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

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    1 /*-
    2  * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. Neither the name of the author nor the names of any co-contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 /*
   31  * Implementation of sleep queues used to hold queue of threads blocked on
   32  * a wait channel.  Sleep queues different from turnstiles in that wait
   33  * channels are not owned by anyone, so there is no priority propagation.
   34  * Sleep queues can also provide a timeout and can also be interrupted by
   35  * signals.  That said, there are several similarities between the turnstile
   36  * and sleep queue implementations.  (Note: turnstiles were implemented
   37  * first.)  For example, both use a hash table of the same size where each
   38  * bucket is referred to as a "chain" that contains both a spin lock and
   39  * a linked list of queues.  An individual queue is located by using a hash
   40  * to pick a chain, locking the chain, and then walking the chain searching
   41  * for the queue.  This means that a wait channel object does not need to
   42  * embed it's queue head just as locks do not embed their turnstile queue
   43  * head.  Threads also carry around a sleep queue that they lend to the
   44  * wait channel when blocking.  Just as in turnstiles, the queue includes
   45  * a free list of the sleep queues of other threads blocked on the same
   46  * wait channel in the case of multiple waiters.
   47  *
   48  * Some additional functionality provided by sleep queues include the
   49  * ability to set a timeout.  The timeout is managed using a per-thread
   50  * callout that resumes a thread if it is asleep.  A thread may also
   51  * catch signals while it is asleep (aka an interruptible sleep).  The
   52  * signal code uses sleepq_abort() to interrupt a sleeping thread.  Finally,
   53  * sleep queues also provide some extra assertions.  One is not allowed to
   54  * mix the sleep/wakeup and cv APIs for a given wait channel.  Also, one
   55  * must consistently use the same lock to synchronize with a wait channel,
   56  * though this check is currently only a warning for sleep/wakeup due to
   57  * pre-existing abuse of that API.  The same lock must also be held when
   58  * awakening threads, though that is currently only enforced for condition
   59  * variables.
   60  */
   61 
   62 #include <sys/cdefs.h>
   63 __FBSDID("$FreeBSD: releng/9.0/sys/kern/subr_sleepqueue.c 217916 2011-01-27 00:34:12Z mdf $");
   64 
   65 #include "opt_sleepqueue_profiling.h"
   66 #include "opt_ddb.h"
   67 #include "opt_sched.h"
   68 
   69 #include <sys/param.h>
   70 #include <sys/systm.h>
   71 #include <sys/lock.h>
   72 #include <sys/kernel.h>
   73 #include <sys/ktr.h>
   74 #include <sys/mutex.h>
   75 #include <sys/proc.h>
   76 #include <sys/sbuf.h>
   77 #include <sys/sched.h>
   78 #include <sys/signalvar.h>
   79 #include <sys/sleepqueue.h>
   80 #include <sys/sysctl.h>
   81 
   82 #include <vm/uma.h>
   83 
   84 #ifdef DDB
   85 #include <ddb/ddb.h>
   86 #endif
   87 
   88 /*
   89  * Constants for the hash table of sleep queue chains.  These constants are
   90  * the same ones that 4BSD (and possibly earlier versions of BSD) used.
   91  * Basically, we ignore the lower 8 bits of the address since most wait
   92  * channel pointers are aligned and only look at the next 7 bits for the
   93  * hash.  SC_TABLESIZE must be a power of two for SC_MASK to work properly.
   94  */
   95 #define SC_TABLESIZE    128                     /* Must be power of 2. */
   96 #define SC_MASK         (SC_TABLESIZE - 1)
   97 #define SC_SHIFT        8
   98 #define SC_HASH(wc)     (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
   99 #define SC_LOOKUP(wc)   &sleepq_chains[SC_HASH(wc)]
  100 #define NR_SLEEPQS      2
  101 /*
  102  * There two different lists of sleep queues.  Both lists are connected
  103  * via the sq_hash entries.  The first list is the sleep queue chain list
  104  * that a sleep queue is on when it is attached to a wait channel.  The
  105  * second list is the free list hung off of a sleep queue that is attached
  106  * to a wait channel.
  107  *
  108  * Each sleep queue also contains the wait channel it is attached to, the
  109  * list of threads blocked on that wait channel, flags specific to the
  110  * wait channel, and the lock used to synchronize with a wait channel.
  111  * The flags are used to catch mismatches between the various consumers
  112  * of the sleep queue API (e.g. sleep/wakeup and condition variables).
  113  * The lock pointer is only used when invariants are enabled for various
  114  * debugging checks.
  115  *
  116  * Locking key:
  117  *  c - sleep queue chain lock
  118  */
  119 struct sleepqueue {
  120         TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS];    /* (c) Blocked threads. */
  121         u_int sq_blockedcnt[NR_SLEEPQS];        /* (c) N. of blocked threads. */
  122         LIST_ENTRY(sleepqueue) sq_hash;         /* (c) Chain and free list. */
  123         LIST_HEAD(, sleepqueue) sq_free;        /* (c) Free queues. */
  124         void    *sq_wchan;                      /* (c) Wait channel. */
  125         int     sq_type;                        /* (c) Queue type. */
  126 #ifdef INVARIANTS
  127         struct lock_object *sq_lock;            /* (c) Associated lock. */
  128 #endif
  129 };
  130 
  131 struct sleepqueue_chain {
  132         LIST_HEAD(, sleepqueue) sc_queues;      /* List of sleep queues. */
  133         struct mtx sc_lock;                     /* Spin lock for this chain. */
  134 #ifdef SLEEPQUEUE_PROFILING
  135         u_int   sc_depth;                       /* Length of sc_queues. */
  136         u_int   sc_max_depth;                   /* Max length of sc_queues. */
  137 #endif
  138 };
  139 
  140 #ifdef SLEEPQUEUE_PROFILING
  141 u_int sleepq_max_depth;
  142 SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
  143 SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
  144     "sleepq chain stats");
  145 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
  146     0, "maxmimum depth achieved of a single chain");
  147 
  148 static void     sleepq_profile(const char *wmesg);
  149 static int      prof_enabled;
  150 #endif
  151 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
  152 static uma_zone_t sleepq_zone;
  153 
  154 /*
  155  * Prototypes for non-exported routines.
  156  */
  157 static int      sleepq_catch_signals(void *wchan, int pri);
  158 static int      sleepq_check_signals(void);
  159 static int      sleepq_check_timeout(void);
  160 #ifdef INVARIANTS
  161 static void     sleepq_dtor(void *mem, int size, void *arg);
  162 #endif
  163 static int      sleepq_init(void *mem, int size, int flags);
  164 static int      sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
  165                     int pri);
  166 static void     sleepq_switch(void *wchan, int pri);
  167 static void     sleepq_timeout(void *arg);
  168 
  169 /*
  170  * Early initialization of sleep queues that is called from the sleepinit()
  171  * SYSINIT.
  172  */
  173 void
  174 init_sleepqueues(void)
  175 {
  176 #ifdef SLEEPQUEUE_PROFILING
  177         struct sysctl_oid *chain_oid;
  178         char chain_name[10];
  179 #endif
  180         int i;
  181 
  182         for (i = 0; i < SC_TABLESIZE; i++) {
  183                 LIST_INIT(&sleepq_chains[i].sc_queues);
  184                 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
  185                     MTX_SPIN | MTX_RECURSE);
  186 #ifdef SLEEPQUEUE_PROFILING
  187                 snprintf(chain_name, sizeof(chain_name), "%d", i);
  188                 chain_oid = SYSCTL_ADD_NODE(NULL, 
  189                     SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
  190                     chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
  191                 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
  192                     "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
  193                 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
  194                     "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
  195                     NULL);
  196 #endif
  197         }
  198         sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
  199 #ifdef INVARIANTS
  200             NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
  201 #else
  202             NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
  203 #endif
  204         
  205         thread0.td_sleepqueue = sleepq_alloc();
  206 }
  207 
  208 /*
  209  * Get a sleep queue for a new thread.
  210  */
  211 struct sleepqueue *
  212 sleepq_alloc(void)
  213 {
  214 
  215         return (uma_zalloc(sleepq_zone, M_WAITOK));
  216 }
  217 
  218 /*
  219  * Free a sleep queue when a thread is destroyed.
  220  */
  221 void
  222 sleepq_free(struct sleepqueue *sq)
  223 {
  224 
  225         uma_zfree(sleepq_zone, sq);
  226 }
  227 
  228 /*
  229  * Lock the sleep queue chain associated with the specified wait channel.
  230  */
  231 void
  232 sleepq_lock(void *wchan)
  233 {
  234         struct sleepqueue_chain *sc;
  235 
  236         sc = SC_LOOKUP(wchan);
  237         mtx_lock_spin(&sc->sc_lock);
  238 }
  239 
  240 /*
  241  * Look up the sleep queue associated with a given wait channel in the hash
  242  * table locking the associated sleep queue chain.  If no queue is found in
  243  * the table, NULL is returned.
  244  */
  245 struct sleepqueue *
  246 sleepq_lookup(void *wchan)
  247 {
  248         struct sleepqueue_chain *sc;
  249         struct sleepqueue *sq;
  250 
  251         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  252         sc = SC_LOOKUP(wchan);
  253         mtx_assert(&sc->sc_lock, MA_OWNED);
  254         LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
  255                 if (sq->sq_wchan == wchan)
  256                         return (sq);
  257         return (NULL);
  258 }
  259 
  260 /*
  261  * Unlock the sleep queue chain associated with a given wait channel.
  262  */
  263 void
  264 sleepq_release(void *wchan)
  265 {
  266         struct sleepqueue_chain *sc;
  267 
  268         sc = SC_LOOKUP(wchan);
  269         mtx_unlock_spin(&sc->sc_lock);
  270 }
  271 
  272 /*
  273  * Places the current thread on the sleep queue for the specified wait
  274  * channel.  If INVARIANTS is enabled, then it associates the passed in
  275  * lock with the sleepq to make sure it is held when that sleep queue is
  276  * woken up.
  277  */
  278 void
  279 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
  280     int queue)
  281 {
  282         struct sleepqueue_chain *sc;
  283         struct sleepqueue *sq;
  284         struct thread *td;
  285 
  286         td = curthread;
  287         sc = SC_LOOKUP(wchan);
  288         mtx_assert(&sc->sc_lock, MA_OWNED);
  289         MPASS(td->td_sleepqueue != NULL);
  290         MPASS(wchan != NULL);
  291         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  292 
  293         /* If this thread is not allowed to sleep, die a horrible death. */
  294         KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
  295             ("Trying sleep, but thread marked as sleeping prohibited"));
  296 
  297         /* Look up the sleep queue associated with the wait channel 'wchan'. */
  298         sq = sleepq_lookup(wchan);
  299 
  300         /*
  301          * If the wait channel does not already have a sleep queue, use
  302          * this thread's sleep queue.  Otherwise, insert the current thread
  303          * into the sleep queue already in use by this wait channel.
  304          */
  305         if (sq == NULL) {
  306 #ifdef INVARIANTS
  307                 int i;
  308 
  309                 sq = td->td_sleepqueue;
  310                 for (i = 0; i < NR_SLEEPQS; i++) {
  311                         KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
  312                             ("thread's sleep queue %d is not empty", i));
  313                         KASSERT(sq->sq_blockedcnt[i] == 0,
  314                             ("thread's sleep queue %d count mismatches", i));
  315                 }
  316                 KASSERT(LIST_EMPTY(&sq->sq_free),
  317                     ("thread's sleep queue has a non-empty free list"));
  318                 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
  319                 sq->sq_lock = lock;
  320 #endif
  321 #ifdef SLEEPQUEUE_PROFILING
  322                 sc->sc_depth++;
  323                 if (sc->sc_depth > sc->sc_max_depth) {
  324                         sc->sc_max_depth = sc->sc_depth;
  325                         if (sc->sc_max_depth > sleepq_max_depth)
  326                                 sleepq_max_depth = sc->sc_max_depth;
  327                 }
  328 #endif
  329                 sq = td->td_sleepqueue;
  330                 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
  331                 sq->sq_wchan = wchan;
  332                 sq->sq_type = flags & SLEEPQ_TYPE;
  333         } else {
  334                 MPASS(wchan == sq->sq_wchan);
  335                 MPASS(lock == sq->sq_lock);
  336                 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
  337                 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
  338         }
  339         thread_lock(td);
  340         TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
  341         sq->sq_blockedcnt[queue]++;
  342         td->td_sleepqueue = NULL;
  343         td->td_sqqueue = queue;
  344         td->td_wchan = wchan;
  345         td->td_wmesg = wmesg;
  346         if (flags & SLEEPQ_INTERRUPTIBLE) {
  347                 td->td_flags |= TDF_SINTR;
  348                 td->td_flags &= ~TDF_SLEEPABORT;
  349                 if (flags & SLEEPQ_STOP_ON_BDRY)
  350                         td->td_flags |= TDF_SBDRY;
  351         }
  352         thread_unlock(td);
  353 }
  354 
  355 /*
  356  * Sets a timeout that will remove the current thread from the specified
  357  * sleep queue after timo ticks if the thread has not already been awakened.
  358  */
  359 void
  360 sleepq_set_timeout(void *wchan, int timo)
  361 {
  362         struct sleepqueue_chain *sc;
  363         struct thread *td;
  364 
  365         td = curthread;
  366         sc = SC_LOOKUP(wchan);
  367         mtx_assert(&sc->sc_lock, MA_OWNED);
  368         MPASS(TD_ON_SLEEPQ(td));
  369         MPASS(td->td_sleepqueue == NULL);
  370         MPASS(wchan != NULL);
  371         callout_reset_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td);
  372 }
  373 
  374 /*
  375  * Return the number of actual sleepers for the specified queue.
  376  */
  377 u_int
  378 sleepq_sleepcnt(void *wchan, int queue)
  379 {
  380         struct sleepqueue *sq;
  381 
  382         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  383         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  384         sq = sleepq_lookup(wchan);
  385         if (sq == NULL)
  386                 return (0);
  387         return (sq->sq_blockedcnt[queue]);
  388 }
  389 
  390 /*
  391  * Marks the pending sleep of the current thread as interruptible and
  392  * makes an initial check for pending signals before putting a thread
  393  * to sleep. Enters and exits with the thread lock held.  Thread lock
  394  * may have transitioned from the sleepq lock to a run lock.
  395  */
  396 static int
  397 sleepq_catch_signals(void *wchan, int pri)
  398 {
  399         struct sleepqueue_chain *sc;
  400         struct sleepqueue *sq;
  401         struct thread *td;
  402         struct proc *p;
  403         struct sigacts *ps;
  404         int sig, ret, stop_allowed;
  405 
  406         td = curthread;
  407         p = curproc;
  408         sc = SC_LOOKUP(wchan);
  409         mtx_assert(&sc->sc_lock, MA_OWNED);
  410         MPASS(wchan != NULL);
  411         if ((td->td_pflags & TDP_WAKEUP) != 0) {
  412                 td->td_pflags &= ~TDP_WAKEUP;
  413                 ret = EINTR;
  414                 thread_lock(td);
  415                 goto out;
  416         }
  417 
  418         /*
  419          * See if there are any pending signals for this thread.  If not
  420          * we can switch immediately.  Otherwise do the signal processing
  421          * directly.
  422          */
  423         thread_lock(td);
  424         if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
  425                 sleepq_switch(wchan, pri);
  426                 return (0);
  427         }
  428         stop_allowed = (td->td_flags & TDF_SBDRY) ? SIG_STOP_NOT_ALLOWED :
  429             SIG_STOP_ALLOWED;
  430         thread_unlock(td);
  431         mtx_unlock_spin(&sc->sc_lock);
  432         CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
  433                 (void *)td, (long)p->p_pid, td->td_name);
  434         PROC_LOCK(p);
  435         ps = p->p_sigacts;
  436         mtx_lock(&ps->ps_mtx);
  437         sig = cursig(td, stop_allowed);
  438         if (sig == 0) {
  439                 mtx_unlock(&ps->ps_mtx);
  440                 ret = thread_suspend_check(1);
  441                 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
  442         } else {
  443                 if (SIGISMEMBER(ps->ps_sigintr, sig))
  444                         ret = EINTR;
  445                 else
  446                         ret = ERESTART;
  447                 mtx_unlock(&ps->ps_mtx);
  448         }
  449         /*
  450          * Lock the per-process spinlock prior to dropping the PROC_LOCK
  451          * to avoid a signal delivery race.  PROC_LOCK, PROC_SLOCK, and
  452          * thread_lock() are currently held in tdsendsignal().
  453          */
  454         PROC_SLOCK(p);
  455         mtx_lock_spin(&sc->sc_lock);
  456         PROC_UNLOCK(p);
  457         thread_lock(td);
  458         PROC_SUNLOCK(p);
  459         if (ret == 0) {
  460                 sleepq_switch(wchan, pri);
  461                 return (0);
  462         }
  463 out:
  464         /*
  465          * There were pending signals and this thread is still
  466          * on the sleep queue, remove it from the sleep queue.
  467          */
  468         if (TD_ON_SLEEPQ(td)) {
  469                 sq = sleepq_lookup(wchan);
  470                 if (sleepq_resume_thread(sq, td, 0)) {
  471 #ifdef INVARIANTS
  472                         /*
  473                          * This thread hasn't gone to sleep yet, so it
  474                          * should not be swapped out.
  475                          */
  476                         panic("not waking up swapper");
  477 #endif
  478                 }
  479         }
  480         mtx_unlock_spin(&sc->sc_lock);
  481         MPASS(td->td_lock != &sc->sc_lock);
  482         return (ret);
  483 }
  484 
  485 /*
  486  * Switches to another thread if we are still asleep on a sleep queue.
  487  * Returns with thread lock.
  488  */
  489 static void
  490 sleepq_switch(void *wchan, int pri)
  491 {
  492         struct sleepqueue_chain *sc;
  493         struct sleepqueue *sq;
  494         struct thread *td;
  495 
  496         td = curthread;
  497         sc = SC_LOOKUP(wchan);
  498         mtx_assert(&sc->sc_lock, MA_OWNED);
  499         THREAD_LOCK_ASSERT(td, MA_OWNED);
  500 
  501         /* 
  502          * If we have a sleep queue, then we've already been woken up, so
  503          * just return.
  504          */
  505         if (td->td_sleepqueue != NULL) {
  506                 mtx_unlock_spin(&sc->sc_lock);
  507                 return;
  508         }
  509 
  510         /*
  511          * If TDF_TIMEOUT is set, then our sleep has been timed out
  512          * already but we are still on the sleep queue, so dequeue the
  513          * thread and return.
  514          */
  515         if (td->td_flags & TDF_TIMEOUT) {
  516                 MPASS(TD_ON_SLEEPQ(td));
  517                 sq = sleepq_lookup(wchan);
  518                 if (sleepq_resume_thread(sq, td, 0)) {
  519 #ifdef INVARIANTS
  520                         /*
  521                          * This thread hasn't gone to sleep yet, so it
  522                          * should not be swapped out.
  523                          */
  524                         panic("not waking up swapper");
  525 #endif
  526                 }
  527                 mtx_unlock_spin(&sc->sc_lock);
  528                 return;         
  529         }
  530 #ifdef SLEEPQUEUE_PROFILING
  531         if (prof_enabled)
  532                 sleepq_profile(td->td_wmesg);
  533 #endif
  534         MPASS(td->td_sleepqueue == NULL);
  535         sched_sleep(td, pri);
  536         thread_lock_set(td, &sc->sc_lock);
  537         TD_SET_SLEEPING(td);
  538         mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
  539         KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
  540         CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
  541             (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
  542 }
  543 
  544 /*
  545  * Check to see if we timed out.
  546  */
  547 static int
  548 sleepq_check_timeout(void)
  549 {
  550         struct thread *td;
  551 
  552         td = curthread;
  553         THREAD_LOCK_ASSERT(td, MA_OWNED);
  554 
  555         /*
  556          * If TDF_TIMEOUT is set, we timed out.
  557          */
  558         if (td->td_flags & TDF_TIMEOUT) {
  559                 td->td_flags &= ~TDF_TIMEOUT;
  560                 return (EWOULDBLOCK);
  561         }
  562 
  563         /*
  564          * If TDF_TIMOFAIL is set, the timeout ran after we had
  565          * already been woken up.
  566          */
  567         if (td->td_flags & TDF_TIMOFAIL)
  568                 td->td_flags &= ~TDF_TIMOFAIL;
  569 
  570         /*
  571          * If callout_stop() fails, then the timeout is running on
  572          * another CPU, so synchronize with it to avoid having it
  573          * accidentally wake up a subsequent sleep.
  574          */
  575         else if (callout_stop(&td->td_slpcallout) == 0) {
  576                 td->td_flags |= TDF_TIMEOUT;
  577                 TD_SET_SLEEPING(td);
  578                 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
  579         }
  580         return (0);
  581 }
  582 
  583 /*
  584  * Check to see if we were awoken by a signal.
  585  */
  586 static int
  587 sleepq_check_signals(void)
  588 {
  589         struct thread *td;
  590 
  591         td = curthread;
  592         THREAD_LOCK_ASSERT(td, MA_OWNED);
  593 
  594         /* We are no longer in an interruptible sleep. */
  595         if (td->td_flags & TDF_SINTR)
  596                 td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
  597 
  598         if (td->td_flags & TDF_SLEEPABORT) {
  599                 td->td_flags &= ~TDF_SLEEPABORT;
  600                 return (td->td_intrval);
  601         }
  602 
  603         return (0);
  604 }
  605 
  606 /*
  607  * Block the current thread until it is awakened from its sleep queue.
  608  */
  609 void
  610 sleepq_wait(void *wchan, int pri)
  611 {
  612         struct thread *td;
  613 
  614         td = curthread;
  615         MPASS(!(td->td_flags & TDF_SINTR));
  616         thread_lock(td);
  617         sleepq_switch(wchan, pri);
  618         thread_unlock(td);
  619 }
  620 
  621 /*
  622  * Block the current thread until it is awakened from its sleep queue
  623  * or it is interrupted by a signal.
  624  */
  625 int
  626 sleepq_wait_sig(void *wchan, int pri)
  627 {
  628         int rcatch;
  629         int rval;
  630 
  631         rcatch = sleepq_catch_signals(wchan, pri);
  632         rval = sleepq_check_signals();
  633         thread_unlock(curthread);
  634         if (rcatch)
  635                 return (rcatch);
  636         return (rval);
  637 }
  638 
  639 /*
  640  * Block the current thread until it is awakened from its sleep queue
  641  * or it times out while waiting.
  642  */
  643 int
  644 sleepq_timedwait(void *wchan, int pri)
  645 {
  646         struct thread *td;
  647         int rval;
  648 
  649         td = curthread;
  650         MPASS(!(td->td_flags & TDF_SINTR));
  651         thread_lock(td);
  652         sleepq_switch(wchan, pri);
  653         rval = sleepq_check_timeout();
  654         thread_unlock(td);
  655 
  656         return (rval);
  657 }
  658 
  659 /*
  660  * Block the current thread until it is awakened from its sleep queue,
  661  * it is interrupted by a signal, or it times out waiting to be awakened.
  662  */
  663 int
  664 sleepq_timedwait_sig(void *wchan, int pri)
  665 {
  666         int rcatch, rvalt, rvals;
  667 
  668         rcatch = sleepq_catch_signals(wchan, pri);
  669         rvalt = sleepq_check_timeout();
  670         rvals = sleepq_check_signals();
  671         thread_unlock(curthread);
  672         if (rcatch)
  673                 return (rcatch);
  674         if (rvals)
  675                 return (rvals);
  676         return (rvalt);
  677 }
  678 
  679 /*
  680  * Returns the type of sleepqueue given a waitchannel.
  681  */
  682 int
  683 sleepq_type(void *wchan)
  684 {
  685         struct sleepqueue *sq;
  686         int type;
  687 
  688         MPASS(wchan != NULL);
  689 
  690         sleepq_lock(wchan);
  691         sq = sleepq_lookup(wchan);
  692         if (sq == NULL) {
  693                 sleepq_release(wchan);
  694                 return (-1);
  695         }
  696         type = sq->sq_type;
  697         sleepq_release(wchan);
  698         return (type);
  699 }
  700 
  701 /*
  702  * Removes a thread from a sleep queue and makes it
  703  * runnable.
  704  */
  705 static int
  706 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
  707 {
  708         struct sleepqueue_chain *sc;
  709 
  710         MPASS(td != NULL);
  711         MPASS(sq->sq_wchan != NULL);
  712         MPASS(td->td_wchan == sq->sq_wchan);
  713         MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
  714         THREAD_LOCK_ASSERT(td, MA_OWNED);
  715         sc = SC_LOOKUP(sq->sq_wchan);
  716         mtx_assert(&sc->sc_lock, MA_OWNED);
  717 
  718         /* Remove the thread from the queue. */
  719         sq->sq_blockedcnt[td->td_sqqueue]--;
  720         TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
  721 
  722         /*
  723          * Get a sleep queue for this thread.  If this is the last waiter,
  724          * use the queue itself and take it out of the chain, otherwise,
  725          * remove a queue from the free list.
  726          */
  727         if (LIST_EMPTY(&sq->sq_free)) {
  728                 td->td_sleepqueue = sq;
  729 #ifdef INVARIANTS
  730                 sq->sq_wchan = NULL;
  731 #endif
  732 #ifdef SLEEPQUEUE_PROFILING
  733                 sc->sc_depth--;
  734 #endif
  735         } else
  736                 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
  737         LIST_REMOVE(td->td_sleepqueue, sq_hash);
  738 
  739         td->td_wmesg = NULL;
  740         td->td_wchan = NULL;
  741         td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
  742 
  743         CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
  744             (void *)td, (long)td->td_proc->p_pid, td->td_name);
  745 
  746         /* Adjust priority if requested. */
  747         MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
  748         if (pri != 0 && td->td_priority > pri &&
  749             PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
  750                 sched_prio(td, pri);
  751 
  752         /*
  753          * Note that thread td might not be sleeping if it is running
  754          * sleepq_catch_signals() on another CPU or is blocked on its
  755          * proc lock to check signals.  There's no need to mark the
  756          * thread runnable in that case.
  757          */
  758         if (TD_IS_SLEEPING(td)) {
  759                 TD_CLR_SLEEPING(td);
  760                 return (setrunnable(td));
  761         }
  762         return (0);
  763 }
  764 
  765 #ifdef INVARIANTS
  766 /*
  767  * UMA zone item deallocator.
  768  */
  769 static void
  770 sleepq_dtor(void *mem, int size, void *arg)
  771 {
  772         struct sleepqueue *sq;
  773         int i;
  774 
  775         sq = mem;
  776         for (i = 0; i < NR_SLEEPQS; i++) {
  777                 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
  778                 MPASS(sq->sq_blockedcnt[i] == 0);
  779         }
  780 }
  781 #endif
  782 
  783 /*
  784  * UMA zone item initializer.
  785  */
  786 static int
  787 sleepq_init(void *mem, int size, int flags)
  788 {
  789         struct sleepqueue *sq;
  790         int i;
  791 
  792         bzero(mem, size);
  793         sq = mem;
  794         for (i = 0; i < NR_SLEEPQS; i++) {
  795                 TAILQ_INIT(&sq->sq_blocked[i]);
  796                 sq->sq_blockedcnt[i] = 0;
  797         }
  798         LIST_INIT(&sq->sq_free);
  799         return (0);
  800 }
  801 
  802 /*
  803  * Find the highest priority thread sleeping on a wait channel and resume it.
  804  */
  805 int
  806 sleepq_signal(void *wchan, int flags, int pri, int queue)
  807 {
  808         struct sleepqueue *sq;
  809         struct thread *td, *besttd;
  810         int wakeup_swapper;
  811 
  812         CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
  813         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  814         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  815         sq = sleepq_lookup(wchan);
  816         if (sq == NULL)
  817                 return (0);
  818         KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
  819             ("%s: mismatch between sleep/wakeup and cv_*", __func__));
  820 
  821         /*
  822          * Find the highest priority thread on the queue.  If there is a
  823          * tie, use the thread that first appears in the queue as it has
  824          * been sleeping the longest since threads are always added to
  825          * the tail of sleep queues.
  826          */
  827         besttd = NULL;
  828         TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
  829                 if (besttd == NULL || td->td_priority < besttd->td_priority)
  830                         besttd = td;
  831         }
  832         MPASS(besttd != NULL);
  833         thread_lock(besttd);
  834         wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
  835         thread_unlock(besttd);
  836         return (wakeup_swapper);
  837 }
  838 
  839 /*
  840  * Resume all threads sleeping on a specified wait channel.
  841  */
  842 int
  843 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
  844 {
  845         struct sleepqueue *sq;
  846         struct thread *td, *tdn;
  847         int wakeup_swapper;
  848 
  849         CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
  850         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  851         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  852         sq = sleepq_lookup(wchan);
  853         if (sq == NULL)
  854                 return (0);
  855         KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
  856             ("%s: mismatch between sleep/wakeup and cv_*", __func__));
  857 
  858         /* Resume all blocked threads on the sleep queue. */
  859         wakeup_swapper = 0;
  860         TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
  861                 thread_lock(td);
  862                 if (sleepq_resume_thread(sq, td, pri))
  863                         wakeup_swapper = 1;
  864                 thread_unlock(td);
  865         }
  866         return (wakeup_swapper);
  867 }
  868 
  869 /*
  870  * Time sleeping threads out.  When the timeout expires, the thread is
  871  * removed from the sleep queue and made runnable if it is still asleep.
  872  */
  873 static void
  874 sleepq_timeout(void *arg)
  875 {
  876         struct sleepqueue_chain *sc;
  877         struct sleepqueue *sq;
  878         struct thread *td;
  879         void *wchan;
  880         int wakeup_swapper;
  881 
  882         td = arg;
  883         wakeup_swapper = 0;
  884         CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
  885             (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
  886 
  887         /*
  888          * First, see if the thread is asleep and get the wait channel if
  889          * it is.
  890          */
  891         thread_lock(td);
  892         if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
  893                 wchan = td->td_wchan;
  894                 sc = SC_LOOKUP(wchan);
  895                 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
  896                 sq = sleepq_lookup(wchan);
  897                 MPASS(sq != NULL);
  898                 td->td_flags |= TDF_TIMEOUT;
  899                 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
  900                 thread_unlock(td);
  901                 if (wakeup_swapper)
  902                         kick_proc0();
  903                 return;
  904         }
  905 
  906         /*
  907          * If the thread is on the SLEEPQ but isn't sleeping yet, it
  908          * can either be on another CPU in between sleepq_add() and
  909          * one of the sleepq_*wait*() routines or it can be in
  910          * sleepq_catch_signals().
  911          */
  912         if (TD_ON_SLEEPQ(td)) {
  913                 td->td_flags |= TDF_TIMEOUT;
  914                 thread_unlock(td);
  915                 return;
  916         }
  917 
  918         /*
  919          * Now check for the edge cases.  First, if TDF_TIMEOUT is set,
  920          * then the other thread has already yielded to us, so clear
  921          * the flag and resume it.  If TDF_TIMEOUT is not set, then the
  922          * we know that the other thread is not on a sleep queue, but it
  923          * hasn't resumed execution yet.  In that case, set TDF_TIMOFAIL
  924          * to let it know that the timeout has already run and doesn't
  925          * need to be canceled.
  926          */
  927         if (td->td_flags & TDF_TIMEOUT) {
  928                 MPASS(TD_IS_SLEEPING(td));
  929                 td->td_flags &= ~TDF_TIMEOUT;
  930                 TD_CLR_SLEEPING(td);
  931                 wakeup_swapper = setrunnable(td);
  932         } else
  933                 td->td_flags |= TDF_TIMOFAIL;
  934         thread_unlock(td);
  935         if (wakeup_swapper)
  936                 kick_proc0();
  937 }
  938 
  939 /*
  940  * Resumes a specific thread from the sleep queue associated with a specific
  941  * wait channel if it is on that queue.
  942  */
  943 void
  944 sleepq_remove(struct thread *td, void *wchan)
  945 {
  946         struct sleepqueue *sq;
  947         int wakeup_swapper;
  948 
  949         /*
  950          * Look up the sleep queue for this wait channel, then re-check
  951          * that the thread is asleep on that channel, if it is not, then
  952          * bail.
  953          */
  954         MPASS(wchan != NULL);
  955         sleepq_lock(wchan);
  956         sq = sleepq_lookup(wchan);
  957         /*
  958          * We can not lock the thread here as it may be sleeping on a
  959          * different sleepq.  However, holding the sleepq lock for this
  960          * wchan can guarantee that we do not miss a wakeup for this
  961          * channel.  The asserts below will catch any false positives.
  962          */
  963         if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
  964                 sleepq_release(wchan);
  965                 return;
  966         }
  967         /* Thread is asleep on sleep queue sq, so wake it up. */
  968         thread_lock(td);
  969         MPASS(sq != NULL);
  970         MPASS(td->td_wchan == wchan);
  971         wakeup_swapper = sleepq_resume_thread(sq, td, 0);
  972         thread_unlock(td);
  973         sleepq_release(wchan);
  974         if (wakeup_swapper)
  975                 kick_proc0();
  976 }
  977 
  978 /*
  979  * Abort a thread as if an interrupt had occurred.  Only abort
  980  * interruptible waits (unfortunately it isn't safe to abort others).
  981  */
  982 int
  983 sleepq_abort(struct thread *td, int intrval)
  984 {
  985         struct sleepqueue *sq;
  986         void *wchan;
  987 
  988         THREAD_LOCK_ASSERT(td, MA_OWNED);
  989         MPASS(TD_ON_SLEEPQ(td));
  990         MPASS(td->td_flags & TDF_SINTR);
  991         MPASS(intrval == EINTR || intrval == ERESTART);
  992 
  993         /*
  994          * If the TDF_TIMEOUT flag is set, just leave. A
  995          * timeout is scheduled anyhow.
  996          */
  997         if (td->td_flags & TDF_TIMEOUT)
  998                 return (0);
  999 
 1000         CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
 1001             (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
 1002         td->td_intrval = intrval;
 1003         td->td_flags |= TDF_SLEEPABORT;
 1004         /*
 1005          * If the thread has not slept yet it will find the signal in
 1006          * sleepq_catch_signals() and call sleepq_resume_thread.  Otherwise
 1007          * we have to do it here.
 1008          */
 1009         if (!TD_IS_SLEEPING(td))
 1010                 return (0);
 1011         wchan = td->td_wchan;
 1012         MPASS(wchan != NULL);
 1013         sq = sleepq_lookup(wchan);
 1014         MPASS(sq != NULL);
 1015 
 1016         /* Thread is asleep on sleep queue sq, so wake it up. */
 1017         return (sleepq_resume_thread(sq, td, 0));
 1018 }
 1019 
 1020 #ifdef SLEEPQUEUE_PROFILING
 1021 #define SLEEPQ_PROF_LOCATIONS   1024
 1022 #define SLEEPQ_SBUFSIZE         512
 1023 struct sleepq_prof {
 1024         LIST_ENTRY(sleepq_prof) sp_link;
 1025         const char      *sp_wmesg;
 1026         long            sp_count;
 1027 };
 1028 
 1029 LIST_HEAD(sqphead, sleepq_prof);
 1030 
 1031 struct sqphead sleepq_prof_free;
 1032 struct sqphead sleepq_hash[SC_TABLESIZE];
 1033 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
 1034 static struct mtx sleepq_prof_lock;
 1035 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
 1036 
 1037 static void
 1038 sleepq_profile(const char *wmesg)
 1039 {
 1040         struct sleepq_prof *sp;
 1041 
 1042         mtx_lock_spin(&sleepq_prof_lock);
 1043         if (prof_enabled == 0)
 1044                 goto unlock;
 1045         LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
 1046                 if (sp->sp_wmesg == wmesg)
 1047                         goto done;
 1048         sp = LIST_FIRST(&sleepq_prof_free);
 1049         if (sp == NULL)
 1050                 goto unlock;
 1051         sp->sp_wmesg = wmesg;
 1052         LIST_REMOVE(sp, sp_link);
 1053         LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
 1054 done:
 1055         sp->sp_count++;
 1056 unlock:
 1057         mtx_unlock_spin(&sleepq_prof_lock);
 1058         return;
 1059 }
 1060 
 1061 static void
 1062 sleepq_prof_reset(void)
 1063 {
 1064         struct sleepq_prof *sp;
 1065         int enabled;
 1066         int i;
 1067 
 1068         mtx_lock_spin(&sleepq_prof_lock);
 1069         enabled = prof_enabled;
 1070         prof_enabled = 0;
 1071         for (i = 0; i < SC_TABLESIZE; i++)
 1072                 LIST_INIT(&sleepq_hash[i]);
 1073         LIST_INIT(&sleepq_prof_free);
 1074         for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
 1075                 sp = &sleepq_profent[i];
 1076                 sp->sp_wmesg = NULL;
 1077                 sp->sp_count = 0;
 1078                 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
 1079         }
 1080         prof_enabled = enabled;
 1081         mtx_unlock_spin(&sleepq_prof_lock);
 1082 }
 1083 
 1084 static int
 1085 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
 1086 {
 1087         int error, v;
 1088 
 1089         v = prof_enabled;
 1090         error = sysctl_handle_int(oidp, &v, v, req);
 1091         if (error)
 1092                 return (error);
 1093         if (req->newptr == NULL)
 1094                 return (error);
 1095         if (v == prof_enabled)
 1096                 return (0);
 1097         if (v == 1)
 1098                 sleepq_prof_reset();
 1099         mtx_lock_spin(&sleepq_prof_lock);
 1100         prof_enabled = !!v;
 1101         mtx_unlock_spin(&sleepq_prof_lock);
 1102 
 1103         return (0);
 1104 }
 1105 
 1106 static int
 1107 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
 1108 {
 1109         int error, v;
 1110 
 1111         v = 0;
 1112         error = sysctl_handle_int(oidp, &v, 0, req);
 1113         if (error)
 1114                 return (error);
 1115         if (req->newptr == NULL)
 1116                 return (error);
 1117         if (v == 0)
 1118                 return (0);
 1119         sleepq_prof_reset();
 1120 
 1121         return (0);
 1122 }
 1123 
 1124 static int
 1125 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
 1126 {
 1127         struct sleepq_prof *sp;
 1128         struct sbuf *sb;
 1129         int enabled;
 1130         int error;
 1131         int i;
 1132 
 1133         error = sysctl_wire_old_buffer(req, 0);
 1134         if (error != 0)
 1135                 return (error);
 1136         sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req);
 1137         sbuf_printf(sb, "\nwmesg\tcount\n");
 1138         enabled = prof_enabled;
 1139         mtx_lock_spin(&sleepq_prof_lock);
 1140         prof_enabled = 0;
 1141         mtx_unlock_spin(&sleepq_prof_lock);
 1142         for (i = 0; i < SC_TABLESIZE; i++) {
 1143                 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
 1144                         sbuf_printf(sb, "%s\t%ld\n",
 1145                             sp->sp_wmesg, sp->sp_count);
 1146                 }
 1147         }
 1148         mtx_lock_spin(&sleepq_prof_lock);
 1149         prof_enabled = enabled;
 1150         mtx_unlock_spin(&sleepq_prof_lock);
 1151 
 1152         error = sbuf_finish(sb);
 1153         sbuf_delete(sb);
 1154         return (error);
 1155 }
 1156 
 1157 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
 1158     NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
 1159 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
 1160     NULL, 0, reset_sleepq_prof_stats, "I",
 1161     "Reset sleepqueue profiling statistics");
 1162 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
 1163     NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
 1164 #endif
 1165 
 1166 #ifdef DDB
 1167 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
 1168 {
 1169         struct sleepqueue_chain *sc;
 1170         struct sleepqueue *sq;
 1171 #ifdef INVARIANTS
 1172         struct lock_object *lock;
 1173 #endif
 1174         struct thread *td;
 1175         void *wchan;
 1176         int i;
 1177 
 1178         if (!have_addr)
 1179                 return;
 1180 
 1181         /*
 1182          * First, see if there is an active sleep queue for the wait channel
 1183          * indicated by the address.
 1184          */
 1185         wchan = (void *)addr;
 1186         sc = SC_LOOKUP(wchan);
 1187         LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
 1188                 if (sq->sq_wchan == wchan)
 1189                         goto found;
 1190 
 1191         /*
 1192          * Second, see if there is an active sleep queue at the address
 1193          * indicated.
 1194          */
 1195         for (i = 0; i < SC_TABLESIZE; i++)
 1196                 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
 1197                         if (sq == (struct sleepqueue *)addr)
 1198                                 goto found;
 1199                 }
 1200 
 1201         db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
 1202         return;
 1203 found:
 1204         db_printf("Wait channel: %p\n", sq->sq_wchan);
 1205         db_printf("Queue type: %d\n", sq->sq_type);
 1206 #ifdef INVARIANTS
 1207         if (sq->sq_lock) {
 1208                 lock = sq->sq_lock;
 1209                 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
 1210                     LOCK_CLASS(lock)->lc_name, lock->lo_name);
 1211         }
 1212 #endif
 1213         db_printf("Blocked threads:\n");
 1214         for (i = 0; i < NR_SLEEPQS; i++) {
 1215                 db_printf("\nQueue[%d]:\n", i);
 1216                 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
 1217                         db_printf("\tempty\n");
 1218                 else
 1219                         TAILQ_FOREACH(td, &sq->sq_blocked[0],
 1220                                       td_slpq) {
 1221                                 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
 1222                                           td->td_tid, td->td_proc->p_pid,
 1223                                           td->td_name);
 1224                         }
 1225                 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
 1226         }
 1227 }
 1228 
 1229 /* Alias 'show sleepqueue' to 'show sleepq'. */
 1230 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
 1231 #endif

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