The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_event.c

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    1 /*-
    2  * Copyright (c) 1999,2000,2001 Jonathan Lemon <jlemon@FreeBSD.org>
    3  * Copyright 2004 John-Mark Gurney <jmg@FreeBSD.org>
    4  * Copyright (c) 2009 Apple, Inc.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: stable/10/sys/kern/kern_event.c 320293 2017-06-23 19:04:40Z kib $");
   31 
   32 #include "opt_ktrace.h"
   33 
   34 #include <sys/param.h>
   35 #include <sys/systm.h>
   36 #include <sys/capsicum.h>
   37 #include <sys/kernel.h>
   38 #include <sys/lock.h>
   39 #include <sys/mutex.h>
   40 #include <sys/rwlock.h>
   41 #include <sys/proc.h>
   42 #include <sys/malloc.h>
   43 #include <sys/unistd.h>
   44 #include <sys/file.h>
   45 #include <sys/filedesc.h>
   46 #include <sys/filio.h>
   47 #include <sys/fcntl.h>
   48 #include <sys/kthread.h>
   49 #include <sys/selinfo.h>
   50 #include <sys/queue.h>
   51 #include <sys/event.h>
   52 #include <sys/eventvar.h>
   53 #include <sys/poll.h>
   54 #include <sys/protosw.h>
   55 #include <sys/sigio.h>
   56 #include <sys/signalvar.h>
   57 #include <sys/socket.h>
   58 #include <sys/socketvar.h>
   59 #include <sys/stat.h>
   60 #include <sys/sysctl.h>
   61 #include <sys/sysproto.h>
   62 #include <sys/syscallsubr.h>
   63 #include <sys/taskqueue.h>
   64 #include <sys/uio.h>
   65 #ifdef KTRACE
   66 #include <sys/ktrace.h>
   67 #endif
   68 #include <machine/atomic.h>
   69 
   70 #include <vm/uma.h>
   71 
   72 static MALLOC_DEFINE(M_KQUEUE, "kqueue", "memory for kqueue system");
   73 
   74 /*
   75  * This lock is used if multiple kq locks are required.  This possibly
   76  * should be made into a per proc lock.
   77  */
   78 static struct mtx       kq_global;
   79 MTX_SYSINIT(kq_global, &kq_global, "kqueue order", MTX_DEF);
   80 #define KQ_GLOBAL_LOCK(lck, haslck)     do {    \
   81         if (!haslck)                            \
   82                 mtx_lock(lck);                  \
   83         haslck = 1;                             \
   84 } while (0)
   85 #define KQ_GLOBAL_UNLOCK(lck, haslck)   do {    \
   86         if (haslck)                             \
   87                 mtx_unlock(lck);                        \
   88         haslck = 0;                             \
   89 } while (0)
   90 
   91 TASKQUEUE_DEFINE_THREAD(kqueue);
   92 
   93 static int      kevent_copyout(void *arg, struct kevent *kevp, int count);
   94 static int      kevent_copyin(void *arg, struct kevent *kevp, int count);
   95 static int      kqueue_register(struct kqueue *kq, struct kevent *kev,
   96                     struct thread *td, int waitok);
   97 static int      kqueue_acquire(struct file *fp, struct kqueue **kqp);
   98 static void     kqueue_release(struct kqueue *kq, int locked);
   99 static int      kqueue_expand(struct kqueue *kq, struct filterops *fops,
  100                     uintptr_t ident, int waitok);
  101 static void     kqueue_task(void *arg, int pending);
  102 static int      kqueue_scan(struct kqueue *kq, int maxevents,
  103                     struct kevent_copyops *k_ops,
  104                     const struct timespec *timeout,
  105                     struct kevent *keva, struct thread *td);
  106 static void     kqueue_wakeup(struct kqueue *kq);
  107 static struct filterops *kqueue_fo_find(int filt);
  108 static void     kqueue_fo_release(int filt);
  109 
  110 static fo_rdwr_t        kqueue_read;
  111 static fo_rdwr_t        kqueue_write;
  112 static fo_truncate_t    kqueue_truncate;
  113 static fo_ioctl_t       kqueue_ioctl;
  114 static fo_poll_t        kqueue_poll;
  115 static fo_kqfilter_t    kqueue_kqfilter;
  116 static fo_stat_t        kqueue_stat;
  117 static fo_close_t       kqueue_close;
  118 
  119 static struct fileops kqueueops = {
  120         .fo_read = kqueue_read,
  121         .fo_write = kqueue_write,
  122         .fo_truncate = kqueue_truncate,
  123         .fo_ioctl = kqueue_ioctl,
  124         .fo_poll = kqueue_poll,
  125         .fo_kqfilter = kqueue_kqfilter,
  126         .fo_stat = kqueue_stat,
  127         .fo_close = kqueue_close,
  128         .fo_chmod = invfo_chmod,
  129         .fo_chown = invfo_chown,
  130         .fo_sendfile = invfo_sendfile,
  131 };
  132 
  133 static int      knote_attach(struct knote *kn, struct kqueue *kq);
  134 static void     knote_drop(struct knote *kn, struct thread *td);
  135 static void     knote_enqueue(struct knote *kn);
  136 static void     knote_dequeue(struct knote *kn);
  137 static void     knote_init(void);
  138 static struct   knote *knote_alloc(int waitok);
  139 static void     knote_free(struct knote *kn);
  140 
  141 static void     filt_kqdetach(struct knote *kn);
  142 static int      filt_kqueue(struct knote *kn, long hint);
  143 static int      filt_procattach(struct knote *kn);
  144 static void     filt_procdetach(struct knote *kn);
  145 static int      filt_proc(struct knote *kn, long hint);
  146 static int      filt_fileattach(struct knote *kn);
  147 static void     filt_timerexpire(void *knx);
  148 static int      filt_timerattach(struct knote *kn);
  149 static void     filt_timerdetach(struct knote *kn);
  150 static int      filt_timer(struct knote *kn, long hint);
  151 static int      filt_userattach(struct knote *kn);
  152 static void     filt_userdetach(struct knote *kn);
  153 static int      filt_user(struct knote *kn, long hint);
  154 static void     filt_usertouch(struct knote *kn, struct kevent *kev,
  155                     u_long type);
  156 
  157 static struct filterops file_filtops = {
  158         .f_isfd = 1,
  159         .f_attach = filt_fileattach,
  160 };
  161 static struct filterops kqread_filtops = {
  162         .f_isfd = 1,
  163         .f_detach = filt_kqdetach,
  164         .f_event = filt_kqueue,
  165 };
  166 /* XXX - move to kern_proc.c?  */
  167 static struct filterops proc_filtops = {
  168         .f_isfd = 0,
  169         .f_attach = filt_procattach,
  170         .f_detach = filt_procdetach,
  171         .f_event = filt_proc,
  172 };
  173 static struct filterops timer_filtops = {
  174         .f_isfd = 0,
  175         .f_attach = filt_timerattach,
  176         .f_detach = filt_timerdetach,
  177         .f_event = filt_timer,
  178 };
  179 static struct filterops user_filtops = {
  180         .f_attach = filt_userattach,
  181         .f_detach = filt_userdetach,
  182         .f_event = filt_user,
  183         .f_touch = filt_usertouch,
  184 };
  185 
  186 static uma_zone_t       knote_zone;
  187 static unsigned int     kq_ncallouts = 0;
  188 static unsigned int     kq_calloutmax = 4 * 1024;
  189 SYSCTL_UINT(_kern, OID_AUTO, kq_calloutmax, CTLFLAG_RW,
  190     &kq_calloutmax, 0, "Maximum number of callouts allocated for kqueue");
  191 
  192 /* XXX - ensure not KN_INFLUX?? */
  193 #define KNOTE_ACTIVATE(kn, islock) do {                                 \
  194         if ((islock))                                                   \
  195                 mtx_assert(&(kn)->kn_kq->kq_lock, MA_OWNED);            \
  196         else                                                            \
  197                 KQ_LOCK((kn)->kn_kq);                                   \
  198         (kn)->kn_status |= KN_ACTIVE;                                   \
  199         if (((kn)->kn_status & (KN_QUEUED | KN_DISABLED)) == 0)         \
  200                 knote_enqueue((kn));                                    \
  201         if (!(islock))                                                  \
  202                 KQ_UNLOCK((kn)->kn_kq);                                 \
  203 } while(0)
  204 #define KQ_LOCK(kq) do {                                                \
  205         mtx_lock(&(kq)->kq_lock);                                       \
  206 } while (0)
  207 #define KQ_FLUX_WAKEUP(kq) do {                                         \
  208         if (((kq)->kq_state & KQ_FLUXWAIT) == KQ_FLUXWAIT) {            \
  209                 (kq)->kq_state &= ~KQ_FLUXWAIT;                         \
  210                 wakeup((kq));                                           \
  211         }                                                               \
  212 } while (0)
  213 #define KQ_UNLOCK_FLUX(kq) do {                                         \
  214         KQ_FLUX_WAKEUP(kq);                                             \
  215         mtx_unlock(&(kq)->kq_lock);                                     \
  216 } while (0)
  217 #define KQ_UNLOCK(kq) do {                                              \
  218         mtx_unlock(&(kq)->kq_lock);                                     \
  219 } while (0)
  220 #define KQ_OWNED(kq) do {                                               \
  221         mtx_assert(&(kq)->kq_lock, MA_OWNED);                           \
  222 } while (0)
  223 #define KQ_NOTOWNED(kq) do {                                            \
  224         mtx_assert(&(kq)->kq_lock, MA_NOTOWNED);                        \
  225 } while (0)
  226 #define KN_LIST_LOCK(kn) do {                                           \
  227         if (kn->kn_knlist != NULL)                                      \
  228                 kn->kn_knlist->kl_lock(kn->kn_knlist->kl_lockarg);      \
  229 } while (0)
  230 #define KN_LIST_UNLOCK(kn) do {                                         \
  231         if (kn->kn_knlist != NULL)                                      \
  232                 kn->kn_knlist->kl_unlock(kn->kn_knlist->kl_lockarg);    \
  233 } while (0)
  234 #define KNL_ASSERT_LOCK(knl, islocked) do {                             \
  235         if (islocked)                                                   \
  236                 KNL_ASSERT_LOCKED(knl);                         \
  237         else                                                            \
  238                 KNL_ASSERT_UNLOCKED(knl);                               \
  239 } while (0)
  240 #ifdef INVARIANTS
  241 #define KNL_ASSERT_LOCKED(knl) do {                                     \
  242         knl->kl_assert_locked((knl)->kl_lockarg);                       \
  243 } while (0)
  244 #define KNL_ASSERT_UNLOCKED(knl) do {                                   \
  245         knl->kl_assert_unlocked((knl)->kl_lockarg);                     \
  246 } while (0)
  247 #else /* !INVARIANTS */
  248 #define KNL_ASSERT_LOCKED(knl) do {} while(0)
  249 #define KNL_ASSERT_UNLOCKED(knl) do {} while (0)
  250 #endif /* INVARIANTS */
  251 
  252 #define KN_HASHSIZE             64              /* XXX should be tunable */
  253 #define KN_HASH(val, mask)      (((val) ^ (val >> 8)) & (mask))
  254 
  255 static int
  256 filt_nullattach(struct knote *kn)
  257 {
  258 
  259         return (ENXIO);
  260 };
  261 
  262 struct filterops null_filtops = {
  263         .f_isfd = 0,
  264         .f_attach = filt_nullattach,
  265 };
  266 
  267 /* XXX - make SYSINIT to add these, and move into respective modules. */
  268 extern struct filterops sig_filtops;
  269 extern struct filterops fs_filtops;
  270 
  271 /*
  272  * Table for for all system-defined filters.
  273  */
  274 static struct mtx       filterops_lock;
  275 MTX_SYSINIT(kqueue_filterops, &filterops_lock, "protect sysfilt_ops",
  276         MTX_DEF);
  277 static struct {
  278         struct filterops *for_fop;
  279         int for_refcnt;
  280 } sysfilt_ops[EVFILT_SYSCOUNT] = {
  281         { &file_filtops },                      /* EVFILT_READ */
  282         { &file_filtops },                      /* EVFILT_WRITE */
  283         { &null_filtops },                      /* EVFILT_AIO */
  284         { &file_filtops },                      /* EVFILT_VNODE */
  285         { &proc_filtops },                      /* EVFILT_PROC */
  286         { &sig_filtops },                       /* EVFILT_SIGNAL */
  287         { &timer_filtops },                     /* EVFILT_TIMER */
  288         { &null_filtops },                      /* former EVFILT_NETDEV */
  289         { &fs_filtops },                        /* EVFILT_FS */
  290         { &null_filtops },                      /* EVFILT_LIO */
  291         { &user_filtops },                      /* EVFILT_USER */
  292 };
  293 
  294 /*
  295  * Simple redirection for all cdevsw style objects to call their fo_kqfilter
  296  * method.
  297  */
  298 static int
  299 filt_fileattach(struct knote *kn)
  300 {
  301 
  302         return (fo_kqfilter(kn->kn_fp, kn));
  303 }
  304 
  305 /*ARGSUSED*/
  306 static int
  307 kqueue_kqfilter(struct file *fp, struct knote *kn)
  308 {
  309         struct kqueue *kq = kn->kn_fp->f_data;
  310 
  311         if (kn->kn_filter != EVFILT_READ)
  312                 return (EINVAL);
  313 
  314         kn->kn_status |= KN_KQUEUE;
  315         kn->kn_fop = &kqread_filtops;
  316         knlist_add(&kq->kq_sel.si_note, kn, 0);
  317 
  318         return (0);
  319 }
  320 
  321 static void
  322 filt_kqdetach(struct knote *kn)
  323 {
  324         struct kqueue *kq = kn->kn_fp->f_data;
  325 
  326         knlist_remove(&kq->kq_sel.si_note, kn, 0);
  327 }
  328 
  329 /*ARGSUSED*/
  330 static int
  331 filt_kqueue(struct knote *kn, long hint)
  332 {
  333         struct kqueue *kq = kn->kn_fp->f_data;
  334 
  335         kn->kn_data = kq->kq_count;
  336         return (kn->kn_data > 0);
  337 }
  338 
  339 /* XXX - move to kern_proc.c?  */
  340 static int
  341 filt_procattach(struct knote *kn)
  342 {
  343         struct proc *p;
  344         int immediate;
  345         int error;
  346 
  347         immediate = 0;
  348         p = pfind(kn->kn_id);
  349         if (p == NULL && (kn->kn_sfflags & NOTE_EXIT)) {
  350                 p = zpfind(kn->kn_id);
  351                 immediate = 1;
  352         } else if (p != NULL && (p->p_flag & P_WEXIT)) {
  353                 immediate = 1;
  354         }
  355 
  356         if (p == NULL)
  357                 return (ESRCH);
  358         if ((error = p_cansee(curthread, p))) {
  359                 PROC_UNLOCK(p);
  360                 return (error);
  361         }
  362 
  363         kn->kn_ptr.p_proc = p;
  364         kn->kn_flags |= EV_CLEAR;               /* automatically set */
  365 
  366         /*
  367          * Internal flag indicating registration done by kernel for the
  368          * purposes of getting a NOTE_CHILD notification.
  369          */
  370         if (kn->kn_flags & EV_FLAG2) {
  371                 kn->kn_flags &= ~EV_FLAG2;
  372                 kn->kn_data = kn->kn_sdata;             /* ppid */
  373                 kn->kn_fflags = NOTE_CHILD;
  374                 kn->kn_sfflags &= ~NOTE_EXIT;
  375                 immediate = 1; /* Force immediate activation of child note. */
  376         }
  377         /*
  378          * Internal flag indicating registration done by kernel (for other than
  379          * NOTE_CHILD).
  380          */
  381         if (kn->kn_flags & EV_FLAG1) {
  382                 kn->kn_flags &= ~EV_FLAG1;
  383         }
  384 
  385         if (immediate == 0)
  386                 knlist_add(&p->p_klist, kn, 1);
  387 
  388         /*
  389          * Immediately activate any child notes or, in the case of a zombie
  390          * target process, exit notes.  The latter is necessary to handle the
  391          * case where the target process, e.g. a child, dies before the kevent
  392          * is registered.
  393          */
  394         if (immediate && filt_proc(kn, NOTE_EXIT))
  395                 KNOTE_ACTIVATE(kn, 0);
  396 
  397         PROC_UNLOCK(p);
  398 
  399         return (0);
  400 }
  401 
  402 /*
  403  * The knote may be attached to a different process, which may exit,
  404  * leaving nothing for the knote to be attached to.  So when the process
  405  * exits, the knote is marked as DETACHED and also flagged as ONESHOT so
  406  * it will be deleted when read out.  However, as part of the knote deletion,
  407  * this routine is called, so a check is needed to avoid actually performing
  408  * a detach, because the original process does not exist any more.
  409  */
  410 /* XXX - move to kern_proc.c?  */
  411 static void
  412 filt_procdetach(struct knote *kn)
  413 {
  414         struct proc *p;
  415 
  416         p = kn->kn_ptr.p_proc;
  417         knlist_remove(&p->p_klist, kn, 0);
  418         kn->kn_ptr.p_proc = NULL;
  419 }
  420 
  421 /* XXX - move to kern_proc.c?  */
  422 static int
  423 filt_proc(struct knote *kn, long hint)
  424 {
  425         struct proc *p = kn->kn_ptr.p_proc;
  426         u_int event;
  427 
  428         /*
  429          * mask off extra data
  430          */
  431         event = (u_int)hint & NOTE_PCTRLMASK;
  432 
  433         /*
  434          * if the user is interested in this event, record it.
  435          */
  436         if (kn->kn_sfflags & event)
  437                 kn->kn_fflags |= event;
  438 
  439         /*
  440          * process is gone, so flag the event as finished.
  441          */
  442         if (event == NOTE_EXIT) {
  443                 if (!(kn->kn_status & KN_DETACHED))
  444                         knlist_remove_inevent(&p->p_klist, kn);
  445                 kn->kn_flags |= (EV_EOF | EV_ONESHOT);
  446                 kn->kn_ptr.p_proc = NULL;
  447                 if (kn->kn_fflags & NOTE_EXIT)
  448                         kn->kn_data = p->p_xstat;
  449                 if (kn->kn_fflags == 0)
  450                         kn->kn_flags |= EV_DROP;
  451                 return (1);
  452         }
  453 
  454         return (kn->kn_fflags != 0);
  455 }
  456 
  457 /*
  458  * Called when the process forked. It mostly does the same as the
  459  * knote(), activating all knotes registered to be activated when the
  460  * process forked. Additionally, for each knote attached to the
  461  * parent, check whether user wants to track the new process. If so
  462  * attach a new knote to it, and immediately report an event with the
  463  * child's pid.
  464  */
  465 void
  466 knote_fork(struct knlist *list, int pid)
  467 {
  468         struct kqueue *kq;
  469         struct knote *kn;
  470         struct kevent kev;
  471         int error;
  472 
  473         if (list == NULL)
  474                 return;
  475         list->kl_lock(list->kl_lockarg);
  476 
  477         SLIST_FOREACH(kn, &list->kl_list, kn_selnext) {
  478                 if ((kn->kn_status & KN_INFLUX) == KN_INFLUX)
  479                         continue;
  480                 kq = kn->kn_kq;
  481                 KQ_LOCK(kq);
  482                 if ((kn->kn_status & (KN_INFLUX | KN_SCAN)) == KN_INFLUX) {
  483                         KQ_UNLOCK(kq);
  484                         continue;
  485                 }
  486 
  487                 /*
  488                  * The same as knote(), activate the event.
  489                  */
  490                 if ((kn->kn_sfflags & NOTE_TRACK) == 0) {
  491                         kn->kn_status |= KN_HASKQLOCK;
  492                         if (kn->kn_fop->f_event(kn, NOTE_FORK))
  493                                 KNOTE_ACTIVATE(kn, 1);
  494                         kn->kn_status &= ~KN_HASKQLOCK;
  495                         KQ_UNLOCK(kq);
  496                         continue;
  497                 }
  498 
  499                 /*
  500                  * The NOTE_TRACK case. In addition to the activation
  501                  * of the event, we need to register new events to
  502                  * track the child. Drop the locks in preparation for
  503                  * the call to kqueue_register().
  504                  */
  505                 kn->kn_status |= KN_INFLUX;
  506                 KQ_UNLOCK(kq);
  507                 list->kl_unlock(list->kl_lockarg);
  508 
  509                 /*
  510                  * Activate existing knote and register tracking knotes with
  511                  * new process.
  512                  *
  513                  * First register a knote to get just the child notice. This
  514                  * must be a separate note from a potential NOTE_EXIT
  515                  * notification since both NOTE_CHILD and NOTE_EXIT are defined
  516                  * to use the data field (in conflicting ways).
  517                  */
  518                 kev.ident = pid;
  519                 kev.filter = kn->kn_filter;
  520                 kev.flags = kn->kn_flags | EV_ADD | EV_ENABLE | EV_ONESHOT | EV_FLAG2;
  521                 kev.fflags = kn->kn_sfflags;
  522                 kev.data = kn->kn_id;           /* parent */
  523                 kev.udata = kn->kn_kevent.udata;/* preserve udata */
  524                 error = kqueue_register(kq, &kev, NULL, 0);
  525                 if (error)
  526                         kn->kn_fflags |= NOTE_TRACKERR;
  527 
  528                 /*
  529                  * Then register another knote to track other potential events
  530                  * from the new process.
  531                  */
  532                 kev.ident = pid;
  533                 kev.filter = kn->kn_filter;
  534                 kev.flags = kn->kn_flags | EV_ADD | EV_ENABLE | EV_FLAG1;
  535                 kev.fflags = kn->kn_sfflags;
  536                 kev.data = kn->kn_id;           /* parent */
  537                 kev.udata = kn->kn_kevent.udata;/* preserve udata */
  538                 error = kqueue_register(kq, &kev, NULL, 0);
  539                 if (error)
  540                         kn->kn_fflags |= NOTE_TRACKERR;
  541                 if (kn->kn_fop->f_event(kn, NOTE_FORK))
  542                         KNOTE_ACTIVATE(kn, 0);
  543                 KQ_LOCK(kq);
  544                 kn->kn_status &= ~KN_INFLUX;
  545                 KQ_UNLOCK_FLUX(kq);
  546                 list->kl_lock(list->kl_lockarg);
  547         }
  548         list->kl_unlock(list->kl_lockarg);
  549 }
  550 
  551 /*
  552  * XXX: EVFILT_TIMER should perhaps live in kern_time.c beside the
  553  * interval timer support code.
  554  */
  555 
  556 #define NOTE_TIMER_PRECMASK                                             \
  557     (NOTE_SECONDS | NOTE_MSECONDS | NOTE_USECONDS | NOTE_NSECONDS)
  558 
  559 static sbintime_t
  560 timer2sbintime(intptr_t data, int flags)
  561 {
  562         int64_t secs;
  563 
  564         /*
  565          * Macros for converting to the fractional second portion of an
  566          * sbintime_t using 64bit multiplication to improve precision.
  567          */
  568 #define NS_TO_SBT(ns) (((ns) * (((uint64_t)1 << 63) / 500000000)) >> 32)
  569 #define US_TO_SBT(us) (((us) * (((uint64_t)1 << 63) / 500000)) >> 32)
  570 #define MS_TO_SBT(ms) (((ms) * (((uint64_t)1 << 63) / 500)) >> 32)
  571         switch (flags & NOTE_TIMER_PRECMASK) {
  572         case NOTE_SECONDS:
  573 #ifdef __LP64__
  574                 if (data > (SBT_MAX / SBT_1S))
  575                         return (SBT_MAX);
  576 #endif
  577                 return ((sbintime_t)data << 32);
  578         case NOTE_MSECONDS: /* FALLTHROUGH */
  579         case 0:
  580                 if (data >= 1000) {
  581                         secs = data / 1000;
  582 #ifdef __LP64__
  583                         if (secs > (SBT_MAX / SBT_1S))
  584                                 return (SBT_MAX);
  585 #endif
  586                         return (secs << 32 | MS_TO_SBT(data % 1000));
  587                 }
  588                 return (MS_TO_SBT(data));
  589         case NOTE_USECONDS:
  590                 if (data >= 1000000) {
  591                         secs = data / 1000000;
  592 #ifdef __LP64__
  593                         if (secs > (SBT_MAX / SBT_1S))
  594                                 return (SBT_MAX);
  595 #endif
  596                         return (secs << 32 | US_TO_SBT(data % 1000000));
  597                 }
  598                 return (US_TO_SBT(data));
  599         case NOTE_NSECONDS:
  600                 if (data >= 1000000000) {
  601                         secs = data / 1000000000;
  602 #ifdef __LP64__
  603                         if (secs > (SBT_MAX / SBT_1S))
  604                                 return (SBT_MAX);
  605 #endif
  606                         return (secs << 32 | US_TO_SBT(data % 1000000000));
  607                 }
  608                 return (NS_TO_SBT(data));
  609         default:
  610                 break;
  611         }
  612         return (-1);
  613 }
  614 
  615 struct kq_timer_cb_data {
  616         struct callout c;
  617         sbintime_t next;        /* next timer event fires at */
  618         sbintime_t to;          /* precalculated timer period */
  619 };
  620 
  621 static void
  622 filt_timerexpire(void *knx)
  623 {
  624         struct knote *kn;
  625         struct kq_timer_cb_data *kc;
  626 
  627         kn = knx;
  628         kn->kn_data++;
  629         KNOTE_ACTIVATE(kn, 0);  /* XXX - handle locking */
  630 
  631         if ((kn->kn_flags & EV_ONESHOT) != 0)
  632                 return;
  633 
  634         kc = kn->kn_ptr.p_v;
  635         kc->next += kc->to;
  636         callout_reset_sbt_on(&kc->c, kc->next, 0, filt_timerexpire, kn,
  637             PCPU_GET(cpuid), C_ABSOLUTE);
  638 }
  639 
  640 /*
  641  * data contains amount of time to sleep
  642  */
  643 static int
  644 filt_timerattach(struct knote *kn)
  645 {
  646         struct kq_timer_cb_data *kc;
  647         sbintime_t to;
  648         unsigned int ncallouts;
  649 
  650         if (kn->kn_sdata < 0)
  651                 return (EINVAL);
  652         if (kn->kn_sdata == 0 && (kn->kn_flags & EV_ONESHOT) == 0)
  653                 kn->kn_sdata = 1;
  654         /* Only precision unit are supported in flags so far */
  655         if ((kn->kn_sfflags & ~NOTE_TIMER_PRECMASK) != 0)
  656                 return (EINVAL);
  657 
  658         to = timer2sbintime(kn->kn_sdata, kn->kn_sfflags);
  659         if (to < 0)
  660                 return (EINVAL);
  661 
  662         do {
  663                 ncallouts = kq_ncallouts;
  664                 if (ncallouts >= kq_calloutmax)
  665                         return (ENOMEM);
  666         } while (!atomic_cmpset_int(&kq_ncallouts, ncallouts, ncallouts + 1));
  667 
  668         kn->kn_flags |= EV_CLEAR;               /* automatically set */
  669         kn->kn_status &= ~KN_DETACHED;          /* knlist_add clears it */
  670         kn->kn_ptr.p_v = kc = malloc(sizeof(*kc), M_KQUEUE, M_WAITOK);
  671         callout_init(&kc->c, 1);
  672         kc->next = to + sbinuptime();
  673         kc->to = to;
  674         callout_reset_sbt_on(&kc->c, kc->next, 0, filt_timerexpire, kn,
  675             PCPU_GET(cpuid), C_ABSOLUTE);
  676 
  677         return (0);
  678 }
  679 
  680 static void
  681 filt_timerdetach(struct knote *kn)
  682 {
  683         struct kq_timer_cb_data *kc;
  684         unsigned int old;
  685 
  686         kc = kn->kn_ptr.p_v;
  687         callout_drain(&kc->c);
  688         free(kc, M_KQUEUE);
  689         old = atomic_fetchadd_int(&kq_ncallouts, -1);
  690         KASSERT(old > 0, ("Number of callouts cannot become negative"));
  691         kn->kn_status |= KN_DETACHED;   /* knlist_remove sets it */
  692 }
  693 
  694 static int
  695 filt_timer(struct knote *kn, long hint)
  696 {
  697 
  698         return (kn->kn_data != 0);
  699 }
  700 
  701 static int
  702 filt_userattach(struct knote *kn)
  703 {
  704 
  705         /* 
  706          * EVFILT_USER knotes are not attached to anything in the kernel.
  707          */ 
  708         kn->kn_hook = NULL;
  709         if (kn->kn_fflags & NOTE_TRIGGER)
  710                 kn->kn_hookid = 1;
  711         else
  712                 kn->kn_hookid = 0;
  713         return (0);
  714 }
  715 
  716 static void
  717 filt_userdetach(__unused struct knote *kn)
  718 {
  719 
  720         /*
  721          * EVFILT_USER knotes are not attached to anything in the kernel.
  722          */
  723 }
  724 
  725 static int
  726 filt_user(struct knote *kn, __unused long hint)
  727 {
  728 
  729         return (kn->kn_hookid);
  730 }
  731 
  732 static void
  733 filt_usertouch(struct knote *kn, struct kevent *kev, u_long type)
  734 {
  735         u_int ffctrl;
  736 
  737         switch (type) {
  738         case EVENT_REGISTER:
  739                 if (kev->fflags & NOTE_TRIGGER)
  740                         kn->kn_hookid = 1;
  741 
  742                 ffctrl = kev->fflags & NOTE_FFCTRLMASK;
  743                 kev->fflags &= NOTE_FFLAGSMASK;
  744                 switch (ffctrl) {
  745                 case NOTE_FFNOP:
  746                         break;
  747 
  748                 case NOTE_FFAND:
  749                         kn->kn_sfflags &= kev->fflags;
  750                         break;
  751 
  752                 case NOTE_FFOR:
  753                         kn->kn_sfflags |= kev->fflags;
  754                         break;
  755 
  756                 case NOTE_FFCOPY:
  757                         kn->kn_sfflags = kev->fflags;
  758                         break;
  759 
  760                 default:
  761                         /* XXX Return error? */
  762                         break;
  763                 }
  764                 kn->kn_sdata = kev->data;
  765                 if (kev->flags & EV_CLEAR) {
  766                         kn->kn_hookid = 0;
  767                         kn->kn_data = 0;
  768                         kn->kn_fflags = 0;
  769                 }
  770                 break;
  771 
  772         case EVENT_PROCESS:
  773                 *kev = kn->kn_kevent;
  774                 kev->fflags = kn->kn_sfflags;
  775                 kev->data = kn->kn_sdata;
  776                 if (kn->kn_flags & EV_CLEAR) {
  777                         kn->kn_hookid = 0;
  778                         kn->kn_data = 0;
  779                         kn->kn_fflags = 0;
  780                 }
  781                 break;
  782 
  783         default:
  784                 panic("filt_usertouch() - invalid type (%ld)", type);
  785                 break;
  786         }
  787 }
  788 
  789 int
  790 sys_kqueue(struct thread *td, struct kqueue_args *uap)
  791 {
  792 
  793         return (kern_kqueue(td, 0));
  794 }
  795 
  796 int
  797 kern_kqueue(struct thread *td, int flags)
  798 {
  799         struct filedesc *fdp;
  800         struct kqueue *kq;
  801         struct file *fp;
  802         int fd, error;
  803 
  804         fdp = td->td_proc->p_fd;
  805         error = falloc(td, &fp, &fd, flags);
  806         if (error)
  807                 goto done2;
  808 
  809         /* An extra reference on `fp' has been held for us by falloc(). */
  810         kq = malloc(sizeof *kq, M_KQUEUE, M_WAITOK | M_ZERO);
  811         mtx_init(&kq->kq_lock, "kqueue", NULL, MTX_DEF|MTX_DUPOK);
  812         TAILQ_INIT(&kq->kq_head);
  813         kq->kq_fdp = fdp;
  814         knlist_init_mtx(&kq->kq_sel.si_note, &kq->kq_lock);
  815         TASK_INIT(&kq->kq_task, 0, kqueue_task, kq);
  816 
  817         FILEDESC_XLOCK(fdp);
  818         TAILQ_INSERT_HEAD(&fdp->fd_kqlist, kq, kq_list);
  819         FILEDESC_XUNLOCK(fdp);
  820 
  821         finit(fp, FREAD | FWRITE, DTYPE_KQUEUE, kq, &kqueueops);
  822         fdrop(fp, td);
  823 
  824         td->td_retval[0] = fd;
  825 done2:
  826         return (error);
  827 }
  828 
  829 #ifdef KTRACE
  830 static size_t
  831 kev_iovlen(int n, u_int kgio)
  832 {
  833 
  834         if (n < 0 || n >= kgio / sizeof(struct kevent))
  835                 return (kgio);
  836         return (n * sizeof(struct kevent));
  837 }
  838 #endif
  839 
  840 #ifndef _SYS_SYSPROTO_H_
  841 struct kevent_args {
  842         int     fd;
  843         const struct kevent *changelist;
  844         int     nchanges;
  845         struct  kevent *eventlist;
  846         int     nevents;
  847         const struct timespec *timeout;
  848 };
  849 #endif
  850 int
  851 sys_kevent(struct thread *td, struct kevent_args *uap)
  852 {
  853         struct timespec ts, *tsp;
  854         struct kevent_copyops k_ops = { uap,
  855                                         kevent_copyout,
  856                                         kevent_copyin};
  857         int error;
  858 #ifdef KTRACE
  859         struct uio ktruio;
  860         struct iovec ktriov;
  861         struct uio *ktruioin = NULL;
  862         struct uio *ktruioout = NULL;
  863         u_int kgio;
  864 #endif
  865 
  866         if (uap->timeout != NULL) {
  867                 error = copyin(uap->timeout, &ts, sizeof(ts));
  868                 if (error)
  869                         return (error);
  870                 tsp = &ts;
  871         } else
  872                 tsp = NULL;
  873 
  874 #ifdef KTRACE
  875         if (KTRPOINT(td, KTR_GENIO)) {
  876                 kgio = ktr_geniosize;
  877                 ktriov.iov_base = uap->changelist;
  878                 ktriov.iov_len = kev_iovlen(uap->nchanges, kgio);
  879                 ktruio = (struct uio){ .uio_iov = &ktriov, .uio_iovcnt = 1,
  880                     .uio_segflg = UIO_USERSPACE, .uio_rw = UIO_READ,
  881                     .uio_td = td };
  882                 ktruioin = cloneuio(&ktruio);
  883                 ktriov.iov_base = uap->eventlist;
  884                 ktriov.iov_len = kev_iovlen(uap->nevents, kgio);
  885                 ktriov.iov_len = uap->nevents * sizeof(struct kevent);
  886                 ktruioout = cloneuio(&ktruio);
  887         }
  888 #endif
  889 
  890         error = kern_kevent(td, uap->fd, uap->nchanges, uap->nevents,
  891             &k_ops, tsp);
  892 
  893 #ifdef KTRACE
  894         if (ktruioin != NULL) {
  895                 ktruioin->uio_resid = kev_iovlen(uap->nchanges, kgio);
  896                 ktrgenio(uap->fd, UIO_WRITE, ktruioin, 0);
  897                 ktruioout->uio_resid = kev_iovlen(td->td_retval[0], kgio);
  898                 ktrgenio(uap->fd, UIO_READ, ktruioout, error);
  899         }
  900 #endif
  901 
  902         return (error);
  903 }
  904 
  905 /*
  906  * Copy 'count' items into the destination list pointed to by uap->eventlist.
  907  */
  908 static int
  909 kevent_copyout(void *arg, struct kevent *kevp, int count)
  910 {
  911         struct kevent_args *uap;
  912         int error;
  913 
  914         KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
  915         uap = (struct kevent_args *)arg;
  916 
  917         error = copyout(kevp, uap->eventlist, count * sizeof *kevp);
  918         if (error == 0)
  919                 uap->eventlist += count;
  920         return (error);
  921 }
  922 
  923 /*
  924  * Copy 'count' items from the list pointed to by uap->changelist.
  925  */
  926 static int
  927 kevent_copyin(void *arg, struct kevent *kevp, int count)
  928 {
  929         struct kevent_args *uap;
  930         int error;
  931 
  932         KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
  933         uap = (struct kevent_args *)arg;
  934 
  935         error = copyin(uap->changelist, kevp, count * sizeof *kevp);
  936         if (error == 0)
  937                 uap->changelist += count;
  938         return (error);
  939 }
  940 
  941 int
  942 kern_kevent(struct thread *td, int fd, int nchanges, int nevents,
  943     struct kevent_copyops *k_ops, const struct timespec *timeout)
  944 {
  945         cap_rights_t rights;
  946         struct file *fp;
  947         int error;
  948 
  949         cap_rights_init(&rights);
  950         if (nchanges > 0)
  951                 cap_rights_set(&rights, CAP_KQUEUE_CHANGE);
  952         if (nevents > 0)
  953                 cap_rights_set(&rights, CAP_KQUEUE_EVENT);
  954         error = fget(td, fd, &rights, &fp);
  955         if (error != 0)
  956                 return (error);
  957 
  958         error = kern_kevent_fp(td, fp, nchanges, nevents, k_ops, timeout);
  959         fdrop(fp, td);
  960 
  961         return (error);
  962 }
  963 
  964 int
  965 kern_kevent_fp(struct thread *td, struct file *fp, int nchanges, int nevents,
  966     struct kevent_copyops *k_ops, const struct timespec *timeout)
  967 {
  968         struct kevent keva[KQ_NEVENTS];
  969         struct kevent *kevp, *changes;
  970         struct kqueue *kq;
  971         int i, n, nerrors, error;
  972 
  973         error = kqueue_acquire(fp, &kq);
  974         if (error != 0)
  975                 return (error);
  976 
  977         nerrors = 0;
  978 
  979         while (nchanges > 0) {
  980                 n = nchanges > KQ_NEVENTS ? KQ_NEVENTS : nchanges;
  981                 error = k_ops->k_copyin(k_ops->arg, keva, n);
  982                 if (error)
  983                         goto done;
  984                 changes = keva;
  985                 for (i = 0; i < n; i++) {
  986                         kevp = &changes[i];
  987                         if (!kevp->filter)
  988                                 continue;
  989                         kevp->flags &= ~EV_SYSFLAGS;
  990                         error = kqueue_register(kq, kevp, td, 1);
  991                         if (error || (kevp->flags & EV_RECEIPT)) {
  992                                 if (nevents != 0) {
  993                                         kevp->flags = EV_ERROR;
  994                                         kevp->data = error;
  995                                         (void) k_ops->k_copyout(k_ops->arg,
  996                                             kevp, 1);
  997                                         nevents--;
  998                                         nerrors++;
  999                                 } else {
 1000                                         goto done;
 1001                                 }
 1002                         }
 1003                 }
 1004                 nchanges -= n;
 1005         }
 1006         if (nerrors) {
 1007                 td->td_retval[0] = nerrors;
 1008                 error = 0;
 1009                 goto done;
 1010         }
 1011 
 1012         error = kqueue_scan(kq, nevents, k_ops, timeout, keva, td);
 1013 done:
 1014         kqueue_release(kq, 0);
 1015         return (error);
 1016 }
 1017 
 1018 int
 1019 kqueue_add_filteropts(int filt, struct filterops *filtops)
 1020 {
 1021         int error;
 1022 
 1023         error = 0;
 1024         if (filt > 0 || filt + EVFILT_SYSCOUNT < 0) {
 1025                 printf(
 1026 "trying to add a filterop that is out of range: %d is beyond %d\n",
 1027                     ~filt, EVFILT_SYSCOUNT);
 1028                 return EINVAL;
 1029         }
 1030         mtx_lock(&filterops_lock);
 1031         if (sysfilt_ops[~filt].for_fop != &null_filtops &&
 1032             sysfilt_ops[~filt].for_fop != NULL)
 1033                 error = EEXIST;
 1034         else {
 1035                 sysfilt_ops[~filt].for_fop = filtops;
 1036                 sysfilt_ops[~filt].for_refcnt = 0;
 1037         }
 1038         mtx_unlock(&filterops_lock);
 1039 
 1040         return (error);
 1041 }
 1042 
 1043 int
 1044 kqueue_del_filteropts(int filt)
 1045 {
 1046         int error;
 1047 
 1048         error = 0;
 1049         if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
 1050                 return EINVAL;
 1051 
 1052         mtx_lock(&filterops_lock);
 1053         if (sysfilt_ops[~filt].for_fop == &null_filtops ||
 1054             sysfilt_ops[~filt].for_fop == NULL)
 1055                 error = EINVAL;
 1056         else if (sysfilt_ops[~filt].for_refcnt != 0)
 1057                 error = EBUSY;
 1058         else {
 1059                 sysfilt_ops[~filt].for_fop = &null_filtops;
 1060                 sysfilt_ops[~filt].for_refcnt = 0;
 1061         }
 1062         mtx_unlock(&filterops_lock);
 1063 
 1064         return error;
 1065 }
 1066 
 1067 static struct filterops *
 1068 kqueue_fo_find(int filt)
 1069 {
 1070 
 1071         if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
 1072                 return NULL;
 1073 
 1074         mtx_lock(&filterops_lock);
 1075         sysfilt_ops[~filt].for_refcnt++;
 1076         if (sysfilt_ops[~filt].for_fop == NULL)
 1077                 sysfilt_ops[~filt].for_fop = &null_filtops;
 1078         mtx_unlock(&filterops_lock);
 1079 
 1080         return sysfilt_ops[~filt].for_fop;
 1081 }
 1082 
 1083 static void
 1084 kqueue_fo_release(int filt)
 1085 {
 1086 
 1087         if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
 1088                 return;
 1089 
 1090         mtx_lock(&filterops_lock);
 1091         KASSERT(sysfilt_ops[~filt].for_refcnt > 0,
 1092             ("filter object refcount not valid on release"));
 1093         sysfilt_ops[~filt].for_refcnt--;
 1094         mtx_unlock(&filterops_lock);
 1095 }
 1096 
 1097 /*
 1098  * A ref to kq (obtained via kqueue_acquire) must be held.  waitok will
 1099  * influence if memory allocation should wait.  Make sure it is 0 if you
 1100  * hold any mutexes.
 1101  */
 1102 static int
 1103 kqueue_register(struct kqueue *kq, struct kevent *kev, struct thread *td, int waitok)
 1104 {
 1105         struct filterops *fops;
 1106         struct file *fp;
 1107         struct knote *kn, *tkn;
 1108         cap_rights_t rights;
 1109         int error, filt, event;
 1110         int haskqglobal, filedesc_unlock;
 1111 
 1112         fp = NULL;
 1113         kn = NULL;
 1114         error = 0;
 1115         haskqglobal = 0;
 1116         filedesc_unlock = 0;
 1117 
 1118         filt = kev->filter;
 1119         fops = kqueue_fo_find(filt);
 1120         if (fops == NULL)
 1121                 return EINVAL;
 1122 
 1123         tkn = knote_alloc(waitok);              /* prevent waiting with locks */
 1124 
 1125 findkn:
 1126         if (fops->f_isfd) {
 1127                 KASSERT(td != NULL, ("td is NULL"));
 1128                 if (kev->ident > INT_MAX)
 1129                         error = EBADF;
 1130                 else
 1131                         error = fget(td, kev->ident,
 1132                             cap_rights_init(&rights, CAP_EVENT), &fp);
 1133                 if (error)
 1134                         goto done;
 1135 
 1136                 if ((kev->flags & EV_ADD) == EV_ADD && kqueue_expand(kq, fops,
 1137                     kev->ident, 0) != 0) {
 1138                         /* try again */
 1139                         fdrop(fp, td);
 1140                         fp = NULL;
 1141                         error = kqueue_expand(kq, fops, kev->ident, waitok);
 1142                         if (error)
 1143                                 goto done;
 1144                         goto findkn;
 1145                 }
 1146 
 1147                 if (fp->f_type == DTYPE_KQUEUE) {
 1148                         /*
 1149                          * If we add some intelligence about what we are doing,
 1150                          * we should be able to support events on ourselves.
 1151                          * We need to know when we are doing this to prevent
 1152                          * getting both the knlist lock and the kq lock since
 1153                          * they are the same thing.
 1154                          */
 1155                         if (fp->f_data == kq) {
 1156                                 error = EINVAL;
 1157                                 goto done;
 1158                         }
 1159 
 1160                         /*
 1161                          * Pre-lock the filedesc before the global
 1162                          * lock mutex, see the comment in
 1163                          * kqueue_close().
 1164                          */
 1165                         FILEDESC_XLOCK(td->td_proc->p_fd);
 1166                         filedesc_unlock = 1;
 1167                         KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
 1168                 }
 1169 
 1170                 KQ_LOCK(kq);
 1171                 if (kev->ident < kq->kq_knlistsize) {
 1172                         SLIST_FOREACH(kn, &kq->kq_knlist[kev->ident], kn_link)
 1173                                 if (kev->filter == kn->kn_filter)
 1174                                         break;
 1175                 }
 1176         } else {
 1177                 if ((kev->flags & EV_ADD) == EV_ADD)
 1178                         kqueue_expand(kq, fops, kev->ident, waitok);
 1179 
 1180                 KQ_LOCK(kq);
 1181 
 1182                 /*
 1183                  * If possible, find an existing knote to use for this kevent.
 1184                  */
 1185                 if (kev->filter == EVFILT_PROC &&
 1186                     (kev->flags & (EV_FLAG1 | EV_FLAG2)) != 0) {
 1187                         /* This is an internal creation of a process tracking
 1188                          * note. Don't attempt to coalesce this with an
 1189                          * existing note.
 1190                          */
 1191                         ;                       
 1192                 } else if (kq->kq_knhashmask != 0) {
 1193                         struct klist *list;
 1194 
 1195                         list = &kq->kq_knhash[
 1196                             KN_HASH((u_long)kev->ident, kq->kq_knhashmask)];
 1197                         SLIST_FOREACH(kn, list, kn_link)
 1198                                 if (kev->ident == kn->kn_id &&
 1199                                     kev->filter == kn->kn_filter)
 1200                                         break;
 1201                 }
 1202         }
 1203 
 1204         /* knote is in the process of changing, wait for it to stabilize. */
 1205         if (kn != NULL && (kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 1206                 KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 1207                 if (filedesc_unlock) {
 1208                         FILEDESC_XUNLOCK(td->td_proc->p_fd);
 1209                         filedesc_unlock = 0;
 1210                 }
 1211                 kq->kq_state |= KQ_FLUXWAIT;
 1212                 msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqflxwt", 0);
 1213                 if (fp != NULL) {
 1214                         fdrop(fp, td);
 1215                         fp = NULL;
 1216                 }
 1217                 goto findkn;
 1218         }
 1219 
 1220         /*
 1221          * kn now contains the matching knote, or NULL if no match
 1222          */
 1223         if (kn == NULL) {
 1224                 if (kev->flags & EV_ADD) {
 1225                         kn = tkn;
 1226                         tkn = NULL;
 1227                         if (kn == NULL) {
 1228                                 KQ_UNLOCK(kq);
 1229                                 error = ENOMEM;
 1230                                 goto done;
 1231                         }
 1232                         kn->kn_fp = fp;
 1233                         kn->kn_kq = kq;
 1234                         kn->kn_fop = fops;
 1235                         /*
 1236                          * apply reference counts to knote structure, and
 1237                          * do not release it at the end of this routine.
 1238                          */
 1239                         fops = NULL;
 1240                         fp = NULL;
 1241 
 1242                         kn->kn_sfflags = kev->fflags;
 1243                         kn->kn_sdata = kev->data;
 1244                         kev->fflags = 0;
 1245                         kev->data = 0;
 1246                         kn->kn_kevent = *kev;
 1247                         kn->kn_kevent.flags &= ~(EV_ADD | EV_DELETE |
 1248                             EV_ENABLE | EV_DISABLE);
 1249                         kn->kn_status = KN_INFLUX|KN_DETACHED;
 1250 
 1251                         error = knote_attach(kn, kq);
 1252                         KQ_UNLOCK(kq);
 1253                         if (error != 0) {
 1254                                 tkn = kn;
 1255                                 goto done;
 1256                         }
 1257 
 1258                         if ((error = kn->kn_fop->f_attach(kn)) != 0) {
 1259                                 knote_drop(kn, td);
 1260                                 goto done;
 1261                         }
 1262                         KN_LIST_LOCK(kn);
 1263                         goto done_ev_add;
 1264                 } else {
 1265                         /* No matching knote and the EV_ADD flag is not set. */
 1266                         KQ_UNLOCK(kq);
 1267                         error = ENOENT;
 1268                         goto done;
 1269                 }
 1270         }
 1271         
 1272         if (kev->flags & EV_DELETE) {
 1273                 kn->kn_status |= KN_INFLUX;
 1274                 KQ_UNLOCK(kq);
 1275                 if (!(kn->kn_status & KN_DETACHED))
 1276                         kn->kn_fop->f_detach(kn);
 1277                 knote_drop(kn, td);
 1278                 goto done;
 1279         }
 1280 
 1281         /*
 1282          * The user may change some filter values after the initial EV_ADD,
 1283          * but doing so will not reset any filter which has already been
 1284          * triggered.
 1285          */
 1286         kn->kn_status |= KN_INFLUX | KN_SCAN;
 1287         KQ_UNLOCK(kq);
 1288         KN_LIST_LOCK(kn);
 1289         kn->kn_kevent.udata = kev->udata;
 1290         if (!fops->f_isfd && fops->f_touch != NULL) {
 1291                 fops->f_touch(kn, kev, EVENT_REGISTER);
 1292         } else {
 1293                 kn->kn_sfflags = kev->fflags;
 1294                 kn->kn_sdata = kev->data;
 1295         }
 1296 
 1297         /*
 1298          * We can get here with kn->kn_knlist == NULL.  This can happen when
 1299          * the initial attach event decides that the event is "completed" 
 1300          * already.  i.e. filt_procattach is called on a zombie process.  It
 1301          * will call filt_proc which will remove it from the list, and NULL
 1302          * kn_knlist.
 1303          */
 1304 done_ev_add:
 1305         event = kn->kn_fop->f_event(kn, 0);
 1306         KQ_LOCK(kq);
 1307         if (event)
 1308                 KNOTE_ACTIVATE(kn, 1);
 1309         kn->kn_status &= ~(KN_INFLUX | KN_SCAN);
 1310         KN_LIST_UNLOCK(kn);
 1311 
 1312         if ((kev->flags & EV_DISABLE) &&
 1313             ((kn->kn_status & KN_DISABLED) == 0)) {
 1314                 kn->kn_status |= KN_DISABLED;
 1315         }
 1316 
 1317         if ((kev->flags & EV_ENABLE) && (kn->kn_status & KN_DISABLED)) {
 1318                 kn->kn_status &= ~KN_DISABLED;
 1319                 if ((kn->kn_status & KN_ACTIVE) &&
 1320                     ((kn->kn_status & KN_QUEUED) == 0))
 1321                         knote_enqueue(kn);
 1322         }
 1323         KQ_UNLOCK_FLUX(kq);
 1324 
 1325 done:
 1326         KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 1327         if (filedesc_unlock)
 1328                 FILEDESC_XUNLOCK(td->td_proc->p_fd);
 1329         if (fp != NULL)
 1330                 fdrop(fp, td);
 1331         if (tkn != NULL)
 1332                 knote_free(tkn);
 1333         if (fops != NULL)
 1334                 kqueue_fo_release(filt);
 1335         return (error);
 1336 }
 1337 
 1338 static int
 1339 kqueue_acquire(struct file *fp, struct kqueue **kqp)
 1340 {
 1341         int error;
 1342         struct kqueue *kq;
 1343 
 1344         error = 0;
 1345 
 1346         kq = fp->f_data;
 1347         if (fp->f_type != DTYPE_KQUEUE || kq == NULL)
 1348                 return (EBADF);
 1349         *kqp = kq;
 1350         KQ_LOCK(kq);
 1351         if ((kq->kq_state & KQ_CLOSING) == KQ_CLOSING) {
 1352                 KQ_UNLOCK(kq);
 1353                 return (EBADF);
 1354         }
 1355         kq->kq_refcnt++;
 1356         KQ_UNLOCK(kq);
 1357 
 1358         return error;
 1359 }
 1360 
 1361 static void
 1362 kqueue_release(struct kqueue *kq, int locked)
 1363 {
 1364         if (locked)
 1365                 KQ_OWNED(kq);
 1366         else
 1367                 KQ_LOCK(kq);
 1368         kq->kq_refcnt--;
 1369         if (kq->kq_refcnt == 1)
 1370                 wakeup(&kq->kq_refcnt);
 1371         if (!locked)
 1372                 KQ_UNLOCK(kq);
 1373 }
 1374 
 1375 static void
 1376 kqueue_schedtask(struct kqueue *kq)
 1377 {
 1378 
 1379         KQ_OWNED(kq);
 1380         KASSERT(((kq->kq_state & KQ_TASKDRAIN) != KQ_TASKDRAIN),
 1381             ("scheduling kqueue task while draining"));
 1382 
 1383         if ((kq->kq_state & KQ_TASKSCHED) != KQ_TASKSCHED) {
 1384                 taskqueue_enqueue(taskqueue_kqueue, &kq->kq_task);
 1385                 kq->kq_state |= KQ_TASKSCHED;
 1386         }
 1387 }
 1388 
 1389 /*
 1390  * Expand the kq to make sure we have storage for fops/ident pair.
 1391  *
 1392  * Return 0 on success (or no work necessary), return errno on failure.
 1393  *
 1394  * Not calling hashinit w/ waitok (proper malloc flag) should be safe.
 1395  * If kqueue_register is called from a non-fd context, there usually/should
 1396  * be no locks held.
 1397  */
 1398 static int
 1399 kqueue_expand(struct kqueue *kq, struct filterops *fops, uintptr_t ident,
 1400         int waitok)
 1401 {
 1402         struct klist *list, *tmp_knhash, *to_free;
 1403         u_long tmp_knhashmask;
 1404         int size;
 1405         int fd;
 1406         int mflag = waitok ? M_WAITOK : M_NOWAIT;
 1407 
 1408         KQ_NOTOWNED(kq);
 1409 
 1410         to_free = NULL;
 1411         if (fops->f_isfd) {
 1412                 fd = ident;
 1413                 if (kq->kq_knlistsize <= fd) {
 1414                         size = kq->kq_knlistsize;
 1415                         while (size <= fd)
 1416                                 size += KQEXTENT;
 1417                         list = malloc(size * sizeof(*list), M_KQUEUE, mflag);
 1418                         if (list == NULL)
 1419                                 return ENOMEM;
 1420                         KQ_LOCK(kq);
 1421                         if (kq->kq_knlistsize > fd) {
 1422                                 to_free = list;
 1423                                 list = NULL;
 1424                         } else {
 1425                                 if (kq->kq_knlist != NULL) {
 1426                                         bcopy(kq->kq_knlist, list,
 1427                                             kq->kq_knlistsize * sizeof(*list));
 1428                                         to_free = kq->kq_knlist;
 1429                                         kq->kq_knlist = NULL;
 1430                                 }
 1431                                 bzero((caddr_t)list +
 1432                                     kq->kq_knlistsize * sizeof(*list),
 1433                                     (size - kq->kq_knlistsize) * sizeof(*list));
 1434                                 kq->kq_knlistsize = size;
 1435                                 kq->kq_knlist = list;
 1436                         }
 1437                         KQ_UNLOCK(kq);
 1438                 }
 1439         } else {
 1440                 if (kq->kq_knhashmask == 0) {
 1441                         tmp_knhash = hashinit(KN_HASHSIZE, M_KQUEUE,
 1442                             &tmp_knhashmask);
 1443                         if (tmp_knhash == NULL)
 1444                                 return ENOMEM;
 1445                         KQ_LOCK(kq);
 1446                         if (kq->kq_knhashmask == 0) {
 1447                                 kq->kq_knhash = tmp_knhash;
 1448                                 kq->kq_knhashmask = tmp_knhashmask;
 1449                         } else {
 1450                                 to_free = tmp_knhash;
 1451                         }
 1452                         KQ_UNLOCK(kq);
 1453                 }
 1454         }
 1455         free(to_free, M_KQUEUE);
 1456 
 1457         KQ_NOTOWNED(kq);
 1458         return 0;
 1459 }
 1460 
 1461 static void
 1462 kqueue_task(void *arg, int pending)
 1463 {
 1464         struct kqueue *kq;
 1465         int haskqglobal;
 1466 
 1467         haskqglobal = 0;
 1468         kq = arg;
 1469 
 1470         KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
 1471         KQ_LOCK(kq);
 1472 
 1473         KNOTE_LOCKED(&kq->kq_sel.si_note, 0);
 1474 
 1475         kq->kq_state &= ~KQ_TASKSCHED;
 1476         if ((kq->kq_state & KQ_TASKDRAIN) == KQ_TASKDRAIN) {
 1477                 wakeup(&kq->kq_state);
 1478         }
 1479         KQ_UNLOCK(kq);
 1480         KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 1481 }
 1482 
 1483 /*
 1484  * Scan, update kn_data (if not ONESHOT), and copyout triggered events.
 1485  * We treat KN_MARKER knotes as if they are INFLUX.
 1486  */
 1487 static int
 1488 kqueue_scan(struct kqueue *kq, int maxevents, struct kevent_copyops *k_ops,
 1489     const struct timespec *tsp, struct kevent *keva, struct thread *td)
 1490 {
 1491         struct kevent *kevp;
 1492         struct knote *kn, *marker;
 1493         sbintime_t asbt, rsbt;
 1494         int count, error, haskqglobal, influx, nkev, touch;
 1495 
 1496         count = maxevents;
 1497         nkev = 0;
 1498         error = 0;
 1499         haskqglobal = 0;
 1500 
 1501         if (maxevents == 0)
 1502                 goto done_nl;
 1503 
 1504         rsbt = 0;
 1505         if (tsp != NULL) {
 1506                 if (tsp->tv_sec < 0 || tsp->tv_nsec < 0 ||
 1507                     tsp->tv_nsec >= 1000000000) {
 1508                         error = EINVAL;
 1509                         goto done_nl;
 1510                 }
 1511                 if (timespecisset(tsp)) {
 1512                         if (tsp->tv_sec <= INT32_MAX) {
 1513                                 rsbt = tstosbt(*tsp);
 1514                                 if (TIMESEL(&asbt, rsbt))
 1515                                         asbt += tc_tick_sbt;
 1516                                 if (asbt <= SBT_MAX - rsbt)
 1517                                         asbt += rsbt;
 1518                                 else
 1519                                         asbt = 0;
 1520                                 rsbt >>= tc_precexp;
 1521                         } else
 1522                                 asbt = 0;
 1523                 } else
 1524                         asbt = -1;
 1525         } else
 1526                 asbt = 0;
 1527         marker = knote_alloc(1);
 1528         if (marker == NULL) {
 1529                 error = ENOMEM;
 1530                 goto done_nl;
 1531         }
 1532         marker->kn_status = KN_MARKER;
 1533         KQ_LOCK(kq);
 1534 
 1535 retry:
 1536         kevp = keva;
 1537         if (kq->kq_count == 0) {
 1538                 if (asbt == -1) {
 1539                         error = EWOULDBLOCK;
 1540                 } else {
 1541                         kq->kq_state |= KQ_SLEEP;
 1542                         error = msleep_sbt(kq, &kq->kq_lock, PSOCK | PCATCH,
 1543                             "kqread", asbt, rsbt, C_ABSOLUTE);
 1544                 }
 1545                 if (error == 0)
 1546                         goto retry;
 1547                 /* don't restart after signals... */
 1548                 if (error == ERESTART)
 1549                         error = EINTR;
 1550                 else if (error == EWOULDBLOCK)
 1551                         error = 0;
 1552                 goto done;
 1553         }
 1554 
 1555         TAILQ_INSERT_TAIL(&kq->kq_head, marker, kn_tqe);
 1556         influx = 0;
 1557         while (count) {
 1558                 KQ_OWNED(kq);
 1559                 kn = TAILQ_FIRST(&kq->kq_head);
 1560 
 1561                 if ((kn->kn_status == KN_MARKER && kn != marker) ||
 1562                     (kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 1563                         if (influx) {
 1564                                 influx = 0;
 1565                                 KQ_FLUX_WAKEUP(kq);
 1566                         }
 1567                         kq->kq_state |= KQ_FLUXWAIT;
 1568                         error = msleep(kq, &kq->kq_lock, PSOCK,
 1569                             "kqflxwt", 0);
 1570                         continue;
 1571                 }
 1572 
 1573                 TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
 1574                 if ((kn->kn_status & KN_DISABLED) == KN_DISABLED) {
 1575                         kn->kn_status &= ~KN_QUEUED;
 1576                         kq->kq_count--;
 1577                         continue;
 1578                 }
 1579                 if (kn == marker) {
 1580                         KQ_FLUX_WAKEUP(kq);
 1581                         if (count == maxevents)
 1582                                 goto retry;
 1583                         goto done;
 1584                 }
 1585                 KASSERT((kn->kn_status & KN_INFLUX) == 0,
 1586                     ("KN_INFLUX set when not suppose to be"));
 1587 
 1588                 if ((kn->kn_flags & EV_DROP) == EV_DROP) {
 1589                         kn->kn_status &= ~KN_QUEUED;
 1590                         kn->kn_status |= KN_INFLUX;
 1591                         kq->kq_count--;
 1592                         KQ_UNLOCK(kq);
 1593                         /*
 1594                          * We don't need to lock the list since we've marked
 1595                          * it _INFLUX.
 1596                          */
 1597                         if (!(kn->kn_status & KN_DETACHED))
 1598                                 kn->kn_fop->f_detach(kn);
 1599                         knote_drop(kn, td);
 1600                         KQ_LOCK(kq);
 1601                         continue;
 1602                 } else if ((kn->kn_flags & EV_ONESHOT) == EV_ONESHOT) {
 1603                         kn->kn_status &= ~KN_QUEUED;
 1604                         kn->kn_status |= KN_INFLUX;
 1605                         kq->kq_count--;
 1606                         KQ_UNLOCK(kq);
 1607                         /*
 1608                          * We don't need to lock the list since we've marked
 1609                          * it _INFLUX.
 1610                          */
 1611                         *kevp = kn->kn_kevent;
 1612                         if (!(kn->kn_status & KN_DETACHED))
 1613                                 kn->kn_fop->f_detach(kn);
 1614                         knote_drop(kn, td);
 1615                         KQ_LOCK(kq);
 1616                         kn = NULL;
 1617                 } else {
 1618                         kn->kn_status |= KN_INFLUX | KN_SCAN;
 1619                         KQ_UNLOCK(kq);
 1620                         if ((kn->kn_status & KN_KQUEUE) == KN_KQUEUE)
 1621                                 KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
 1622                         KN_LIST_LOCK(kn);
 1623                         if (kn->kn_fop->f_event(kn, 0) == 0) {
 1624                                 KQ_LOCK(kq);
 1625                                 KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 1626                                 kn->kn_status &=
 1627                                     ~(KN_QUEUED | KN_ACTIVE | KN_INFLUX |
 1628                                     KN_SCAN);
 1629                                 kq->kq_count--;
 1630                                 KN_LIST_UNLOCK(kn);
 1631                                 influx = 1;
 1632                                 continue;
 1633                         }
 1634                         touch = (!kn->kn_fop->f_isfd &&
 1635                             kn->kn_fop->f_touch != NULL);
 1636                         if (touch)
 1637                                 kn->kn_fop->f_touch(kn, kevp, EVENT_PROCESS);
 1638                         else
 1639                                 *kevp = kn->kn_kevent;
 1640                         KQ_LOCK(kq);
 1641                         KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
 1642                         if (kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) {
 1643                                 /* 
 1644                                  * Manually clear knotes who weren't 
 1645                                  * 'touch'ed.
 1646                                  */
 1647                                 if (touch == 0 && kn->kn_flags & EV_CLEAR) {
 1648                                         kn->kn_data = 0;
 1649                                         kn->kn_fflags = 0;
 1650                                 }
 1651                                 if (kn->kn_flags & EV_DISPATCH)
 1652                                         kn->kn_status |= KN_DISABLED;
 1653                                 kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
 1654                                 kq->kq_count--;
 1655                         } else
 1656                                 TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
 1657                         
 1658                         kn->kn_status &= ~(KN_INFLUX | KN_SCAN);
 1659                         KN_LIST_UNLOCK(kn);
 1660                         influx = 1;
 1661                 }
 1662 
 1663                 /* we are returning a copy to the user */
 1664                 kevp++;
 1665                 nkev++;
 1666                 count--;
 1667 
 1668                 if (nkev == KQ_NEVENTS) {
 1669                         influx = 0;
 1670                         KQ_UNLOCK_FLUX(kq);
 1671                         error = k_ops->k_copyout(k_ops->arg, keva, nkev);
 1672                         nkev = 0;
 1673                         kevp = keva;
 1674                         KQ_LOCK(kq);
 1675                         if (error)
 1676                                 break;
 1677                 }
 1678         }
 1679         TAILQ_REMOVE(&kq->kq_head, marker, kn_tqe);
 1680 done:
 1681         KQ_OWNED(kq);
 1682         KQ_UNLOCK_FLUX(kq);
 1683         knote_free(marker);
 1684 done_nl:
 1685         KQ_NOTOWNED(kq);
 1686         if (nkev != 0)
 1687                 error = k_ops->k_copyout(k_ops->arg, keva, nkev);
 1688         td->td_retval[0] = maxevents - count;
 1689         return (error);
 1690 }
 1691 
 1692 /*
 1693  * XXX
 1694  * This could be expanded to call kqueue_scan, if desired.
 1695  */
 1696 /*ARGSUSED*/
 1697 static int
 1698 kqueue_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 1699         int flags, struct thread *td)
 1700 {
 1701         return (ENXIO);
 1702 }
 1703 
 1704 /*ARGSUSED*/
 1705 static int
 1706 kqueue_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 1707          int flags, struct thread *td)
 1708 {
 1709         return (ENXIO);
 1710 }
 1711 
 1712 /*ARGSUSED*/
 1713 static int
 1714 kqueue_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 1715         struct thread *td)
 1716 {
 1717 
 1718         return (EINVAL);
 1719 }
 1720 
 1721 /*ARGSUSED*/
 1722 static int
 1723 kqueue_ioctl(struct file *fp, u_long cmd, void *data,
 1724         struct ucred *active_cred, struct thread *td)
 1725 {
 1726         /*
 1727          * Enabling sigio causes two major problems:
 1728          * 1) infinite recursion:
 1729          * Synopsys: kevent is being used to track signals and have FIOASYNC
 1730          * set.  On receipt of a signal this will cause a kqueue to recurse
 1731          * into itself over and over.  Sending the sigio causes the kqueue
 1732          * to become ready, which in turn posts sigio again, forever.
 1733          * Solution: this can be solved by setting a flag in the kqueue that
 1734          * we have a SIGIO in progress.
 1735          * 2) locking problems:
 1736          * Synopsys: Kqueue is a leaf subsystem, but adding signalling puts
 1737          * us above the proc and pgrp locks.
 1738          * Solution: Post a signal using an async mechanism, being sure to
 1739          * record a generation count in the delivery so that we do not deliver
 1740          * a signal to the wrong process.
 1741          *
 1742          * Note, these two mechanisms are somewhat mutually exclusive!
 1743          */
 1744 #if 0
 1745         struct kqueue *kq;
 1746 
 1747         kq = fp->f_data;
 1748         switch (cmd) {
 1749         case FIOASYNC:
 1750                 if (*(int *)data) {
 1751                         kq->kq_state |= KQ_ASYNC;
 1752                 } else {
 1753                         kq->kq_state &= ~KQ_ASYNC;
 1754                 }
 1755                 return (0);
 1756 
 1757         case FIOSETOWN:
 1758                 return (fsetown(*(int *)data, &kq->kq_sigio));
 1759 
 1760         case FIOGETOWN:
 1761                 *(int *)data = fgetown(&kq->kq_sigio);
 1762                 return (0);
 1763         }
 1764 #endif
 1765 
 1766         return (ENOTTY);
 1767 }
 1768 
 1769 /*ARGSUSED*/
 1770 static int
 1771 kqueue_poll(struct file *fp, int events, struct ucred *active_cred,
 1772         struct thread *td)
 1773 {
 1774         struct kqueue *kq;
 1775         int revents = 0;
 1776         int error;
 1777 
 1778         if ((error = kqueue_acquire(fp, &kq)))
 1779                 return POLLERR;
 1780 
 1781         KQ_LOCK(kq);
 1782         if (events & (POLLIN | POLLRDNORM)) {
 1783                 if (kq->kq_count) {
 1784                         revents |= events & (POLLIN | POLLRDNORM);
 1785                 } else {
 1786                         selrecord(td, &kq->kq_sel);
 1787                         if (SEL_WAITING(&kq->kq_sel))
 1788                                 kq->kq_state |= KQ_SEL;
 1789                 }
 1790         }
 1791         kqueue_release(kq, 1);
 1792         KQ_UNLOCK(kq);
 1793         return (revents);
 1794 }
 1795 
 1796 /*ARGSUSED*/
 1797 static int
 1798 kqueue_stat(struct file *fp, struct stat *st, struct ucred *active_cred,
 1799         struct thread *td)
 1800 {
 1801 
 1802         bzero((void *)st, sizeof *st);
 1803         /*
 1804          * We no longer return kq_count because the unlocked value is useless.
 1805          * If you spent all this time getting the count, why not spend your
 1806          * syscall better by calling kevent?
 1807          *
 1808          * XXX - This is needed for libc_r.
 1809          */
 1810         st->st_mode = S_IFIFO;
 1811         return (0);
 1812 }
 1813 
 1814 /*ARGSUSED*/
 1815 static int
 1816 kqueue_close(struct file *fp, struct thread *td)
 1817 {
 1818         struct kqueue *kq = fp->f_data;
 1819         struct filedesc *fdp;
 1820         struct knote *kn;
 1821         int i;
 1822         int error;
 1823         int filedesc_unlock;
 1824 
 1825         if ((error = kqueue_acquire(fp, &kq)))
 1826                 return error;
 1827 
 1828         filedesc_unlock = 0;
 1829         KQ_LOCK(kq);
 1830 
 1831         KASSERT((kq->kq_state & KQ_CLOSING) != KQ_CLOSING,
 1832             ("kqueue already closing"));
 1833         kq->kq_state |= KQ_CLOSING;
 1834         if (kq->kq_refcnt > 1)
 1835                 msleep(&kq->kq_refcnt, &kq->kq_lock, PSOCK, "kqclose", 0);
 1836 
 1837         KASSERT(kq->kq_refcnt == 1, ("other refs are out there!"));
 1838         fdp = kq->kq_fdp;
 1839 
 1840         KASSERT(knlist_empty(&kq->kq_sel.si_note),
 1841             ("kqueue's knlist not empty"));
 1842 
 1843         for (i = 0; i < kq->kq_knlistsize; i++) {
 1844                 while ((kn = SLIST_FIRST(&kq->kq_knlist[i])) != NULL) {
 1845                         if ((kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 1846                                 kq->kq_state |= KQ_FLUXWAIT;
 1847                                 msleep(kq, &kq->kq_lock, PSOCK, "kqclo1", 0);
 1848                                 continue;
 1849                         }
 1850                         kn->kn_status |= KN_INFLUX;
 1851                         KQ_UNLOCK(kq);
 1852                         if (!(kn->kn_status & KN_DETACHED))
 1853                                 kn->kn_fop->f_detach(kn);
 1854                         knote_drop(kn, td);
 1855                         KQ_LOCK(kq);
 1856                 }
 1857         }
 1858         if (kq->kq_knhashmask != 0) {
 1859                 for (i = 0; i <= kq->kq_knhashmask; i++) {
 1860                         while ((kn = SLIST_FIRST(&kq->kq_knhash[i])) != NULL) {
 1861                                 if ((kn->kn_status & KN_INFLUX) == KN_INFLUX) {
 1862                                         kq->kq_state |= KQ_FLUXWAIT;
 1863                                         msleep(kq, &kq->kq_lock, PSOCK,
 1864                                                "kqclo2", 0);
 1865                                         continue;
 1866                                 }
 1867                                 kn->kn_status |= KN_INFLUX;
 1868                                 KQ_UNLOCK(kq);
 1869                                 if (!(kn->kn_status & KN_DETACHED))
 1870                                         kn->kn_fop->f_detach(kn);
 1871                                 knote_drop(kn, td);
 1872                                 KQ_LOCK(kq);
 1873                         }
 1874                 }
 1875         }
 1876 
 1877         if ((kq->kq_state & KQ_TASKSCHED) == KQ_TASKSCHED) {
 1878                 kq->kq_state |= KQ_TASKDRAIN;
 1879                 msleep(&kq->kq_state, &kq->kq_lock, PSOCK, "kqtqdr", 0);
 1880         }
 1881 
 1882         if ((kq->kq_state & KQ_SEL) == KQ_SEL) {
 1883                 selwakeuppri(&kq->kq_sel, PSOCK);
 1884                 if (!SEL_WAITING(&kq->kq_sel))
 1885                         kq->kq_state &= ~KQ_SEL;
 1886         }
 1887 
 1888         KQ_UNLOCK(kq);
 1889 
 1890         /*
 1891          * We could be called due to the knote_drop() doing fdrop(),
 1892          * called from kqueue_register().  In this case the global
 1893          * lock is owned, and filedesc sx is locked before, to not
 1894          * take the sleepable lock after non-sleepable.
 1895          */
 1896         if (!sx_xlocked(FILEDESC_LOCK(fdp))) {
 1897                 FILEDESC_XLOCK(fdp);
 1898                 filedesc_unlock = 1;
 1899         } else
 1900                 filedesc_unlock = 0;
 1901         TAILQ_REMOVE(&fdp->fd_kqlist, kq, kq_list);
 1902         if (filedesc_unlock)
 1903                 FILEDESC_XUNLOCK(fdp);
 1904 
 1905         seldrain(&kq->kq_sel);
 1906         knlist_destroy(&kq->kq_sel.si_note);
 1907         mtx_destroy(&kq->kq_lock);
 1908         kq->kq_fdp = NULL;
 1909 
 1910         if (kq->kq_knhash != NULL)
 1911                 free(kq->kq_knhash, M_KQUEUE);
 1912         if (kq->kq_knlist != NULL)
 1913                 free(kq->kq_knlist, M_KQUEUE);
 1914 
 1915         funsetown(&kq->kq_sigio);
 1916         free(kq, M_KQUEUE);
 1917         fp->f_data = NULL;
 1918 
 1919         return (0);
 1920 }
 1921 
 1922 static void
 1923 kqueue_wakeup(struct kqueue *kq)
 1924 {
 1925         KQ_OWNED(kq);
 1926 
 1927         if ((kq->kq_state & KQ_SLEEP) == KQ_SLEEP) {
 1928                 kq->kq_state &= ~KQ_SLEEP;
 1929                 wakeup(kq);
 1930         }
 1931         if ((kq->kq_state & KQ_SEL) == KQ_SEL) {
 1932                 selwakeuppri(&kq->kq_sel, PSOCK);
 1933                 if (!SEL_WAITING(&kq->kq_sel))
 1934                         kq->kq_state &= ~KQ_SEL;
 1935         }
 1936         if (!knlist_empty(&kq->kq_sel.si_note))
 1937                 kqueue_schedtask(kq);
 1938         if ((kq->kq_state & KQ_ASYNC) == KQ_ASYNC) {
 1939                 pgsigio(&kq->kq_sigio, SIGIO, 0);
 1940         }
 1941 }
 1942 
 1943 /*
 1944  * Walk down a list of knotes, activating them if their event has triggered.
 1945  *
 1946  * There is a possibility to optimize in the case of one kq watching another.
 1947  * Instead of scheduling a task to wake it up, you could pass enough state
 1948  * down the chain to make up the parent kqueue.  Make this code functional
 1949  * first.
 1950  */
 1951 void
 1952 knote(struct knlist *list, long hint, int lockflags)
 1953 {
 1954         struct kqueue *kq;
 1955         struct knote *kn, *tkn;
 1956         int error;
 1957         bool own_influx;
 1958 
 1959         if (list == NULL)
 1960                 return;
 1961 
 1962         KNL_ASSERT_LOCK(list, lockflags & KNF_LISTLOCKED);
 1963 
 1964         if ((lockflags & KNF_LISTLOCKED) == 0)
 1965                 list->kl_lock(list->kl_lockarg); 
 1966 
 1967         /*
 1968          * If we unlock the list lock (and set KN_INFLUX), we can
 1969          * eliminate the kqueue scheduling, but this will introduce
 1970          * four lock/unlock's for each knote to test.  Also, marker
 1971          * would be needed to keep iteration position, since filters
 1972          * or other threads could remove events.
 1973          */
 1974         SLIST_FOREACH_SAFE(kn, &list->kl_list, kn_selnext, tkn) {
 1975                 kq = kn->kn_kq;
 1976                 KQ_LOCK(kq);
 1977                 if ((kn->kn_status & (KN_INFLUX | KN_SCAN)) == KN_INFLUX) {
 1978                         /*
 1979                          * Do not process the influx notes, except for
 1980                          * the influx coming from the kq unlock in the
 1981                          * kqueue_scan().  In the later case, we do
 1982                          * not interfere with the scan, since the code
 1983                          * fragment in kqueue_scan() locks the knlist,
 1984                          * and cannot proceed until we finished.
 1985                          */
 1986                         KQ_UNLOCK(kq);
 1987                 } else if ((lockflags & KNF_NOKQLOCK) != 0) {
 1988                         own_influx = (kn->kn_status & KN_INFLUX) == 0;
 1989                         if (own_influx)
 1990                                 kn->kn_status |= KN_INFLUX;
 1991                         KQ_UNLOCK(kq);
 1992                         error = kn->kn_fop->f_event(kn, hint);
 1993                         KQ_LOCK(kq);
 1994                         if (own_influx)
 1995                                 kn->kn_status &= ~KN_INFLUX;
 1996                         if (error)
 1997                                 KNOTE_ACTIVATE(kn, 1);
 1998                         KQ_UNLOCK_FLUX(kq);
 1999                 } else {
 2000                         kn->kn_status |= KN_HASKQLOCK;
 2001                         if (kn->kn_fop->f_event(kn, hint))
 2002                                 KNOTE_ACTIVATE(kn, 1);
 2003                         kn->kn_status &= ~KN_HASKQLOCK;
 2004                         KQ_UNLOCK(kq);
 2005                 }
 2006         }
 2007         if ((lockflags & KNF_LISTLOCKED) == 0)
 2008                 list->kl_unlock(list->kl_lockarg); 
 2009 }
 2010 
 2011 /*
 2012  * add a knote to a knlist
 2013  */
 2014 void
 2015 knlist_add(struct knlist *knl, struct knote *kn, int islocked)
 2016 {
 2017         KNL_ASSERT_LOCK(knl, islocked);
 2018         KQ_NOTOWNED(kn->kn_kq);
 2019         KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) ==
 2020             (KN_INFLUX|KN_DETACHED), ("knote not KN_INFLUX and KN_DETACHED"));
 2021         if (!islocked)
 2022                 knl->kl_lock(knl->kl_lockarg);
 2023         SLIST_INSERT_HEAD(&knl->kl_list, kn, kn_selnext);
 2024         if (!islocked)
 2025                 knl->kl_unlock(knl->kl_lockarg);
 2026         KQ_LOCK(kn->kn_kq);
 2027         kn->kn_knlist = knl;
 2028         kn->kn_status &= ~KN_DETACHED;
 2029         KQ_UNLOCK(kn->kn_kq);
 2030 }
 2031 
 2032 static void
 2033 knlist_remove_kq(struct knlist *knl, struct knote *kn, int knlislocked, int kqislocked)
 2034 {
 2035         KASSERT(!(!!kqislocked && !knlislocked), ("kq locked w/o knl locked"));
 2036         KNL_ASSERT_LOCK(knl, knlislocked);
 2037         mtx_assert(&kn->kn_kq->kq_lock, kqislocked ? MA_OWNED : MA_NOTOWNED);
 2038         if (!kqislocked)
 2039                 KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) == KN_INFLUX,
 2040     ("knlist_remove called w/o knote being KN_INFLUX or already removed"));
 2041         if (!knlislocked)
 2042                 knl->kl_lock(knl->kl_lockarg);
 2043         SLIST_REMOVE(&knl->kl_list, kn, knote, kn_selnext);
 2044         kn->kn_knlist = NULL;
 2045         if (!knlislocked)
 2046                 knl->kl_unlock(knl->kl_lockarg);
 2047         if (!kqislocked)
 2048                 KQ_LOCK(kn->kn_kq);
 2049         kn->kn_status |= KN_DETACHED;
 2050         if (!kqislocked)
 2051                 KQ_UNLOCK(kn->kn_kq);
 2052 }
 2053 
 2054 /*
 2055  * remove knote from the specified knlist
 2056  */
 2057 void
 2058 knlist_remove(struct knlist *knl, struct knote *kn, int islocked)
 2059 {
 2060 
 2061         knlist_remove_kq(knl, kn, islocked, 0);
 2062 }
 2063 
 2064 /*
 2065  * remove knote from the specified knlist while in f_event handler.
 2066  */
 2067 void
 2068 knlist_remove_inevent(struct knlist *knl, struct knote *kn)
 2069 {
 2070 
 2071         knlist_remove_kq(knl, kn, 1,
 2072             (kn->kn_status & KN_HASKQLOCK) == KN_HASKQLOCK);
 2073 }
 2074 
 2075 int
 2076 knlist_empty(struct knlist *knl)
 2077 {
 2078 
 2079         KNL_ASSERT_LOCKED(knl);
 2080         return (SLIST_EMPTY(&knl->kl_list));
 2081 }
 2082 
 2083 static struct mtx knlist_lock;
 2084 MTX_SYSINIT(knlist_lock, &knlist_lock, "knlist lock for lockless objects",
 2085     MTX_DEF);
 2086 static void knlist_mtx_lock(void *arg);
 2087 static void knlist_mtx_unlock(void *arg);
 2088 
 2089 static void
 2090 knlist_mtx_lock(void *arg)
 2091 {
 2092 
 2093         mtx_lock((struct mtx *)arg);
 2094 }
 2095 
 2096 static void
 2097 knlist_mtx_unlock(void *arg)
 2098 {
 2099 
 2100         mtx_unlock((struct mtx *)arg);
 2101 }
 2102 
 2103 static void
 2104 knlist_mtx_assert_locked(void *arg)
 2105 {
 2106 
 2107         mtx_assert((struct mtx *)arg, MA_OWNED);
 2108 }
 2109 
 2110 static void
 2111 knlist_mtx_assert_unlocked(void *arg)
 2112 {
 2113 
 2114         mtx_assert((struct mtx *)arg, MA_NOTOWNED);
 2115 }
 2116 
 2117 static void
 2118 knlist_rw_rlock(void *arg)
 2119 {
 2120 
 2121         rw_rlock((struct rwlock *)arg);
 2122 }
 2123 
 2124 static void
 2125 knlist_rw_runlock(void *arg)
 2126 {
 2127 
 2128         rw_runlock((struct rwlock *)arg);
 2129 }
 2130 
 2131 static void
 2132 knlist_rw_assert_locked(void *arg)
 2133 {
 2134 
 2135         rw_assert((struct rwlock *)arg, RA_LOCKED);
 2136 }
 2137 
 2138 static void
 2139 knlist_rw_assert_unlocked(void *arg)
 2140 {
 2141 
 2142         rw_assert((struct rwlock *)arg, RA_UNLOCKED);
 2143 }
 2144 
 2145 void
 2146 knlist_init(struct knlist *knl, void *lock, void (*kl_lock)(void *),
 2147     void (*kl_unlock)(void *),
 2148     void (*kl_assert_locked)(void *), void (*kl_assert_unlocked)(void *))
 2149 {
 2150 
 2151         if (lock == NULL)
 2152                 knl->kl_lockarg = &knlist_lock;
 2153         else
 2154                 knl->kl_lockarg = lock;
 2155 
 2156         if (kl_lock == NULL)
 2157                 knl->kl_lock = knlist_mtx_lock;
 2158         else
 2159                 knl->kl_lock = kl_lock;
 2160         if (kl_unlock == NULL)
 2161                 knl->kl_unlock = knlist_mtx_unlock;
 2162         else
 2163                 knl->kl_unlock = kl_unlock;
 2164         if (kl_assert_locked == NULL)
 2165                 knl->kl_assert_locked = knlist_mtx_assert_locked;
 2166         else
 2167                 knl->kl_assert_locked = kl_assert_locked;
 2168         if (kl_assert_unlocked == NULL)
 2169                 knl->kl_assert_unlocked = knlist_mtx_assert_unlocked;
 2170         else
 2171                 knl->kl_assert_unlocked = kl_assert_unlocked;
 2172 
 2173         SLIST_INIT(&knl->kl_list);
 2174 }
 2175 
 2176 void
 2177 knlist_init_mtx(struct knlist *knl, struct mtx *lock)
 2178 {
 2179 
 2180         knlist_init(knl, lock, NULL, NULL, NULL, NULL);
 2181 }
 2182 
 2183 void
 2184 knlist_init_rw_reader(struct knlist *knl, struct rwlock *lock)
 2185 {
 2186 
 2187         knlist_init(knl, lock, knlist_rw_rlock, knlist_rw_runlock,
 2188             knlist_rw_assert_locked, knlist_rw_assert_unlocked);
 2189 }
 2190 
 2191 void
 2192 knlist_destroy(struct knlist *knl)
 2193 {
 2194 
 2195         KASSERT(KNLIST_EMPTY(knl),
 2196             ("destroying knlist %p with knotes on it", knl));
 2197 }
 2198 
 2199 /*
 2200  * Even if we are locked, we may need to drop the lock to allow any influx
 2201  * knotes time to "settle".
 2202  */
 2203 void
 2204 knlist_cleardel(struct knlist *knl, struct thread *td, int islocked, int killkn)
 2205 {
 2206         struct knote *kn, *kn2;
 2207         struct kqueue *kq;
 2208 
 2209         if (islocked)
 2210                 KNL_ASSERT_LOCKED(knl);
 2211         else {
 2212                 KNL_ASSERT_UNLOCKED(knl);
 2213 again:          /* need to reacquire lock since we have dropped it */
 2214                 knl->kl_lock(knl->kl_lockarg);
 2215         }
 2216 
 2217         SLIST_FOREACH_SAFE(kn, &knl->kl_list, kn_selnext, kn2) {
 2218                 kq = kn->kn_kq;
 2219                 KQ_LOCK(kq);
 2220                 if ((kn->kn_status & KN_INFLUX)) {
 2221                         KQ_UNLOCK(kq);
 2222                         continue;
 2223                 }
 2224                 knlist_remove_kq(knl, kn, 1, 1);
 2225                 if (killkn) {
 2226                         kn->kn_status |= KN_INFLUX | KN_DETACHED;
 2227                         KQ_UNLOCK(kq);
 2228                         knote_drop(kn, td);
 2229                 } else {
 2230                         /* Make sure cleared knotes disappear soon */
 2231                         kn->kn_flags |= (EV_EOF | EV_ONESHOT);
 2232                         KQ_UNLOCK(kq);
 2233                 }
 2234                 kq = NULL;
 2235         }
 2236 
 2237         if (!SLIST_EMPTY(&knl->kl_list)) {
 2238                 /* there are still KN_INFLUX remaining */
 2239                 kn = SLIST_FIRST(&knl->kl_list);
 2240                 kq = kn->kn_kq;
 2241                 KQ_LOCK(kq);
 2242                 KASSERT(kn->kn_status & KN_INFLUX,
 2243                     ("knote removed w/o list lock"));
 2244                 knl->kl_unlock(knl->kl_lockarg);
 2245                 kq->kq_state |= KQ_FLUXWAIT;
 2246                 msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqkclr", 0);
 2247                 kq = NULL;
 2248                 goto again;
 2249         }
 2250 
 2251         if (islocked)
 2252                 KNL_ASSERT_LOCKED(knl);
 2253         else {
 2254                 knl->kl_unlock(knl->kl_lockarg);
 2255                 KNL_ASSERT_UNLOCKED(knl);
 2256         }
 2257 }
 2258 
 2259 /*
 2260  * Remove all knotes referencing a specified fd must be called with FILEDESC
 2261  * lock.  This prevents a race where a new fd comes along and occupies the
 2262  * entry and we attach a knote to the fd.
 2263  */
 2264 void
 2265 knote_fdclose(struct thread *td, int fd)
 2266 {
 2267         struct filedesc *fdp = td->td_proc->p_fd;
 2268         struct kqueue *kq;
 2269         struct knote *kn;
 2270         int influx;
 2271 
 2272         FILEDESC_XLOCK_ASSERT(fdp);
 2273 
 2274         /*
 2275          * We shouldn't have to worry about new kevents appearing on fd
 2276          * since filedesc is locked.
 2277          */
 2278         TAILQ_FOREACH(kq, &fdp->fd_kqlist, kq_list) {
 2279                 KQ_LOCK(kq);
 2280 
 2281 again:
 2282                 influx = 0;
 2283                 while (kq->kq_knlistsize > fd &&
 2284                     (kn = SLIST_FIRST(&kq->kq_knlist[fd])) != NULL) {
 2285                         if (kn->kn_status & KN_INFLUX) {
 2286                                 /* someone else might be waiting on our knote */
 2287                                 if (influx)
 2288                                         wakeup(kq);
 2289                                 kq->kq_state |= KQ_FLUXWAIT;
 2290                                 msleep(kq, &kq->kq_lock, PSOCK, "kqflxwt", 0);
 2291                                 goto again;
 2292                         }
 2293                         kn->kn_status |= KN_INFLUX;
 2294                         KQ_UNLOCK(kq);
 2295                         if (!(kn->kn_status & KN_DETACHED))
 2296                                 kn->kn_fop->f_detach(kn);
 2297                         knote_drop(kn, td);
 2298                         influx = 1;
 2299                         KQ_LOCK(kq);
 2300                 }
 2301                 KQ_UNLOCK_FLUX(kq);
 2302         }
 2303 }
 2304 
 2305 static int
 2306 knote_attach(struct knote *kn, struct kqueue *kq)
 2307 {
 2308         struct klist *list;
 2309 
 2310         KASSERT(kn->kn_status & KN_INFLUX, ("knote not marked INFLUX"));
 2311         KQ_OWNED(kq);
 2312 
 2313         if (kn->kn_fop->f_isfd) {
 2314                 if (kn->kn_id >= kq->kq_knlistsize)
 2315                         return (ENOMEM);
 2316                 list = &kq->kq_knlist[kn->kn_id];
 2317         } else {
 2318                 if (kq->kq_knhash == NULL)
 2319                         return (ENOMEM);
 2320                 list = &kq->kq_knhash[KN_HASH(kn->kn_id, kq->kq_knhashmask)];
 2321         }
 2322         SLIST_INSERT_HEAD(list, kn, kn_link);
 2323         return (0);
 2324 }
 2325 
 2326 /*
 2327  * knote must already have been detached using the f_detach method.
 2328  * no lock need to be held, it is assumed that the KN_INFLUX flag is set
 2329  * to prevent other removal.
 2330  */
 2331 static void
 2332 knote_drop(struct knote *kn, struct thread *td)
 2333 {
 2334         struct kqueue *kq;
 2335         struct klist *list;
 2336 
 2337         kq = kn->kn_kq;
 2338 
 2339         KQ_NOTOWNED(kq);
 2340         KASSERT((kn->kn_status & KN_INFLUX) == KN_INFLUX,
 2341             ("knote_drop called without KN_INFLUX set in kn_status"));
 2342 
 2343         KQ_LOCK(kq);
 2344         if (kn->kn_fop->f_isfd)
 2345                 list = &kq->kq_knlist[kn->kn_id];
 2346         else
 2347                 list = &kq->kq_knhash[KN_HASH(kn->kn_id, kq->kq_knhashmask)];
 2348 
 2349         if (!SLIST_EMPTY(list))
 2350                 SLIST_REMOVE(list, kn, knote, kn_link);
 2351         if (kn->kn_status & KN_QUEUED)
 2352                 knote_dequeue(kn);
 2353         KQ_UNLOCK_FLUX(kq);
 2354 
 2355         if (kn->kn_fop->f_isfd) {
 2356                 fdrop(kn->kn_fp, td);
 2357                 kn->kn_fp = NULL;
 2358         }
 2359         kqueue_fo_release(kn->kn_kevent.filter);
 2360         kn->kn_fop = NULL;
 2361         knote_free(kn);
 2362 }
 2363 
 2364 static void
 2365 knote_enqueue(struct knote *kn)
 2366 {
 2367         struct kqueue *kq = kn->kn_kq;
 2368 
 2369         KQ_OWNED(kn->kn_kq);
 2370         KASSERT((kn->kn_status & KN_QUEUED) == 0, ("knote already queued"));
 2371 
 2372         TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
 2373         kn->kn_status |= KN_QUEUED;
 2374         kq->kq_count++;
 2375         kqueue_wakeup(kq);
 2376 }
 2377 
 2378 static void
 2379 knote_dequeue(struct knote *kn)
 2380 {
 2381         struct kqueue *kq = kn->kn_kq;
 2382 
 2383         KQ_OWNED(kn->kn_kq);
 2384         KASSERT(kn->kn_status & KN_QUEUED, ("knote not queued"));
 2385 
 2386         TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
 2387         kn->kn_status &= ~KN_QUEUED;
 2388         kq->kq_count--;
 2389 }
 2390 
 2391 static void
 2392 knote_init(void)
 2393 {
 2394 
 2395         knote_zone = uma_zcreate("KNOTE", sizeof(struct knote), NULL, NULL,
 2396             NULL, NULL, UMA_ALIGN_PTR, 0);
 2397 }
 2398 SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_ANY, knote_init, NULL);
 2399 
 2400 static struct knote *
 2401 knote_alloc(int waitok)
 2402 {
 2403         return ((struct knote *)uma_zalloc(knote_zone,
 2404             (waitok ? M_WAITOK : M_NOWAIT)|M_ZERO));
 2405 }
 2406 
 2407 static void
 2408 knote_free(struct knote *kn)
 2409 {
 2410         if (kn != NULL)
 2411                 uma_zfree(knote_zone, kn);
 2412 }
 2413 
 2414 /*
 2415  * Register the kev w/ the kq specified by fd.
 2416  */
 2417 int 
 2418 kqfd_register(int fd, struct kevent *kev, struct thread *td, int waitok)
 2419 {
 2420         struct kqueue *kq;
 2421         struct file *fp;
 2422         cap_rights_t rights;
 2423         int error;
 2424 
 2425         error = fget(td, fd, cap_rights_init(&rights, CAP_KQUEUE_CHANGE), &fp);
 2426         if (error != 0)
 2427                 return (error);
 2428         if ((error = kqueue_acquire(fp, &kq)) != 0)
 2429                 goto noacquire;
 2430 
 2431         error = kqueue_register(kq, kev, td, waitok);
 2432         kqueue_release(kq, 0);
 2433 
 2434 noacquire:
 2435         fdrop(fp, td);
 2436         return (error);
 2437 }

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