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("$FreeBSD$");
   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: curthread 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         int lock_state;
  101 
  102         td = curthread;
  103 #ifdef KTRACE
  104         if (KTRPOINT(td, KTR_CSW))
  105                 ktrcsw(1, 0);
  106 #endif
  107         CV_ASSERT(cvp, lock, td);
  108         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  109             "Waiting on \"%s\"", cvp->cv_description);
  110         WITNESS_SAVE(lock, lock_witness);
  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         DROP_GIANT();
  127 
  128         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
  129         if (class->lc_flags & LC_SLEEPABLE)
  130                 sleepq_release(cvp);
  131         lock_state = class->lc_unlock(lock);
  132         if (class->lc_flags & LC_SLEEPABLE)
  133                 sleepq_lock(cvp);
  134         sleepq_wait(cvp);
  135 
  136 #ifdef KTRACE
  137         if (KTRPOINT(td, KTR_CSW))
  138                 ktrcsw(0, 0);
  139 #endif
  140         PICKUP_GIANT();
  141         class->lc_lock(lock, lock_state);
  142         WITNESS_RESTORE(lock, lock_witness);
  143 }
  144 
  145 /*
  146  * Wait on a condition variable.  This function differs from cv_wait by
  147  * not aquiring the mutex after condition variable was signaled.
  148  */
  149 void
  150 _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
  151 {
  152         struct lock_class *class;
  153         struct thread *td;
  154 
  155         td = curthread;
  156 #ifdef KTRACE
  157         if (KTRPOINT(td, KTR_CSW))
  158                 ktrcsw(1, 0);
  159 #endif
  160         CV_ASSERT(cvp, lock, td);
  161         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  162             "Waiting on \"%s\"", cvp->cv_description);
  163         class = LOCK_CLASS(lock);
  164 
  165         if (cold || panicstr) {
  166                 /*
  167                  * During autoconfiguration, just give interrupts
  168                  * a chance, then just return.  Don't run any other
  169                  * thread or panic below, in case this is the idle
  170                  * process and already asleep.
  171                  */
  172                 class->lc_unlock(lock);
  173                 return;
  174         }
  175 
  176         sleepq_lock(cvp);
  177 
  178         cvp->cv_waiters++;
  179         DROP_GIANT();
  180 
  181         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
  182         if (class->lc_flags & LC_SLEEPABLE)
  183                 sleepq_release(cvp);
  184         class->lc_unlock(lock);
  185         if (class->lc_flags & LC_SLEEPABLE)
  186                 sleepq_lock(cvp);
  187         sleepq_wait(cvp);
  188 
  189 #ifdef KTRACE
  190         if (KTRPOINT(td, KTR_CSW))
  191                 ktrcsw(0, 0);
  192 #endif
  193         PICKUP_GIANT();
  194 }
  195 
  196 /*
  197  * Wait on a condition variable, allowing interruption by signals.  Return 0 if
  198  * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
  199  * a signal was caught.  If ERESTART is returned the system call should be
  200  * restarted if possible.
  201  */
  202 int
  203 _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
  204 {
  205         WITNESS_SAVE_DECL(lock_witness);
  206         struct lock_class *class;
  207         struct thread *td;
  208         struct proc *p;
  209         int lock_state, rval;
  210 
  211         td = curthread;
  212         p = td->td_proc;
  213 #ifdef KTRACE
  214         if (KTRPOINT(td, KTR_CSW))
  215                 ktrcsw(1, 0);
  216 #endif
  217         CV_ASSERT(cvp, lock, td);
  218         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  219             "Waiting on \"%s\"", cvp->cv_description);
  220         WITNESS_SAVE(lock, lock_witness);
  221         class = LOCK_CLASS(lock);
  222 
  223         if (cold || panicstr) {
  224                 /*
  225                  * After a panic, or during autoconfiguration, just give
  226                  * interrupts a chance, then just return; don't run any other
  227                  * procs or panic below, in case this is the idle process and
  228                  * already asleep.
  229                  */
  230                 return (0);
  231         }
  232 
  233         sleepq_lock(cvp);
  234 
  235         cvp->cv_waiters++;
  236         DROP_GIANT();
  237 
  238         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
  239             SLEEPQ_INTERRUPTIBLE, 0);
  240         if (class->lc_flags & LC_SLEEPABLE)
  241                 sleepq_release(cvp);
  242         lock_state = class->lc_unlock(lock);
  243         if (class->lc_flags & LC_SLEEPABLE)
  244                 sleepq_lock(cvp);
  245         rval = sleepq_wait_sig(cvp);
  246 
  247 #ifdef KTRACE
  248         if (KTRPOINT(td, KTR_CSW))
  249                 ktrcsw(0, 0);
  250 #endif
  251         PICKUP_GIANT();
  252         class->lc_lock(lock, lock_state);
  253         WITNESS_RESTORE(lock, lock_witness);
  254 
  255         return (rval);
  256 }
  257 
  258 /*
  259  * Wait on a condition variable for at most timo/hz seconds.  Returns 0 if the
  260  * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout
  261  * expires.
  262  */
  263 int
  264 _cv_timedwait(struct cv *cvp, struct lock_object *lock, int timo)
  265 {
  266         WITNESS_SAVE_DECL(lock_witness);
  267         struct lock_class *class;
  268         struct thread *td;
  269         int lock_state, rval;
  270 
  271         td = curthread;
  272         rval = 0;
  273 #ifdef KTRACE
  274         if (KTRPOINT(td, KTR_CSW))
  275                 ktrcsw(1, 0);
  276 #endif
  277         CV_ASSERT(cvp, lock, td);
  278         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  279             "Waiting on \"%s\"", cvp->cv_description);
  280         WITNESS_SAVE(lock, lock_witness);
  281         class = LOCK_CLASS(lock);
  282 
  283         if (cold || panicstr) {
  284                 /*
  285                  * After a panic, or during autoconfiguration, just give
  286                  * interrupts a chance, then just return; don't run any other
  287                  * thread or panic below, in case this is the idle process and
  288                  * already asleep.
  289                  */
  290                 return 0;
  291         }
  292 
  293         sleepq_lock(cvp);
  294 
  295         cvp->cv_waiters++;
  296         DROP_GIANT();
  297 
  298         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
  299         sleepq_set_timeout(cvp, timo);
  300         if (class->lc_flags & LC_SLEEPABLE)
  301                 sleepq_release(cvp);
  302         lock_state = class->lc_unlock(lock);
  303         if (class->lc_flags & LC_SLEEPABLE)
  304                 sleepq_lock(cvp);
  305         rval = sleepq_timedwait(cvp);
  306 
  307 #ifdef KTRACE
  308         if (KTRPOINT(td, KTR_CSW))
  309                 ktrcsw(0, 0);
  310 #endif
  311         PICKUP_GIANT();
  312         class->lc_lock(lock, lock_state);
  313         WITNESS_RESTORE(lock, lock_witness);
  314 
  315         return (rval);
  316 }
  317 
  318 /*
  319  * Wait on a condition variable for at most timo/hz seconds, allowing
  320  * interruption by signals.  Returns 0 if the thread was resumed by cv_signal
  321  * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if
  322  * a signal was caught.
  323  */
  324 int
  325 _cv_timedwait_sig(struct cv *cvp, struct lock_object *lock, int timo)
  326 {
  327         WITNESS_SAVE_DECL(lock_witness);
  328         struct lock_class *class;
  329         struct thread *td;
  330         struct proc *p;
  331         int lock_state, rval;
  332 
  333         td = curthread;
  334         p = td->td_proc;
  335         rval = 0;
  336 #ifdef KTRACE
  337         if (KTRPOINT(td, KTR_CSW))
  338                 ktrcsw(1, 0);
  339 #endif
  340         CV_ASSERT(cvp, lock, td);
  341         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  342             "Waiting on \"%s\"", cvp->cv_description);
  343         WITNESS_SAVE(lock, lock_witness);
  344         class = LOCK_CLASS(lock);
  345 
  346         if (cold || panicstr) {
  347                 /*
  348                  * After a panic, or during autoconfiguration, just give
  349                  * interrupts a chance, then just return; don't run any other
  350                  * thread or panic below, in case this is the idle process and
  351                  * already asleep.
  352                  */
  353                 return 0;
  354         }
  355 
  356         sleepq_lock(cvp);
  357 
  358         cvp->cv_waiters++;
  359         DROP_GIANT();
  360 
  361         sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
  362             SLEEPQ_INTERRUPTIBLE, 0);
  363         sleepq_set_timeout(cvp, timo);
  364         if (class->lc_flags & LC_SLEEPABLE)
  365                 sleepq_release(cvp);
  366         lock_state = class->lc_unlock(lock);
  367         if (class->lc_flags & LC_SLEEPABLE)
  368                 sleepq_lock(cvp);
  369         rval = sleepq_timedwait_sig(cvp);
  370 
  371 #ifdef KTRACE
  372         if (KTRPOINT(td, KTR_CSW))
  373                 ktrcsw(0, 0);
  374 #endif
  375         PICKUP_GIANT();
  376         class->lc_lock(lock, lock_state);
  377         WITNESS_RESTORE(lock, lock_witness);
  378 
  379         return (rval);
  380 }
  381 
  382 /*
  383  * Signal a condition variable, wakes up one waiting thread.  Will also wakeup
  384  * the swapper if the process is not in memory, so that it can bring the
  385  * sleeping process in.  Note that this may also result in additional threads
  386  * being made runnable.  Should be called with the same mutex as was passed to
  387  * cv_wait held.
  388  */
  389 void
  390 cv_signal(struct cv *cvp)
  391 {
  392 
  393         sleepq_lock(cvp);
  394         if (cvp->cv_waiters > 0) {
  395                 cvp->cv_waiters--;
  396                 sleepq_signal(cvp, SLEEPQ_CONDVAR, -1, 0);
  397         }
  398         sleepq_release(cvp);
  399 }
  400 
  401 /*
  402  * Broadcast a signal to a condition variable.  Wakes up all waiting threads.
  403  * Should be called with the same mutex as was passed to cv_wait held.
  404  */
  405 void
  406 cv_broadcastpri(struct cv *cvp, int pri)
  407 {
  408 
  409         sleepq_lock(cvp);
  410         if (cvp->cv_waiters > 0) {
  411                 cvp->cv_waiters = 0;
  412                 sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0);
  413         } else
  414                 sleepq_release(cvp);
  415 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_condvar.c

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