The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: 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/8.4/sys/kern/subr_sleepqueue.c 236345 2012-05-30 23:42:48Z rstone $");
   64 
   65 #include "opt_sleepqueue_profiling.h"
   66 #include "opt_ddb.h"
   67 #include "opt_kdtrace.h"
   68 #include "opt_sched.h"
   69 
   70 #include <sys/param.h>
   71 #include <sys/systm.h>
   72 #include <sys/lock.h>
   73 #include <sys/kernel.h>
   74 #include <sys/ktr.h>
   75 #include <sys/mutex.h>
   76 #include <sys/proc.h>
   77 #include <sys/sbuf.h>
   78 #include <sys/sched.h>
   79 #include <sys/sdt.h>
   80 #include <sys/signalvar.h>
   81 #include <sys/sleepqueue.h>
   82 #include <sys/sysctl.h>
   83 
   84 #include <vm/uma.h>
   85 
   86 #ifdef DDB
   87 #include <ddb/ddb.h>
   88 #endif
   89 
   90 /*
   91  * Constants for the hash table of sleep queue chains.  These constants are
   92  * the same ones that 4BSD (and possibly earlier versions of BSD) used.
   93  * Basically, we ignore the lower 8 bits of the address since most wait
   94  * channel pointers are aligned and only look at the next 7 bits for the
   95  * hash.  SC_TABLESIZE must be a power of two for SC_MASK to work properly.
   96  */
   97 #define SC_TABLESIZE    128                     /* Must be power of 2. */
   98 #define SC_MASK         (SC_TABLESIZE - 1)
   99 #define SC_SHIFT        8
  100 #define SC_HASH(wc)     (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
  101 #define SC_LOOKUP(wc)   &sleepq_chains[SC_HASH(wc)]
  102 #define NR_SLEEPQS      2
  103 /*
  104  * There two different lists of sleep queues.  Both lists are connected
  105  * via the sq_hash entries.  The first list is the sleep queue chain list
  106  * that a sleep queue is on when it is attached to a wait channel.  The
  107  * second list is the free list hung off of a sleep queue that is attached
  108  * to a wait channel.
  109  *
  110  * Each sleep queue also contains the wait channel it is attached to, the
  111  * list of threads blocked on that wait channel, flags specific to the
  112  * wait channel, and the lock used to synchronize with a wait channel.
  113  * The flags are used to catch mismatches between the various consumers
  114  * of the sleep queue API (e.g. sleep/wakeup and condition variables).
  115  * The lock pointer is only used when invariants are enabled for various
  116  * debugging checks.
  117  *
  118  * Locking key:
  119  *  c - sleep queue chain lock
  120  */
  121 struct sleepqueue {
  122         TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS];    /* (c) Blocked threads. */
  123         u_int sq_blockedcnt[NR_SLEEPQS];        /* (c) N. of blocked threads. */
  124         LIST_ENTRY(sleepqueue) sq_hash;         /* (c) Chain and free list. */
  125         LIST_HEAD(, sleepqueue) sq_free;        /* (c) Free queues. */
  126         void    *sq_wchan;                      /* (c) Wait channel. */
  127         int     sq_type;                        /* (c) Queue type. */
  128 #ifdef INVARIANTS
  129         struct lock_object *sq_lock;            /* (c) Associated lock. */
  130 #endif
  131 };
  132 
  133 struct sleepqueue_chain {
  134         LIST_HEAD(, sleepqueue) sc_queues;      /* List of sleep queues. */
  135         struct mtx sc_lock;                     /* Spin lock for this chain. */
  136 #ifdef SLEEPQUEUE_PROFILING
  137         u_int   sc_depth;                       /* Length of sc_queues. */
  138         u_int   sc_max_depth;                   /* Max length of sc_queues. */
  139 #endif
  140 };
  141 
  142 #ifdef SLEEPQUEUE_PROFILING
  143 u_int sleepq_max_depth;
  144 SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
  145 SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
  146     "sleepq chain stats");
  147 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
  148     0, "maxmimum depth achieved of a single chain");
  149 
  150 static void     sleepq_profile(const char *wmesg);
  151 static int      prof_enabled;
  152 #endif
  153 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
  154 static uma_zone_t sleepq_zone;
  155 
  156 /*
  157  * Prototypes for non-exported routines.
  158  */
  159 static int      sleepq_catch_signals(void *wchan, int pri);
  160 static int      sleepq_check_signals(void);
  161 static int      sleepq_check_timeout(void);
  162 #ifdef INVARIANTS
  163 static void     sleepq_dtor(void *mem, int size, void *arg);
  164 #endif
  165 static int      sleepq_init(void *mem, int size, int flags);
  166 static int      sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
  167                     int pri);
  168 static void     sleepq_switch(void *wchan, int pri);
  169 static void     sleepq_timeout(void *arg);
  170 
  171 SDT_PROBE_DECLARE(sched, , , sleep);
  172 SDT_PROBE_DECLARE(sched, , , wakeup);
  173 
  174 /*
  175  * Early initialization of sleep queues that is called from the sleepinit()
  176  * SYSINIT.
  177  */
  178 void
  179 init_sleepqueues(void)
  180 {
  181 #ifdef SLEEPQUEUE_PROFILING
  182         struct sysctl_oid *chain_oid;
  183         char chain_name[10];
  184 #endif
  185         int i;
  186 
  187         for (i = 0; i < SC_TABLESIZE; i++) {
  188                 LIST_INIT(&sleepq_chains[i].sc_queues);
  189                 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
  190                     MTX_SPIN | MTX_RECURSE);
  191 #ifdef SLEEPQUEUE_PROFILING
  192                 snprintf(chain_name, sizeof(chain_name), "%d", i);
  193                 chain_oid = SYSCTL_ADD_NODE(NULL, 
  194                     SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
  195                     chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
  196                 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
  197                     "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
  198                 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
  199                     "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
  200                     NULL);
  201 #endif
  202         }
  203         sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
  204 #ifdef INVARIANTS
  205             NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
  206 #else
  207             NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
  208 #endif
  209         
  210         thread0.td_sleepqueue = sleepq_alloc();
  211 }
  212 
  213 /*
  214  * Get a sleep queue for a new thread.
  215  */
  216 struct sleepqueue *
  217 sleepq_alloc(void)
  218 {
  219 
  220         return (uma_zalloc(sleepq_zone, M_WAITOK));
  221 }
  222 
  223 /*
  224  * Free a sleep queue when a thread is destroyed.
  225  */
  226 void
  227 sleepq_free(struct sleepqueue *sq)
  228 {
  229 
  230         uma_zfree(sleepq_zone, sq);
  231 }
  232 
  233 /*
  234  * Lock the sleep queue chain associated with the specified wait channel.
  235  */
  236 void
  237 sleepq_lock(void *wchan)
  238 {
  239         struct sleepqueue_chain *sc;
  240 
  241         sc = SC_LOOKUP(wchan);
  242         mtx_lock_spin(&sc->sc_lock);
  243 }
  244 
  245 /*
  246  * Look up the sleep queue associated with a given wait channel in the hash
  247  * table locking the associated sleep queue chain.  If no queue is found in
  248  * the table, NULL is returned.
  249  */
  250 struct sleepqueue *
  251 sleepq_lookup(void *wchan)
  252 {
  253         struct sleepqueue_chain *sc;
  254         struct sleepqueue *sq;
  255 
  256         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  257         sc = SC_LOOKUP(wchan);
  258         mtx_assert(&sc->sc_lock, MA_OWNED);
  259         LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
  260                 if (sq->sq_wchan == wchan)
  261                         return (sq);
  262         return (NULL);
  263 }
  264 
  265 /*
  266  * Unlock the sleep queue chain associated with a given wait channel.
  267  */
  268 void
  269 sleepq_release(void *wchan)
  270 {
  271         struct sleepqueue_chain *sc;
  272 
  273         sc = SC_LOOKUP(wchan);
  274         mtx_unlock_spin(&sc->sc_lock);
  275 }
  276 
  277 /*
  278  * Places the current thread on the sleep queue for the specified wait
  279  * channel.  If INVARIANTS is enabled, then it associates the passed in
  280  * lock with the sleepq to make sure it is held when that sleep queue is
  281  * woken up.
  282  */
  283 void
  284 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
  285     int queue)
  286 {
  287         struct sleepqueue_chain *sc;
  288         struct sleepqueue *sq;
  289         struct thread *td;
  290 
  291         td = curthread;
  292         sc = SC_LOOKUP(wchan);
  293         mtx_assert(&sc->sc_lock, MA_OWNED);
  294         MPASS(td->td_sleepqueue != NULL);
  295         MPASS(wchan != NULL);
  296         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  297 
  298         /* If this thread is not allowed to sleep, die a horrible death. */
  299         KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
  300             ("Trying sleep, but thread marked as sleeping prohibited"));
  301 
  302         /* Look up the sleep queue associated with the wait channel 'wchan'. */
  303         sq = sleepq_lookup(wchan);
  304 
  305         /*
  306          * If the wait channel does not already have a sleep queue, use
  307          * this thread's sleep queue.  Otherwise, insert the current thread
  308          * into the sleep queue already in use by this wait channel.
  309          */
  310         if (sq == NULL) {
  311 #ifdef INVARIANTS
  312                 int i;
  313 
  314                 sq = td->td_sleepqueue;
  315                 for (i = 0; i < NR_SLEEPQS; i++) {
  316                         KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
  317                             ("thread's sleep queue %d is not empty", i));
  318                         KASSERT(sq->sq_blockedcnt[i] == 0,
  319                             ("thread's sleep queue %d count mismatches", i));
  320                 }
  321                 KASSERT(LIST_EMPTY(&sq->sq_free),
  322                     ("thread's sleep queue has a non-empty free list"));
  323                 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
  324                 sq->sq_lock = lock;
  325 #endif
  326 #ifdef SLEEPQUEUE_PROFILING
  327                 sc->sc_depth++;
  328                 if (sc->sc_depth > sc->sc_max_depth) {
  329                         sc->sc_max_depth = sc->sc_depth;
  330                         if (sc->sc_max_depth > sleepq_max_depth)
  331                                 sleepq_max_depth = sc->sc_max_depth;
  332                 }
  333 #endif
  334                 sq = td->td_sleepqueue;
  335                 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
  336                 sq->sq_wchan = wchan;
  337                 sq->sq_type = flags & SLEEPQ_TYPE;
  338         } else {
  339                 MPASS(wchan == sq->sq_wchan);
  340                 MPASS(lock == sq->sq_lock);
  341                 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
  342                 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
  343         }
  344         thread_lock(td);
  345         TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
  346         sq->sq_blockedcnt[queue]++;
  347         td->td_sleepqueue = NULL;
  348         td->td_sqqueue = queue;
  349         td->td_wchan = wchan;
  350         td->td_wmesg = wmesg;
  351         if (flags & SLEEPQ_INTERRUPTIBLE) {
  352                 td->td_flags |= TDF_SINTR;
  353                 td->td_flags &= ~TDF_SLEEPABORT;
  354                 if (flags & SLEEPQ_STOP_ON_BDRY)
  355                         td->td_flags |= TDF_SBDRY;
  356         }
  357         thread_unlock(td);
  358 }
  359 
  360 /*
  361  * Sets a timeout that will remove the current thread from the specified
  362  * sleep queue after timo ticks if the thread has not already been awakened.
  363  */
  364 void
  365 sleepq_set_timeout(void *wchan, int timo)
  366 {
  367         struct sleepqueue_chain *sc;
  368         struct thread *td;
  369 
  370         td = curthread;
  371         sc = SC_LOOKUP(wchan);
  372         mtx_assert(&sc->sc_lock, MA_OWNED);
  373         MPASS(TD_ON_SLEEPQ(td));
  374         MPASS(td->td_sleepqueue == NULL);
  375         MPASS(wchan != NULL);
  376         callout_reset_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td);
  377 }
  378 
  379 /*
  380  * Return the number of actual sleepers for the specified queue.
  381  */
  382 u_int
  383 sleepq_sleepcnt(void *wchan, int queue)
  384 {
  385         struct sleepqueue *sq;
  386 
  387         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  388         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  389         sq = sleepq_lookup(wchan);
  390         if (sq == NULL)
  391                 return (0);
  392         return (sq->sq_blockedcnt[queue]);
  393 }
  394 
  395 /*
  396  * Marks the pending sleep of the current thread as interruptible and
  397  * makes an initial check for pending signals before putting a thread
  398  * to sleep. Enters and exits with the thread lock held.  Thread lock
  399  * may have transitioned from the sleepq lock to a run lock.
  400  */
  401 static int
  402 sleepq_catch_signals(void *wchan, int pri)
  403 {
  404         struct sleepqueue_chain *sc;
  405         struct sleepqueue *sq;
  406         struct thread *td;
  407         struct proc *p;
  408         struct sigacts *ps;
  409         int sig, ret, stop_allowed;
  410 
  411         td = curthread;
  412         p = curproc;
  413         sc = SC_LOOKUP(wchan);
  414         mtx_assert(&sc->sc_lock, MA_OWNED);
  415         MPASS(wchan != NULL);
  416         /*
  417          * See if there are any pending signals for this thread.  If not
  418          * we can switch immediately.  Otherwise do the signal processing
  419          * directly.
  420          */
  421         thread_lock(td);
  422         if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
  423                 sleepq_switch(wchan, pri);
  424                 return (0);
  425         }
  426         stop_allowed = (td->td_flags & TDF_SBDRY) ? SIG_STOP_NOT_ALLOWED :
  427             SIG_STOP_ALLOWED;
  428         thread_unlock(td);
  429         mtx_unlock_spin(&sc->sc_lock);
  430         CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
  431                 (void *)td, (long)p->p_pid, td->td_name);
  432         PROC_LOCK(p);
  433         ps = p->p_sigacts;
  434         mtx_lock(&ps->ps_mtx);
  435         sig = cursig(td, stop_allowed);
  436         if (sig == 0) {
  437                 mtx_unlock(&ps->ps_mtx);
  438                 ret = thread_suspend_check(1);
  439                 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
  440         } else {
  441                 if (SIGISMEMBER(ps->ps_sigintr, sig))
  442                         ret = EINTR;
  443                 else
  444                         ret = ERESTART;
  445                 mtx_unlock(&ps->ps_mtx);
  446         }
  447         /*
  448          * Lock the per-process spinlock prior to dropping the PROC_LOCK
  449          * to avoid a signal delivery race.  PROC_LOCK, PROC_SLOCK, and
  450          * thread_lock() are currently held in tdsignal().
  451          */
  452         PROC_SLOCK(p);
  453         mtx_lock_spin(&sc->sc_lock);
  454         PROC_UNLOCK(p);
  455         thread_lock(td);
  456         PROC_SUNLOCK(p);
  457         if (ret == 0) {
  458                 sleepq_switch(wchan, pri);
  459                 return (0);
  460         }
  461         /*
  462          * There were pending signals and this thread is still
  463          * on the sleep queue, remove it from the sleep queue.
  464          */
  465         if (TD_ON_SLEEPQ(td)) {
  466                 sq = sleepq_lookup(wchan);
  467                 if (sleepq_resume_thread(sq, td, 0)) {
  468 #ifdef INVARIANTS
  469                         /*
  470                          * This thread hasn't gone to sleep yet, so it
  471                          * should not be swapped out.
  472                          */
  473                         panic("not waking up swapper");
  474 #endif
  475                 }
  476         }
  477         mtx_unlock_spin(&sc->sc_lock);
  478         MPASS(td->td_lock != &sc->sc_lock);
  479         return (ret);
  480 }
  481 
  482 /*
  483  * Switches to another thread if we are still asleep on a sleep queue.
  484  * Returns with thread lock.
  485  */
  486 static void
  487 sleepq_switch(void *wchan, int pri)
  488 {
  489         struct sleepqueue_chain *sc;
  490         struct sleepqueue *sq;
  491         struct thread *td;
  492 
  493         td = curthread;
  494         sc = SC_LOOKUP(wchan);
  495         mtx_assert(&sc->sc_lock, MA_OWNED);
  496         THREAD_LOCK_ASSERT(td, MA_OWNED);
  497 
  498         /* 
  499          * If we have a sleep queue, then we've already been woken up, so
  500          * just return.
  501          */
  502         if (td->td_sleepqueue != NULL) {
  503                 mtx_unlock_spin(&sc->sc_lock);
  504                 return;
  505         }
  506 
  507         /*
  508          * If TDF_TIMEOUT is set, then our sleep has been timed out
  509          * already but we are still on the sleep queue, so dequeue the
  510          * thread and return.
  511          */
  512         if (td->td_flags & TDF_TIMEOUT) {
  513                 MPASS(TD_ON_SLEEPQ(td));
  514                 sq = sleepq_lookup(wchan);
  515                 if (sleepq_resume_thread(sq, td, 0)) {
  516 #ifdef INVARIANTS
  517                         /*
  518                          * This thread hasn't gone to sleep yet, so it
  519                          * should not be swapped out.
  520                          */
  521                         panic("not waking up swapper");
  522 #endif
  523                 }
  524                 mtx_unlock_spin(&sc->sc_lock);
  525                 return;         
  526         }
  527 #ifdef SLEEPQUEUE_PROFILING
  528         if (prof_enabled)
  529                 sleepq_profile(td->td_wmesg);
  530 #endif
  531         MPASS(td->td_sleepqueue == NULL);
  532         sched_sleep(td, pri);
  533         thread_lock_set(td, &sc->sc_lock);
  534         SDT_PROBE0(sched, , , sleep);
  535         TD_SET_SLEEPING(td);
  536         mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
  537         KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
  538         CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
  539             (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
  540 }
  541 
  542 /*
  543  * Check to see if we timed out.
  544  */
  545 static int
  546 sleepq_check_timeout(void)
  547 {
  548         struct thread *td;
  549 
  550         td = curthread;
  551         THREAD_LOCK_ASSERT(td, MA_OWNED);
  552 
  553         /*
  554          * If TDF_TIMEOUT is set, we timed out.
  555          */
  556         if (td->td_flags & TDF_TIMEOUT) {
  557                 td->td_flags &= ~TDF_TIMEOUT;
  558                 return (EWOULDBLOCK);
  559         }
  560 
  561         /*
  562          * If TDF_TIMOFAIL is set, the timeout ran after we had
  563          * already been woken up.
  564          */
  565         if (td->td_flags & TDF_TIMOFAIL)
  566                 td->td_flags &= ~TDF_TIMOFAIL;
  567 
  568         /*
  569          * If callout_stop() fails, then the timeout is running on
  570          * another CPU, so synchronize with it to avoid having it
  571          * accidentally wake up a subsequent sleep.
  572          */
  573         else if (callout_stop(&td->td_slpcallout) == 0) {
  574                 td->td_flags |= TDF_TIMEOUT;
  575                 TD_SET_SLEEPING(td);
  576                 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
  577         }
  578         return (0);
  579 }
  580 
  581 /*
  582  * Check to see if we were awoken by a signal.
  583  */
  584 static int
  585 sleepq_check_signals(void)
  586 {
  587         struct thread *td;
  588 
  589         td = curthread;
  590         THREAD_LOCK_ASSERT(td, MA_OWNED);
  591 
  592         /* We are no longer in an interruptible sleep. */
  593         if (td->td_flags & TDF_SINTR)
  594                 td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
  595 
  596         if (td->td_flags & TDF_SLEEPABORT) {
  597                 td->td_flags &= ~TDF_SLEEPABORT;
  598                 return (td->td_intrval);
  599         }
  600 
  601         return (0);
  602 }
  603 
  604 /*
  605  * Block the current thread until it is awakened from its sleep queue.
  606  */
  607 void
  608 sleepq_wait(void *wchan, int pri)
  609 {
  610         struct thread *td;
  611 
  612         td = curthread;
  613         MPASS(!(td->td_flags & TDF_SINTR));
  614         thread_lock(td);
  615         sleepq_switch(wchan, pri);
  616         thread_unlock(td);
  617 }
  618 
  619 /*
  620  * Block the current thread until it is awakened from its sleep queue
  621  * or it is interrupted by a signal.
  622  */
  623 int
  624 sleepq_wait_sig(void *wchan, int pri)
  625 {
  626         int rcatch;
  627         int rval;
  628 
  629         rcatch = sleepq_catch_signals(wchan, pri);
  630         rval = sleepq_check_signals();
  631         thread_unlock(curthread);
  632         if (rcatch)
  633                 return (rcatch);
  634         return (rval);
  635 }
  636 
  637 /*
  638  * Block the current thread until it is awakened from its sleep queue
  639  * or it times out while waiting.
  640  */
  641 int
  642 sleepq_timedwait(void *wchan, int pri)
  643 {
  644         struct thread *td;
  645         int rval;
  646 
  647         td = curthread;
  648         MPASS(!(td->td_flags & TDF_SINTR));
  649         thread_lock(td);
  650         sleepq_switch(wchan, pri);
  651         rval = sleepq_check_timeout();
  652         thread_unlock(td);
  653 
  654         return (rval);
  655 }
  656 
  657 /*
  658  * Block the current thread until it is awakened from its sleep queue,
  659  * it is interrupted by a signal, or it times out waiting to be awakened.
  660  */
  661 int
  662 sleepq_timedwait_sig(void *wchan, int pri)
  663 {
  664         int rcatch, rvalt, rvals;
  665 
  666         rcatch = sleepq_catch_signals(wchan, pri);
  667         rvalt = sleepq_check_timeout();
  668         rvals = sleepq_check_signals();
  669         thread_unlock(curthread);
  670         if (rcatch)
  671                 return (rcatch);
  672         if (rvals)
  673                 return (rvals);
  674         return (rvalt);
  675 }
  676 
  677 /*
  678  * Returns the type of sleepqueue given a waitchannel.
  679  */
  680 int
  681 sleepq_type(void *wchan)
  682 {
  683         struct sleepqueue *sq;
  684         int type;
  685 
  686         MPASS(wchan != NULL);
  687 
  688         sleepq_lock(wchan);
  689         sq = sleepq_lookup(wchan);
  690         if (sq == NULL) {
  691                 sleepq_release(wchan);
  692                 return (-1);
  693         }
  694         type = sq->sq_type;
  695         sleepq_release(wchan);
  696         return (type);
  697 }
  698 
  699 /*
  700  * Removes a thread from a sleep queue and makes it
  701  * runnable.
  702  */
  703 static int
  704 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
  705 {
  706         struct sleepqueue_chain *sc;
  707 
  708         MPASS(td != NULL);
  709         MPASS(sq->sq_wchan != NULL);
  710         MPASS(td->td_wchan == sq->sq_wchan);
  711         MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
  712         THREAD_LOCK_ASSERT(td, MA_OWNED);
  713         sc = SC_LOOKUP(sq->sq_wchan);
  714         mtx_assert(&sc->sc_lock, MA_OWNED);
  715 
  716         SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
  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                 sched_prio(td, pri);
  750 
  751         /*
  752          * Note that thread td might not be sleeping if it is running
  753          * sleepq_catch_signals() on another CPU or is blocked on its
  754          * proc lock to check signals.  There's no need to mark the
  755          * thread runnable in that case.
  756          */
  757         if (TD_IS_SLEEPING(td)) {
  758                 TD_CLR_SLEEPING(td);
  759                 return (setrunnable(td));
  760         }
  761         return (0);
  762 }
  763 
  764 #ifdef INVARIANTS
  765 /*
  766  * UMA zone item deallocator.
  767  */
  768 static void
  769 sleepq_dtor(void *mem, int size, void *arg)
  770 {
  771         struct sleepqueue *sq;
  772         int i;
  773 
  774         sq = mem;
  775         for (i = 0; i < NR_SLEEPQS; i++) {
  776                 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
  777                 MPASS(sq->sq_blockedcnt[i] == 0);
  778         }
  779 }
  780 #endif
  781 
  782 /*
  783  * UMA zone item initializer.
  784  */
  785 static int
  786 sleepq_init(void *mem, int size, int flags)
  787 {
  788         struct sleepqueue *sq;
  789         int i;
  790 
  791         bzero(mem, size);
  792         sq = mem;
  793         for (i = 0; i < NR_SLEEPQS; i++) {
  794                 TAILQ_INIT(&sq->sq_blocked[i]);
  795                 sq->sq_blockedcnt[i] = 0;
  796         }
  797         LIST_INIT(&sq->sq_free);
  798         return (0);
  799 }
  800 
  801 /*
  802  * Find the highest priority thread sleeping on a wait channel and resume it.
  803  */
  804 int
  805 sleepq_signal(void *wchan, int flags, int pri, int queue)
  806 {
  807         struct sleepqueue *sq;
  808         struct thread *td, *besttd;
  809         int wakeup_swapper;
  810 
  811         CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
  812         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  813         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  814         sq = sleepq_lookup(wchan);
  815         if (sq == NULL)
  816                 return (0);
  817         KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
  818             ("%s: mismatch between sleep/wakeup and cv_*", __func__));
  819 
  820         /*
  821          * Find the highest priority thread on the queue.  If there is a
  822          * tie, use the thread that first appears in the queue as it has
  823          * been sleeping the longest since threads are always added to
  824          * the tail of sleep queues.
  825          */
  826         besttd = NULL;
  827         TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
  828                 if (besttd == NULL || td->td_priority < besttd->td_priority)
  829                         besttd = td;
  830         }
  831         MPASS(besttd != NULL);
  832         thread_lock(besttd);
  833         wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
  834         thread_unlock(besttd);
  835         return (wakeup_swapper);
  836 }
  837 
  838 /*
  839  * Resume all threads sleeping on a specified wait channel.
  840  */
  841 int
  842 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
  843 {
  844         struct sleepqueue *sq;
  845         struct thread *td, *tdn;
  846         int wakeup_swapper;
  847 
  848         CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
  849         KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
  850         MPASS((queue >= 0) && (queue < NR_SLEEPQS));
  851         sq = sleepq_lookup(wchan);
  852         if (sq == NULL)
  853                 return (0);
  854         KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
  855             ("%s: mismatch between sleep/wakeup and cv_*", __func__));
  856 
  857         /* Resume all blocked threads on the sleep queue. */
  858         wakeup_swapper = 0;
  859         TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
  860                 thread_lock(td);
  861                 if (sleepq_resume_thread(sq, td, pri))
  862                         wakeup_swapper = 1;
  863                 thread_unlock(td);
  864         }
  865         return (wakeup_swapper);
  866 }
  867 
  868 /*
  869  * Time sleeping threads out.  When the timeout expires, the thread is
  870  * removed from the sleep queue and made runnable if it is still asleep.
  871  */
  872 static void
  873 sleepq_timeout(void *arg)
  874 {
  875         struct sleepqueue_chain *sc;
  876         struct sleepqueue *sq;
  877         struct thread *td;
  878         void *wchan;
  879         int wakeup_swapper;
  880 
  881         td = arg;
  882         wakeup_swapper = 0;
  883         CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
  884             (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
  885 
  886         /*
  887          * First, see if the thread is asleep and get the wait channel if
  888          * it is.
  889          */
  890         thread_lock(td);
  891         if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
  892                 wchan = td->td_wchan;
  893                 sc = SC_LOOKUP(wchan);
  894                 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
  895                 sq = sleepq_lookup(wchan);
  896                 MPASS(sq != NULL);
  897                 td->td_flags |= TDF_TIMEOUT;
  898                 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
  899                 thread_unlock(td);
  900                 if (wakeup_swapper)
  901                         kick_proc0();
  902                 return;
  903         }
  904 
  905         /*
  906          * If the thread is on the SLEEPQ but isn't sleeping yet, it
  907          * can either be on another CPU in between sleepq_add() and
  908          * one of the sleepq_*wait*() routines or it can be in
  909          * sleepq_catch_signals().
  910          */
  911         if (TD_ON_SLEEPQ(td)) {
  912                 td->td_flags |= TDF_TIMEOUT;
  913                 thread_unlock(td);
  914                 return;
  915         }
  916 
  917         /*
  918          * Now check for the edge cases.  First, if TDF_TIMEOUT is set,
  919          * then the other thread has already yielded to us, so clear
  920          * the flag and resume it.  If TDF_TIMEOUT is not set, then the
  921          * we know that the other thread is not on a sleep queue, but it
  922          * hasn't resumed execution yet.  In that case, set TDF_TIMOFAIL
  923          * to let it know that the timeout has already run and doesn't
  924          * need to be canceled.
  925          */
  926         if (td->td_flags & TDF_TIMEOUT) {
  927                 MPASS(TD_IS_SLEEPING(td));
  928                 td->td_flags &= ~TDF_TIMEOUT;
  929                 TD_CLR_SLEEPING(td);
  930                 wakeup_swapper = setrunnable(td);
  931         } else
  932                 td->td_flags |= TDF_TIMOFAIL;
  933         thread_unlock(td);
  934         if (wakeup_swapper)
  935                 kick_proc0();
  936 }
  937 
  938 /*
  939  * Resumes a specific thread from the sleep queue associated with a specific
  940  * wait channel if it is on that queue.
  941  */
  942 void
  943 sleepq_remove(struct thread *td, void *wchan)
  944 {
  945         struct sleepqueue *sq;
  946         int wakeup_swapper;
  947 
  948         /*
  949          * Look up the sleep queue for this wait channel, then re-check
  950          * that the thread is asleep on that channel, if it is not, then
  951          * bail.
  952          */
  953         MPASS(wchan != NULL);
  954         sleepq_lock(wchan);
  955         sq = sleepq_lookup(wchan);
  956         /*
  957          * We can not lock the thread here as it may be sleeping on a
  958          * different sleepq.  However, holding the sleepq lock for this
  959          * wchan can guarantee that we do not miss a wakeup for this
  960          * channel.  The asserts below will catch any false positives.
  961          */
  962         if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
  963                 sleepq_release(wchan);
  964                 return;
  965         }
  966         /* Thread is asleep on sleep queue sq, so wake it up. */
  967         thread_lock(td);
  968         MPASS(sq != NULL);
  969         MPASS(td->td_wchan == wchan);
  970         wakeup_swapper = sleepq_resume_thread(sq, td, 0);
  971         thread_unlock(td);
  972         sleepq_release(wchan);
  973         if (wakeup_swapper)
  974                 kick_proc0();
  975 }
  976 
  977 /*
  978  * Abort a thread as if an interrupt had occurred.  Only abort
  979  * interruptible waits (unfortunately it isn't safe to abort others).
  980  */
  981 int
  982 sleepq_abort(struct thread *td, int intrval)
  983 {
  984         struct sleepqueue *sq;
  985         void *wchan;
  986 
  987         THREAD_LOCK_ASSERT(td, MA_OWNED);
  988         MPASS(TD_ON_SLEEPQ(td));
  989         MPASS(td->td_flags & TDF_SINTR);
  990         MPASS(intrval == EINTR || intrval == ERESTART);
  991 
  992         /*
  993          * If the TDF_TIMEOUT flag is set, just leave. A
  994          * timeout is scheduled anyhow.
  995          */
  996         if (td->td_flags & TDF_TIMEOUT)
  997                 return (0);
  998 
  999         CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
 1000             (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
 1001         td->td_intrval = intrval;
 1002         td->td_flags |= TDF_SLEEPABORT;
 1003         /*
 1004          * If the thread has not slept yet it will find the signal in
 1005          * sleepq_catch_signals() and call sleepq_resume_thread.  Otherwise
 1006          * we have to do it here.
 1007          */
 1008         if (!TD_IS_SLEEPING(td))
 1009                 return (0);
 1010         wchan = td->td_wchan;
 1011         MPASS(wchan != NULL);
 1012         sq = sleepq_lookup(wchan);
 1013         MPASS(sq != NULL);
 1014 
 1015         /* Thread is asleep on sleep queue sq, so wake it up. */
 1016         return (sleepq_resume_thread(sq, td, 0));
 1017 }
 1018 
 1019 #ifdef SLEEPQUEUE_PROFILING
 1020 #define SLEEPQ_PROF_LOCATIONS   1024
 1021 #define SLEEPQ_SBUFSIZE         (40 * 512)
 1022 struct sleepq_prof {
 1023         LIST_ENTRY(sleepq_prof) sp_link;
 1024         const char      *sp_wmesg;
 1025         long            sp_count;
 1026 };
 1027 
 1028 LIST_HEAD(sqphead, sleepq_prof);
 1029 
 1030 struct sqphead sleepq_prof_free;
 1031 struct sqphead sleepq_hash[SC_TABLESIZE];
 1032 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
 1033 static struct mtx sleepq_prof_lock;
 1034 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
 1035 
 1036 static void
 1037 sleepq_profile(const char *wmesg)
 1038 {
 1039         struct sleepq_prof *sp;
 1040 
 1041         mtx_lock_spin(&sleepq_prof_lock);
 1042         if (prof_enabled == 0)
 1043                 goto unlock;
 1044         LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
 1045                 if (sp->sp_wmesg == wmesg)
 1046                         goto done;
 1047         sp = LIST_FIRST(&sleepq_prof_free);
 1048         if (sp == NULL)
 1049                 goto unlock;
 1050         sp->sp_wmesg = wmesg;
 1051         LIST_REMOVE(sp, sp_link);
 1052         LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
 1053 done:
 1054         sp->sp_count++;
 1055 unlock:
 1056         mtx_unlock_spin(&sleepq_prof_lock);
 1057         return;
 1058 }
 1059 
 1060 static void
 1061 sleepq_prof_reset(void)
 1062 {
 1063         struct sleepq_prof *sp;
 1064         int enabled;
 1065         int i;
 1066 
 1067         mtx_lock_spin(&sleepq_prof_lock);
 1068         enabled = prof_enabled;
 1069         prof_enabled = 0;
 1070         for (i = 0; i < SC_TABLESIZE; i++)
 1071                 LIST_INIT(&sleepq_hash[i]);
 1072         LIST_INIT(&sleepq_prof_free);
 1073         for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
 1074                 sp = &sleepq_profent[i];
 1075                 sp->sp_wmesg = NULL;
 1076                 sp->sp_count = 0;
 1077                 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
 1078         }
 1079         prof_enabled = enabled;
 1080         mtx_unlock_spin(&sleepq_prof_lock);
 1081 }
 1082 
 1083 static int
 1084 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
 1085 {
 1086         int error, v;
 1087 
 1088         v = prof_enabled;
 1089         error = sysctl_handle_int(oidp, &v, v, req);
 1090         if (error)
 1091                 return (error);
 1092         if (req->newptr == NULL)
 1093                 return (error);
 1094         if (v == prof_enabled)
 1095                 return (0);
 1096         if (v == 1)
 1097                 sleepq_prof_reset();
 1098         mtx_lock_spin(&sleepq_prof_lock);
 1099         prof_enabled = !!v;
 1100         mtx_unlock_spin(&sleepq_prof_lock);
 1101 
 1102         return (0);
 1103 }
 1104 
 1105 static int
 1106 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
 1107 {
 1108         int error, v;
 1109 
 1110         v = 0;
 1111         error = sysctl_handle_int(oidp, &v, 0, req);
 1112         if (error)
 1113                 return (error);
 1114         if (req->newptr == NULL)
 1115                 return (error);
 1116         if (v == 0)
 1117                 return (0);
 1118         sleepq_prof_reset();
 1119 
 1120         return (0);
 1121 }
 1122 
 1123 static int
 1124 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
 1125 {
 1126         static int multiplier = 1;
 1127         struct sleepq_prof *sp;
 1128         struct sbuf *sb;
 1129         int enabled;
 1130         int error;
 1131         int i;
 1132 
 1133 retry_sbufops:
 1134         sb = sbuf_new(NULL, NULL, SLEEPQ_SBUFSIZE * multiplier, SBUF_FIXEDLEN);
 1135         sbuf_printf(sb, "\nwmesg\tcount\n");
 1136         enabled = prof_enabled;
 1137         mtx_lock_spin(&sleepq_prof_lock);
 1138         prof_enabled = 0;
 1139         mtx_unlock_spin(&sleepq_prof_lock);
 1140         for (i = 0; i < SC_TABLESIZE; i++) {
 1141                 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
 1142                         sbuf_printf(sb, "%s\t%ld\n",
 1143                             sp->sp_wmesg, sp->sp_count);
 1144                         if (sbuf_overflowed(sb)) {
 1145                                 sbuf_delete(sb);
 1146                                 multiplier++;
 1147                                 goto retry_sbufops;
 1148                         }
 1149                 }
 1150         }
 1151         mtx_lock_spin(&sleepq_prof_lock);
 1152         prof_enabled = enabled;
 1153         mtx_unlock_spin(&sleepq_prof_lock);
 1154 
 1155         sbuf_finish(sb);
 1156         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 1157         sbuf_delete(sb);
 1158         return (error);
 1159 }
 1160 
 1161 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
 1162     NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
 1163 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
 1164     NULL, 0, reset_sleepq_prof_stats, "I",
 1165     "Reset sleepqueue profiling statistics");
 1166 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
 1167     NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
 1168 #endif
 1169 
 1170 #ifdef DDB
 1171 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
 1172 {
 1173         struct sleepqueue_chain *sc;
 1174         struct sleepqueue *sq;
 1175 #ifdef INVARIANTS
 1176         struct lock_object *lock;
 1177 #endif
 1178         struct thread *td;
 1179         void *wchan;
 1180         int i;
 1181 
 1182         if (!have_addr)
 1183                 return;
 1184 
 1185         /*
 1186          * First, see if there is an active sleep queue for the wait channel
 1187          * indicated by the address.
 1188          */
 1189         wchan = (void *)addr;
 1190         sc = SC_LOOKUP(wchan);
 1191         LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
 1192                 if (sq->sq_wchan == wchan)
 1193                         goto found;
 1194 
 1195         /*
 1196          * Second, see if there is an active sleep queue at the address
 1197          * indicated.
 1198          */
 1199         for (i = 0; i < SC_TABLESIZE; i++)
 1200                 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
 1201                         if (sq == (struct sleepqueue *)addr)
 1202                                 goto found;
 1203                 }
 1204 
 1205         db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
 1206         return;
 1207 found:
 1208         db_printf("Wait channel: %p\n", sq->sq_wchan);
 1209         db_printf("Queue type: %d\n", sq->sq_type);
 1210 #ifdef INVARIANTS
 1211         if (sq->sq_lock) {
 1212                 lock = sq->sq_lock;
 1213                 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
 1214                     LOCK_CLASS(lock)->lc_name, lock->lo_name);
 1215         }
 1216 #endif
 1217         db_printf("Blocked threads:\n");
 1218         for (i = 0; i < NR_SLEEPQS; i++) {
 1219                 db_printf("\nQueue[%d]:\n", i);
 1220                 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
 1221                         db_printf("\tempty\n");
 1222                 else
 1223                         TAILQ_FOREACH(td, &sq->sq_blocked[0],
 1224                                       td_slpq) {
 1225                                 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
 1226                                           td->td_tid, td->td_proc->p_pid,
 1227                                           td->td_name);
 1228                         }
 1229                 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
 1230         }
 1231 }
 1232 
 1233 /* Alias 'show sleepqueue' to 'show sleepq'. */
 1234 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
 1235 #endif

Cache object: a415012df72e1be581e9f3ef4e853450


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