kern_condvar.c

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    1 /*-
    2  * Copyright (c) 2000 Jake Burkholder <jake@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  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: releng/10.0/sys/kern/kern_condvar.c 255745 2013-09-20 23:06:21Z davide $");
   29 
   30 #include "opt_ktrace.h"
   31 
   32 #include <sys/param.h>
   33 #include <sys/systm.h>
   34 #include <sys/lock.h>
   35 #include <sys/mutex.h>
   36 #include <sys/proc.h>
   37 #include <sys/kernel.h>
   38 #include <sys/ktr.h>
   39 #include <sys/condvar.h>
   40 #include <sys/sched.h>
   41 #include <sys/signalvar.h>
   42 #include <sys/sleepqueue.h>
   43 #include <sys/resourcevar.h>
   44 #ifdef KTRACE
   45 #include <sys/uio.h>
   46 #include <sys/ktrace.h>
   47 #endif
   48 
   49 /*
   50  * Common sanity checks for cv_wait* functions.
   51  */
   52 #define CV_ASSERT(cvp, lock, td) do {                                   \
   53         KASSERT((td) != NULL, ("%s: td NULL", __func__));               \
   54         KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__));  \
   55         KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__));             \
   56         KASSERT((lock) != NULL, ("%s: lock NULL", __func__));           \
   57 } while (0)
   58 
   59 /*
   60  * Initialize a condition variable.  Must be called before use.
   61  */
   62 void
   63 cv_init(struct cv *cvp, const char *desc)
   64 {
   65 
   66         cvp->cv_description = desc;
   67         cvp->cv_waiters = 0;
   68 }
   69 
   70 /*
   71  * Destroy a condition variable.  The condition variable must be re-initialized
   72  * in order to be re-used.
   73  */
   74 void
   75 cv_destroy(struct cv *cvp)
   76 {
   77 #ifdef INVARIANTS
   78         struct sleepqueue *sq;
   79 
   80         sleepq_lock(cvp);
   81         sq = sleepq_lookup(cvp);
   82         sleepq_release(cvp);
   83         KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__));
   84 #endif
   85 }
   86 
   87 /*
   88  * Wait on a condition variable.  The current thread is placed on the condition
   89  * variable's wait queue and suspended.  A cv_signal or cv_broadcast on the same
   90  * condition variable will resume the thread.  The mutex is released before
   91  * sleeping and will be held on return.  It is recommended that the mutex be
   92  * held when cv_signal or cv_broadcast are called.
   93  */
   94 void
   95 _cv_wait(struct cv *cvp, struct lock_object *lock)
   96 {
   97         WITNESS_SAVE_DECL(lock_witness);
   98         struct lock_class *class;
   99         struct thread *td;
  100         uintptr_t lock_state;
  101 
  102         td = curthread;
  103         lock_state = 0;
  104 #ifdef KTRACE
  105         if (KTRPOINT(td, KTR_CSW))
  106                 ktrcsw(1, 0, cv_wmesg(cvp));
  107 #endif
  108         CV_ASSERT(cvp, lock, td);
  109         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  110             "Waiting on \"%s\"", cvp->cv_description);
  111         class = LOCK_CLASS(lock);
  112 
  113         if (cold || panicstr) {
  114                 /*
  115                  * During autoconfiguration, just give interrupts
  116                  * a chance, then just return.  Don't run any other
  117                  * thread or panic below, in case this is the idle
  118                  * process and already asleep.
  119                  */
  120                 return;
  121         }
  122 
  123         sleepq_lock(cvp);
  124 
  125         cvp->cv_waiters++;
  126         if (lock == &Giant.lock_object)
  127                 mtx_assert(&Giant, MA_OWNED);
  128         DROP_GIANT();
  129 
  130         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
  131         if (lock != &Giant.lock_object) {
  132                 if (class->lc_flags & LC_SLEEPABLE)
  133                         sleepq_release(cvp);
  134                 WITNESS_SAVE(lock, lock_witness);
  135                 lock_state = class->lc_unlock(lock);
  136                 if (class->lc_flags & LC_SLEEPABLE)
  137                         sleepq_lock(cvp);
  138         }
  139         sleepq_wait(cvp, 0);
  140 
  141 #ifdef KTRACE
  142         if (KTRPOINT(td, KTR_CSW))
  143                 ktrcsw(0, 0, cv_wmesg(cvp));
  144 #endif
  145         PICKUP_GIANT();
  146         if (lock != &Giant.lock_object) {
  147                 class->lc_lock(lock, lock_state);
  148                 WITNESS_RESTORE(lock, lock_witness);
  149         }
  150 }
  151 
  152 /*
  153  * Wait on a condition variable.  This function differs from cv_wait by
  154  * not aquiring the mutex after condition variable was signaled.
  155  */
  156 void
  157 _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
  158 {
  159         struct lock_class *class;
  160         struct thread *td;
  161 
  162         td = curthread;
  163 #ifdef KTRACE
  164         if (KTRPOINT(td, KTR_CSW))
  165                 ktrcsw(1, 0, cv_wmesg(cvp));
  166 #endif
  167         CV_ASSERT(cvp, lock, td);
  168         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  169             "Waiting on \"%s\"", cvp->cv_description);
  170         KASSERT(lock != &Giant.lock_object,
  171             ("cv_wait_unlock cannot be used with Giant"));
  172         class = LOCK_CLASS(lock);
  173 
  174         if (cold || panicstr) {
  175                 /*
  176                  * During autoconfiguration, just give interrupts
  177                  * a chance, then just return.  Don't run any other
  178                  * thread or panic below, in case this is the idle
  179                  * process and already asleep.
  180                  */
  181                 class->lc_unlock(lock);
  182                 return;
  183         }
  184 
  185         sleepq_lock(cvp);
  186 
  187         cvp->cv_waiters++;
  188         DROP_GIANT();
  189 
  190         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
  191         if (class->lc_flags & LC_SLEEPABLE)
  192                 sleepq_release(cvp);
  193         class->lc_unlock(lock);
  194         if (class->lc_flags & LC_SLEEPABLE)
  195                 sleepq_lock(cvp);
  196         sleepq_wait(cvp, 0);
  197 
  198 #ifdef KTRACE
  199         if (KTRPOINT(td, KTR_CSW))
  200                 ktrcsw(0, 0, cv_wmesg(cvp));
  201 #endif
  202         PICKUP_GIANT();
  203 }
  204 
  205 /*
  206  * Wait on a condition variable, allowing interruption by signals.  Return 0 if
  207  * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
  208  * a signal was caught.  If ERESTART is returned the system call should be
  209  * restarted if possible.
  210  */
  211 int
  212 _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
  213 {
  214         WITNESS_SAVE_DECL(lock_witness);
  215         struct lock_class *class;
  216         struct thread *td;
  217         uintptr_t lock_state;
  218         int rval;
  219 
  220         td = curthread;
  221         lock_state = 0;
  222 #ifdef KTRACE
  223         if (KTRPOINT(td, KTR_CSW))
  224                 ktrcsw(1, 0, cv_wmesg(cvp));
  225 #endif
  226         CV_ASSERT(cvp, lock, td);
  227         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  228             "Waiting on \"%s\"", cvp->cv_description);
  229         class = LOCK_CLASS(lock);
  230 
  231         if (cold || panicstr) {
  232                 /*
  233                  * After a panic, or during autoconfiguration, just give
  234                  * interrupts a chance, then just return; don't run any other
  235                  * procs or panic below, in case this is the idle process and
  236                  * already asleep.
  237                  */
  238                 return (0);
  239         }
  240 
  241         sleepq_lock(cvp);
  242 
  243         cvp->cv_waiters++;
  244         if (lock == &Giant.lock_object)
  245                 mtx_assert(&Giant, MA_OWNED);
  246         DROP_GIANT();
  247 
  248         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
  249             SLEEPQ_INTERRUPTIBLE, 0);
  250         if (lock != &Giant.lock_object) {
  251                 if (class->lc_flags & LC_SLEEPABLE)
  252                         sleepq_release(cvp);
  253                 WITNESS_SAVE(lock, lock_witness);
  254                 lock_state = class->lc_unlock(lock);
  255                 if (class->lc_flags & LC_SLEEPABLE)
  256                         sleepq_lock(cvp);
  257         }
  258         rval = sleepq_wait_sig(cvp, 0);
  259 
  260 #ifdef KTRACE
  261         if (KTRPOINT(td, KTR_CSW))
  262                 ktrcsw(0, 0, cv_wmesg(cvp));
  263 #endif
  264         PICKUP_GIANT();
  265         if (lock != &Giant.lock_object) {
  266                 class->lc_lock(lock, lock_state);
  267                 WITNESS_RESTORE(lock, lock_witness);
  268         }
  269 
  270         return (rval);
  271 }
  272 
  273 /*
  274  * Wait on a condition variable for (at most) the value specified in sbt
  275  * argument. Returns 0 if the process was resumed by cv_signal or cv_broadcast,
  276  * EWOULDBLOCK if the timeout expires.
  277  */
  278 int
  279 _cv_timedwait_sbt(struct cv *cvp, struct lock_object *lock, sbintime_t sbt,
  280     sbintime_t pr, int flags)
  281 {
  282         WITNESS_SAVE_DECL(lock_witness);
  283         struct lock_class *class;
  284         struct thread *td;
  285         int lock_state, rval;
  286 
  287         td = curthread;
  288         lock_state = 0;
  289 #ifdef KTRACE
  290         if (KTRPOINT(td, KTR_CSW))
  291                 ktrcsw(1, 0, cv_wmesg(cvp));
  292 #endif
  293         CV_ASSERT(cvp, lock, td);
  294         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  295             "Waiting on \"%s\"", cvp->cv_description);
  296         class = LOCK_CLASS(lock);
  297 
  298         if (cold || panicstr) {
  299                 /*
  300                  * After a panic, or during autoconfiguration, just give
  301                  * interrupts a chance, then just return; don't run any other
  302                  * thread or panic below, in case this is the idle process and
  303                  * already asleep.
  304                  */
  305                 return 0;
  306         }
  307 
  308         sleepq_lock(cvp);
  309 
  310         cvp->cv_waiters++;
  311         if (lock == &Giant.lock_object)
  312                 mtx_assert(&Giant, MA_OWNED);
  313         DROP_GIANT();
  314 
  315         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
  316         sleepq_set_timeout_sbt(cvp, sbt, pr, flags);
  317         if (lock != &Giant.lock_object) {
  318                 if (class->lc_flags & LC_SLEEPABLE)
  319                         sleepq_release(cvp);
  320                 WITNESS_SAVE(lock, lock_witness);
  321                 lock_state = class->lc_unlock(lock);
  322                 if (class->lc_flags & LC_SLEEPABLE)
  323                         sleepq_lock(cvp);
  324         }
  325         rval = sleepq_timedwait(cvp, 0);
  326 
  327 #ifdef KTRACE
  328         if (KTRPOINT(td, KTR_CSW))
  329                 ktrcsw(0, 0, cv_wmesg(cvp));
  330 #endif
  331         PICKUP_GIANT();
  332         if (lock != &Giant.lock_object) {
  333                 class->lc_lock(lock, lock_state);
  334                 WITNESS_RESTORE(lock, lock_witness);
  335         }
  336 
  337         return (rval);
  338 }
  339 
  340 /*
  341  * Wait on a condition variable for (at most) the value specified in sbt 
  342  * argument, allowing interruption by signals.
  343  * Returns 0 if the thread was resumed by cv_signal or cv_broadcast,
  344  * EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if a signal
  345  * was caught.
  346  */
  347 int
  348 _cv_timedwait_sig_sbt(struct cv *cvp, struct lock_object *lock,
  349     sbintime_t sbt, sbintime_t pr, int flags)
  350 {
  351         WITNESS_SAVE_DECL(lock_witness);
  352         struct lock_class *class;
  353         struct thread *td;
  354         int lock_state, rval;
  355 
  356         td = curthread;
  357         lock_state = 0;
  358 #ifdef KTRACE
  359         if (KTRPOINT(td, KTR_CSW))
  360                 ktrcsw(1, 0, cv_wmesg(cvp));
  361 #endif
  362         CV_ASSERT(cvp, lock, td);
  363         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  364             "Waiting on \"%s\"", cvp->cv_description);
  365         class = LOCK_CLASS(lock);
  366 
  367         if (cold || panicstr) {
  368                 /*
  369                  * After a panic, or during autoconfiguration, just give
  370                  * interrupts a chance, then just return; don't run any other
  371                  * thread or panic below, in case this is the idle process and
  372                  * already asleep.
  373                  */
  374                 return 0;
  375         }
  376 
  377         sleepq_lock(cvp);
  378 
  379         cvp->cv_waiters++;
  380         if (lock == &Giant.lock_object)
  381                 mtx_assert(&Giant, MA_OWNED);
  382         DROP_GIANT();
  383 
  384         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
  385             SLEEPQ_INTERRUPTIBLE, 0);
  386         sleepq_set_timeout_sbt(cvp, sbt, pr, flags);
  387         if (lock != &Giant.lock_object) {
  388                 if (class->lc_flags & LC_SLEEPABLE)
  389                         sleepq_release(cvp);
  390                 WITNESS_SAVE(lock, lock_witness);
  391                 lock_state = class->lc_unlock(lock);
  392                 if (class->lc_flags & LC_SLEEPABLE)
  393                         sleepq_lock(cvp);
  394         }
  395         rval = sleepq_timedwait_sig(cvp, 0);
  396 
  397 #ifdef KTRACE
  398         if (KTRPOINT(td, KTR_CSW))
  399                 ktrcsw(0, 0, cv_wmesg(cvp));
  400 #endif
  401         PICKUP_GIANT();
  402         if (lock != &Giant.lock_object) {
  403                 class->lc_lock(lock, lock_state);
  404                 WITNESS_RESTORE(lock, lock_witness);
  405         }
  406 
  407         return (rval);
  408 }
  409 
  410 /*
  411  * Signal a condition variable, wakes up one waiting thread.  Will also wakeup
  412  * the swapper if the process is not in memory, so that it can bring the
  413  * sleeping process in.  Note that this may also result in additional threads
  414  * being made runnable.  Should be called with the same mutex as was passed to
  415  * cv_wait held.
  416  */
  417 void
  418 cv_signal(struct cv *cvp)
  419 {
  420         int wakeup_swapper;
  421 
  422         wakeup_swapper = 0;
  423         sleepq_lock(cvp);
  424         if (cvp->cv_waiters > 0) {
  425                 cvp->cv_waiters--;
  426                 wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 0);
  427         }
  428         sleepq_release(cvp);
  429         if (wakeup_swapper)
  430                 kick_proc0();
  431 }
  432 
  433 /*
  434  * Broadcast a signal to a condition variable.  Wakes up all waiting threads.
  435  * Should be called with the same mutex as was passed to cv_wait held.
  436  */
  437 void
  438 cv_broadcastpri(struct cv *cvp, int pri)
  439 {
  440         int wakeup_swapper;
  441 
  442         /*
  443          * XXX sleepq_broadcast pri argument changed from -1 meaning
  444          * no pri to 0 meaning no pri.
  445          */
  446         wakeup_swapper = 0;
  447         if (pri == -1)
  448                 pri = 0;
  449         sleepq_lock(cvp);
  450         if (cvp->cv_waiters > 0) {
  451                 cvp->cv_waiters = 0;
  452                 wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0);
  453         }
  454         sleepq_release(cvp);
  455         if (wakeup_swapper)
  456                 kick_proc0();
  457 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_condvar.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_condvar.c
