         */
        while ((kn = TAILQ_FIRST(&inprocess)) != NULL) {
                assert(kn->kn_tq == &inprocess);
                TAILQ_REMOVE(&inprocess, kn, kn_tqe);
                kn->kn_tq = &kq->kq_head;
                TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
        }

        kqueue_end_processing(kq);

        *countp = nevents;
        return error;
}


static void
kqueue_scan_continue(void *data, wait_result_t wait_result)
{
        thread_t self = current_thread();
        uthread_t ut = (uthread_t)get_bsdthread_info(self);
        struct _kqueue_scan * cont_args = &ut->uu_kevent.ss_kqueue_scan;
        struct kqueue *kq = (struct kqueue *)data;
        int error;
        int count;

        /* convert the (previous) wait_result to a proper error */
        switch (wait_result) {
        case THREAD_AWAKENED:
                kqlock(kq);
                error = kqueue_process(kq, cont_args->call, cont_args, &count, current_proc());
                if (error == 0 && count == 0) {
                        wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, KQ_EVENT, 
                                               THREAD_ABORTSAFE, cont_args->deadline); 
                        kq->kq_state |= KQ_SLEEP;
                        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;
        default:
                panic("kevent_scan_cont() - invalid wait_result (%d)", 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 *data,
            struct timeval *atvp,
            struct proc *p)
{
        thread_continue_t cont = THREAD_CONTINUE_NULL;
        uint64_t deadline;
        int error;
        int first;

        assert(callback != NULL);

        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, data, &count, p);
                if (error || count)
                        break; /* lock still held */

                /* looks like we have to consider blocking */
                if (first) {
                        first = 0;
                        /* convert the timeout to a deadline once */
                        if (atvp->tv_sec || atvp->tv_usec) {
                                uint64_t now;
                                
                                clock_get_uptime(&now);
                                nanoseconds_to_absolutetime((uint64_t)atvp->tv_sec * NSEC_PER_SEC +
                                                            atvp->tv_usec * NSEC_PER_USEC,
                                                            &deadline);
                                if (now >= deadline) {
                                        /* non-blocking call */
                                        error = EWOULDBLOCK;
                                        break; /* lock still held */
                                }
                                deadline -= now;
                                clock_absolutetime_interval_to_deadline(deadline, &deadline);
                        } else {
                                deadline = 0;   /* block forever */
                        }

                        if (continuation) {
                                uthread_t ut = (uthread_t)get_bsdthread_info(current_thread());
                                struct _kqueue_scan *cont_args = &ut->uu_kevent.ss_kqueue_scan;
                                
                                cont_args->call = callback;
                                cont_args->cont = continuation;
                                cont_args->deadline = deadline;
                                cont_args->data = data;
                                cont = kqueue_scan_continue;
                        }
                }

                /* go ahead and wait */
                wait_queue_assert_wait((wait_queue_t)kq->kq_wqs, KQ_EVENT, THREAD_ABORTSAFE, deadline);
                kq->kq_state |= KQ_SLEEP;
                kqunlock(kq);
                wait_result = thread_block_parameter(cont, kq);
                /* NOTREACHED if (continuation != NULL) */

                switch (wait_result) {
                case THREAD_AWAKENED:
                        continue;
                case THREAD_TIMED_OUT:
                        return EWOULDBLOCK; 
                case THREAD_INTERRUPTED:
                        return EINTR;
                default:
                        panic("kevent_scan - bad wait_result (%d)",
                              wait_result);
                        error = 0;
                }
        }
        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 *wql, __unused vfs_context_t ctx)
{
        struct kqueue *kq = (struct kqueue *)fp->f_data;
        struct knote *kn;
        struct kqtailq inprocessq;
        int retnum = 0;
        
        if (which != FREAD)
                return 0;

        TAILQ_INIT(&inprocessq);

        kqlock(kq);
        /* 
         * If this is the first pass, link the wait queue associated with the
         * the kqueue onto the wait queue set for the select().  Normally we
         * use selrecord() for this, but it uses the wait queue within the
         * selinfo structure and we need to use the main one for the kqueue to
         * catch events from KN_STAYQUEUED sources. So we do the linkage manually.
         * (The select() call will unlink them when it ends).
         */
        if (wql != NULL) {
                thread_t        cur_act = current_thread();
                struct uthread * ut = get_bsdthread_info(cur_act);

                kq->kq_state |= KQ_SEL;
                wait_queue_link_noalloc((wait_queue_t)kq->kq_wqs, ut->uu_wqset,
                                        (wait_queue_link_t)wql);
        }

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

        if (kq->kq_count != 0) {
                /*
                 * there is something queued - but it might be a
                 * KN_STAYQUEUED knote, which may or may not have
                 * any events pending.  So, we have to walk the
                 * list of knotes to see, and peek at the stay-
                 * queued ones to be really sure.
                 */
                while ((kn = (struct knote*)TAILQ_FIRST(&kq->kq_head)) != NULL) {
                        if ((kn->kn_status & KN_STAYQUEUED) == 0) {
                                retnum = 1;
                                goto out;
                        }

                        TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
                        TAILQ_INSERT_TAIL(&inprocessq, kn, kn_tqe);

                        if (kqlock2knoteuse(kq, kn)) {
                                unsigned peek;

                                peek = kn->kn_fop->f_peek(kn);
                                if (knoteuse2kqlock(kq, kn)) {
                                        if (peek > 0) {
                                                retnum = 1;
                                                goto out;
                                        }
                                } else {
                                        retnum = 0;
                                }
                        } 
                }
        }

out:
        /* Return knotes to active queue */
        while ((kn = TAILQ_FIRST(&inprocessq)) != NULL) {
                TAILQ_REMOVE(&inprocessq, kn, kn_tqe);
                kn->kn_tq = &kq->kq_head;
                TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
        }

        kqueue_end_processing(kq);
        kqunlock(kq);
        return retnum;
}

/*
 * kqueue_close -
 */
/*ARGSUSED*/
static int
kqueue_close(struct fileglob *fg, __unused vfs_context_t ctx)
{
        struct kqueue *kq = (struct kqueue *)fg->fg_data;

        kqueue_dealloc(kq);
        fg->fg_data = NULL;
        return (0);
}

/*ARGSUSED*/
/*
 * The callers has taken a use-count reference on this kqueue and will donate it
 * to the kqueue we are being added to.  This keeps the kqueue from closing until
 * that relationship is torn down.
 */
static int
kqueue_kqfilter(__unused struct fileproc *fp, struct knote *kn, __unused vfs_context_t ctx)
{
        struct kqueue *kq = (struct kqueue *)kn->kn_fp->f_data;
        struct kqueue *parentkq = kn->kn_kq;

        if (parentkq == kq ||
            kn->kn_filter != EVFILT_READ)
                return (1);

        /*
         * We have to avoid creating a cycle when nesting kqueues
         * inside another.  Rather than trying to walk the whole
         * potential DAG of nested kqueues, we just use a simple
         * ceiling protocol.  When a kqueue is inserted into another,
         * we check that the (future) parent is not already nested
         * into another kqueue at a lower level than the potenial
         * child (because it could indicate a cycle).  If that test
         * passes, we just mark the nesting levels accordingly.
         */

        kqlock(parentkq);
        if (parentkq->kq_level > 0 && 
            parentkq->kq_level < kq->kq_level)
        {
                kqunlock(parentkq);
                return (1);
        } else {
                /* set parent level appropriately */
                if (parentkq->kq_level == 0)
                        parentkq->kq_level = 2;
                if (parentkq->kq_level < kq->kq_level + 1)
                        parentkq->kq_level = kq->kq_level + 1;
                kqunlock(parentkq);

                kn->kn_fop = &kqread_filtops;
                kqlock(kq);
                KNOTE_ATTACH(&kq->kq_sel.si_note, kn);
                /* indicate nesting in child, if needed */
                if (kq->kq_level == 0)
                        kq->kq_level = 1;
                kqunlock(kq);
                return (0);
        }
}

/*
 * kqueue_drain - called when kq is closed
 */
/*ARGSUSED*/
static int
kqueue_drain(struct fileproc *fp, __unused vfs_context_t ctx)
{
        struct kqueue *kq = (struct kqueue *)fp->f_fglob->fg_data;
        kqlock(kq);
        kqueue_wakeup(kq, 1);
        kqunlock(kq);
        return 0;
}

/*ARGSUSED*/
int
kqueue_stat(struct fileproc *fp, void *ub, int isstat64,  __unused vfs_context_t ctx)
{

        struct kqueue *kq = (struct kqueue *)fp->f_data;
        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_KEV64)
                        sb64->st_blksize = sizeof(struct kevent64_s);
                else
                        sb64->st_blksize = sizeof(struct kevent);
                sb64->st_mode = S_IFIFO;
        } else {
                struct stat *sb = (struct stat *)ub;

                bzero((void *)sb, sizeof(*sb));
                sb->st_size = kq->kq_count;
                if (kq->kq_state & KQ_KEV64)
                        sb->st_blksize = sizeof(struct kevent64_s);
                else
                        sb->st_blksize = sizeof(struct kevent);
                sb->st_mode = S_IFIFO;
        }

        return (0);
}

/*
 * Called with the kqueue locked
 */
static void
kqueue_wakeup(struct kqueue *kq, int closed)
{
        if ((kq->kq_state & (KQ_SLEEP | KQ_SEL)) != 0 || kq->kq_nprocess > 0) {
                kq->kq_state &= ~(KQ_SLEEP | KQ_SEL);
                wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, KQ_EVENT, 
                                      (closed) ? THREAD_INTERRUPTED : THREAD_AWAKENED);
        }
}

void
klist_init(struct klist *list)
{
        SLIST_INIT(list);
}


/*
 * Query/Post each knote in the object's list
 *
 *      The object lock protects the list. It is assumed
 *      that the filter/event routine for the object can
 *      determine that the object is already locked (via
 *      the hint) and not deadlock itself.
 *
 *      The object lock should also hold off pending
 *      detach/drop operations.  But we'll prevent it here
 *      too - just in case.
 */
void
knote(struct klist *list, long hint)
{
        struct knote *kn;

        SLIST_FOREACH(kn, list, kn_selnext) {
                struct kqueue *kq = kn->kn_kq;

                kqlock(kq);
                if (kqlock2knoteuse(kq, kn)) {
                        int result;

                        /* call the event with only a use count */
                        result = kn->kn_fop->f_event(kn, hint);

                        /* if its not going away and triggered */
                        if (knoteuse2kqlock(kq, kn) && result)
                                knote_activate(kn, 1);
                        /* lock held again */
                }
                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);
}

/*
 * 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.
 */
int
knote_link_wait_queue(struct knote *kn, struct wait_queue *wq)
{
        struct kqueue *kq = kn->kn_kq;
        kern_return_t kr;

        kr = wait_queue_link(wq, kq->kq_wqs);
        if (kr == KERN_SUCCESS) {
                knote_markstayqueued(kn);
                return 0;
        } else {
                return ENOMEM;
        }
}

/*
 * 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.
 */
void
knote_unlink_wait_queue(struct knote *kn, struct wait_queue *wq)
{
        struct kqueue *kq = kn->kn_kq;

        (void) wait_queue_unlink(wq, kq->kq_wqs);
        kqlock(kq);
        kn->kn_status &= ~KN_STAYQUEUED;
        knote_dequeue(kn);
        kqunlock(kq);
}

/*
 * remove all knotes referencing a specified fd
 *
 * Essentially an inlined knote_remove & knote_drop
 * when we know for sure that the thing is a file
 * 
 * Entered with the proc_fd lock already held.
 * It returns the same way, but may drop it temporarily.
 */
void
knote_fdclose(struct proc *p, int fd)
{
        struct filedesc *fdp = p->p_fd;
        struct klist *list;
        struct knote *kn;

        list = &fdp->fd_knlist[fd];
        while ((kn = SLIST_FIRST(list)) != NULL) {
                struct kqueue *kq = kn->kn_kq;

                if (kq->kq_p != p)
                        panic("knote_fdclose: proc mismatch (kq->kq_p=%p != p=%p)", kq->kq_p, p);

                kqlock(kq);
                proc_fdunlock(p);

                /*
                 * Convert the lock to a drop ref.
                 * If we get it, go ahead and drop it.
                 * Otherwise, we waited for it to
                 * be dropped by the other guy, so
                 * it is safe to move on in the list.
                 */
                if (kqlock2knotedrop(kq, kn)) {
                        kn->kn_fop->f_detach(kn);
                        knote_drop(kn, p);
                }
                        
                proc_fdlock(p);

                /* the fd tables may have changed - start over */
                list = &fdp->fd_knlist[fd];
        }
}

/* proc_fdlock held on entry (and exit) */
static int
knote_fdpattach(struct knote *kn, struct filedesc *fdp, __unused struct proc *p)
{
        struct klist *list = NULL;

        if (! kn->kn_fop->f_isfd) {
                if (fdp->fd_knhashmask == 0)
                        fdp->fd_knhash = hashinit(CONFIG_KN_HASHSIZE, M_KQUEUE,
                            &fdp->fd_knhashmask);
                list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
        } else {
                if ((u_int)fdp->fd_knlistsize <= kn->kn_id) {
                        u_int size = 0;

                        /* have to grow the fd_knlist */
                        size = fdp->fd_knlistsize;
                        while (size <= kn->kn_id)
                                size += KQEXTENT;
                        MALLOC(list, struct klist *,
                               size * sizeof(struct klist *), M_KQUEUE, M_WAITOK);
                        if (list == NULL)
                                return (ENOMEM);
                        
                        bcopy((caddr_t)fdp->fd_knlist, (caddr_t)list,
                              fdp->fd_knlistsize * sizeof(struct klist *));
                        bzero((caddr_t)list +
                              fdp->fd_knlistsize * sizeof(struct klist *),
                              (size - fdp->fd_knlistsize) * sizeof(struct klist *));
                        FREE(fdp->fd_knlist, M_KQUEUE);
                        fdp->fd_knlist = list;
                        fdp->fd_knlistsize = size;
                }
                list = &fdp->fd_knlist[kn->kn_id];
        }
        SLIST_INSERT_HEAD(list, kn, kn_link);
        return (0);
}



/*
 * should be called at spl == 0, since we don't want to hold spl
 * while calling fdrop and free.
 */
static void
knote_drop(struct knote *kn, __unused struct proc *ctxp)
{
        struct kqueue *kq = kn->kn_kq;
        struct proc *p = kq->kq_p;
        struct filedesc *fdp = p->p_fd;
        struct klist *list;
        int needswakeup;

        proc_fdlock(p);
        if (kn->kn_fop->f_isfd)
                list = &fdp->fd_knlist[kn->kn_id];
        else
                list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];

        SLIST_REMOVE(list, kn, knote, kn_link);
        kqlock(kq);
        knote_dequeue(kn);
        needswakeup = (kn->kn_status & KN_USEWAIT);
        kqunlock(kq);
        proc_fdunlock(p);

        if (needswakeup)
                wait_queue_wakeup_all((wait_queue_t)kq->kq_wqs, &kn->kn_status, THREAD_AWAKENED);

        if (kn->kn_fop->f_isfd)
                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, int propagate)
{
        struct kqueue *kq = kn->kn_kq;

        kn->kn_status |= KN_ACTIVE;
        knote_enqueue(kn);
        kqueue_wakeup(kq, 0);

        /* this is a real event: wake up the parent kq, too */
        if (propagate)
                KNOTE(&kq->kq_sel.si_note, 0);
}

/* called with kqueue lock held */
static void
knote_deactivate(struct knote *kn)
{       
        kn->kn_status &= ~KN_ACTIVE;
        knote_dequeue(kn);
}

/* called with kqueue lock held */
static void
knote_enqueue(struct knote *kn)
{
        if ((kn->kn_status & (KN_QUEUED | KN_STAYQUEUED)) == KN_STAYQUEUED ||
            (kn->kn_status & (KN_QUEUED | KN_STAYQUEUED | KN_DISABLED)) == 0) {
                struct kqtailq *tq = kn->kn_tq;
                struct kqueue *kq = kn->kn_kq;

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

/* called with kqueue lock held */
static void
knote_dequeue(struct knote *kn)
{
        struct kqueue *kq = kn->kn_kq;

        if ((kn->kn_status & (KN_QUEUED | KN_STAYQUEUED)) == KN_QUEUED) {
                struct kqtailq *tq = kn->kn_tq;

                TAILQ_REMOVE(tq, kn, kn_tqe); 
                kn->kn_tq = &kq->kq_head;
                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");

        /* allocate kq lock group attribute and group */
        kq_lck_grp_attr= lck_grp_attr_alloc_init();

        kq_lck_grp = lck_grp_alloc_init("kqueue",  kq_lck_grp_attr);

        /* Allocate kq lock attribute */
        kq_lck_attr = lck_attr_alloc_init();

        /* Initialize the timer filter lock */
        lck_mtx_init(&_filt_timerlock, kq_lck_grp, kq_lck_attr);
        lck_mtx_init(&vm_pressure_klist_mutex, kq_lck_grp, kq_lck_attr);
}
SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_ANY, knote_init, NULL)

static struct knote *
knote_alloc(void)
{
        return ((struct knote *)zalloc(knote_zone));
}

static void
knote_free(struct knote *kn)
{
        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>


static int kev_attach(struct socket *so, int proto, struct proc *p);
static int kev_detach(struct socket *so);
static int kev_control(struct socket *so, u_long cmd, caddr_t data, struct ifnet *ifp, struct proc *p);

struct pr_usrreqs event_usrreqs = {
     pru_abort_notsupp, pru_accept_notsupp, kev_attach, pru_bind_notsupp, pru_connect_notsupp,
     pru_connect2_notsupp, kev_control, kev_detach, pru_disconnect_notsupp,
     pru_listen_notsupp, pru_peeraddr_notsupp, pru_rcvd_notsupp, pru_rcvoob_notsupp,
     pru_send_notsupp, pru_sense_null, pru_shutdown_notsupp, pru_sockaddr_notsupp,
     pru_sosend_notsupp, soreceive, pru_sopoll_notsupp
};

struct protosw eventsw[] = {
     {
          .pr_type = SOCK_RAW,
          .pr_domain = &systemdomain,
          .pr_protocol = SYSPROTO_EVENT,
          .pr_flags = PR_ATOMIC,
          .pr_usrreqs = &event_usrreqs,
     }
};

static
struct kern_event_head kern_event_head;

static u_int32_t static_event_id = 0;
struct domain *sysdom = &systemdomain;
static lck_mtx_t *sys_mtx;

/*
 * Install the protosw's for the NKE manager.  Invoked at
 *  extension load time
 */
int
kern_event_init(void)
{
    int retval;

    if ((retval = net_add_proto(eventsw, &systemdomain)) != 0) {
            log(LOG_WARNING, "Can't install kernel events protocol (%d)\n", retval);
            return(retval);
        }
   
    /*
     * Use the domain mutex for all system event sockets
     */ 
    sys_mtx = sysdom->dom_mtx;
        
    return(KERN_SUCCESS);
}

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

     error = soreserve(so, KEV_SNDSPACE, KEV_RECVSPACE);
     if (error)
          return error;

     MALLOC(ev_pcb, struct kern_event_pcb *, sizeof(struct kern_event_pcb), M_PCB, M_WAITOK);
     if (ev_pcb == 0)
          return ENOBUFS;

     ev_pcb->ev_socket = so;
     ev_pcb->vendor_code_filter = 0xffffffff;

     so->so_pcb = (caddr_t) ev_pcb;
     lck_mtx_lock(sys_mtx);
     LIST_INSERT_HEAD(&kern_event_head, ev_pcb, ev_link);
     lck_mtx_unlock(sys_mtx);

     return 0;
}


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

     if (ev_pcb != 0) {
                LIST_REMOVE(ev_pcb, ev_link);
                FREE(ev_pcb, M_PCB);
                so->so_pcb = 0;
                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)
        {
                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) {
                return EMSGSIZE;
        }

     m = m_get(M_DONTWAIT, MT_DATA);
     if (m == 0)
          return ENOBUFS;

     ev = mtod(m, struct kern_event_msg *);
     total_size = KEV_MSG_HEADER_SIZE;

     tmp = (char *) &ev->event_data[0];
     for (i = 0; i < 5; i++) {
          if (event_msg->dv[i].data_length == 0)
               break;

          total_size += event_msg->dv[i].data_length;
          bcopy(event_msg->dv[i].data_ptr, tmp, 
                event_msg->dv[i].data_length);
          tmp += event_msg->dv[i].data_length;
     }

     ev->id = ++static_event_id;
     ev->total_size   = total_size;
     ev->vendor_code  = event_msg->vendor_code;
     ev->kev_class    = event_msg->kev_class;
     ev->kev_subclass = event_msg->kev_subclass;
     ev->event_code   = event_msg->event_code;

     m->m_len = total_size;
     lck_mtx_lock(sys_mtx);
     for (ev_pcb = LIST_FIRST(&kern_event_head); 
          ev_pcb; 
          ev_pcb = LIST_NEXT(ev_pcb, ev_link)) {

          if (ev_pcb->vendor_code_filter != KEV_ANY_VENDOR) {
               if (ev_pcb->vendor_code_filter != ev->vendor_code)
                    continue;

               if (ev_pcb->class_filter != KEV_ANY_CLASS) {
                    if (ev_pcb->class_filter != ev->kev_class)
                         continue;

                    if ((ev_pcb->subclass_filter != KEV_ANY_SUBCLASS) &&
                        (ev_pcb->subclass_filter != ev->kev_subclass))
                         continue;
               }
          }

          m2 = m_copym(m, 0, m->m_len, M_NOWAIT);
          if (m2 == 0) {
               m_free(m);
                   lck_mtx_unlock(sys_mtx);
               return ENOBUFS;
          }
          /* the socket is already locked because we hold the sys_mtx here */
          if (sbappendrecord(&ev_pcb->ev_socket->so_rcv, m2))
                  sorwakeup(ev_pcb->ev_socket);
     }

     m_free(m);
     lck_mtx_unlock(sys_mtx);
     return 0;
}

static int
kev_control(struct socket *so, 
                        u_long cmd, 
                        caddr_t data, 
                        __unused struct ifnet *ifp, 
                        __unused struct proc *p)
{
        struct kev_request *kev_req = (struct kev_request *) data;
        struct kern_event_pcb  *ev_pcb;
        struct kev_vendor_code *kev_vendor;
        u_int32_t  *id_value = (u_int32_t *) data;
        
        
        switch (cmd) {
                
                case SIOCGKEVID:
                        *id_value = static_event_id;
                        break;
                
                case SIOCSKEVFILT:
                        ev_pcb = (struct kern_event_pcb *) so->so_pcb;
                        ev_pcb->vendor_code_filter = kev_req->vendor_code;
                        ev_pcb->class_filter     = kev_req->kev_class;
                        ev_pcb->subclass_filter  = kev_req->kev_subclass;
                        break;
                
                case SIOCGKEVFILT:
                        ev_pcb = (struct kern_event_pcb *) so->so_pcb;
                        kev_req->vendor_code = ev_pcb->vendor_code_filter;
                        kev_req->kev_class   = ev_pcb->class_filter;
                        kev_req->kev_subclass = ev_pcb->subclass_filter;
                        break;
                
                case SIOCGKEVVENDOR:
                        kev_vendor = (struct kev_vendor_code*)data;
                        
                        /* Make sure string is NULL terminated */
                        kev_vendor->vendor_string[KEV_VENDOR_CODE_MAX_STR_LEN-1] = 0;
                
                        return net_str_id_find_internal(kev_vendor->vendor_string, 
                                        &kev_vendor->vendor_code, NSI_VENDOR_CODE, 0);
                
                default:
                        return ENOTSUP;
        }
        
        return 0;
}

#endif /* SOCKETS */


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

        /* No need for the funnel as fd is kept alive */
        
        st = &kinfo->kq_stat;

        st->vst_size = kq->kq_count;
        if (kq->kq_state & KQ_KEV64)
                st->vst_blksize = sizeof(struct kevent64_s);
        else
                st->vst_blksize = sizeof(struct kevent);
        st->vst_mode = S_IFIFO;
        if (kq->kq_state & KQ_SEL)
                kinfo->kq_state |=  PROC_KQUEUE_SELECT;
        if (kq->kq_state & KQ_SLEEP)
                kinfo->kq_state |= PROC_KQUEUE_SLEEP;

        return(0);
}


void
knote_markstayqueued(struct knote *kn)
{
        kqlock(kn->kn_kq);
        kn->kn_status |= KN_STAYQUEUED;
        knote_enqueue(kn);
        kqunlock(kn->kn_kq);
}