Don't grab the state lock to check for cancellation around condition
variables, as _lwp_wakeup/lwp_park provide the necessary barrier.
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@ -1,4 +1,4 @@
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$NetBSD: TODO,v 1.6 2007/02/15 15:39:33 yamt Exp $
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$NetBSD: TODO,v 1.7 2007/03/02 17:47:40 ad Exp $
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Bugs to fix, mostly with SA:
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@ -108,10 +108,6 @@ Future work for 1:1 threads:
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that does something similar. Again, lots of thought and benchmarking
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required. (Original idea from matt@)
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- It's possible that we don't need to take so many spinlocks around
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cancellation points like pthread_cond_wait() given that _lwp_wakeup()
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and _lwp_unpark() need to synchronise anyway.
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- Need to give consideration to the order in which threads enter and exit
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synchronisation objects, both in the pthread library and in the kernel.
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Commonly locks are acquired/released in order (a, b, c -> c, b, a). The
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@ -1,4 +1,4 @@
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/* $NetBSD: pthread_cond.c,v 1.20 2006/12/24 18:39:46 ad Exp $ */
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/* $NetBSD: pthread_cond.c,v 1.21 2007/03/02 17:47:40 ad Exp $ */
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/*-
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* Copyright (c) 2001 The NetBSD Foundation, Inc.
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@ -37,7 +37,7 @@
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: pthread_cond.c,v 1.20 2006/12/24 18:39:46 ad Exp $");
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__RCSID("$NetBSD: pthread_cond.c,v 1.21 2007/03/02 17:47:40 ad Exp $");
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#include <errno.h>
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#include <sys/time.h>
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@ -119,15 +119,11 @@ pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
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if (__predict_false(pthread__started == 0))
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return pthread_cond_wait_nothread(self, mutex, NULL);
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#ifdef PTHREAD_SA
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pthread_spinlock(self, &cond->ptc_lock);
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SDPRINTF(("(cond wait %p) Waiting on %p, mutex %p\n",
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self, cond, mutex));
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pthread_spinlock(self, &self->pt_statelock);
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if (__predict_false(self->pt_cancel)) {
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pthread_spinunlock(self, &self->pt_statelock);
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pthread_spinunlock(self, &cond->ptc_lock);
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pthread_exit(PTHREAD_CANCELED);
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}
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#ifdef ERRORCHECK
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if (cond->ptc_mutex == NULL)
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cond->ptc_mutex = mutex;
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@ -137,7 +133,13 @@ pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
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cond->ptc_mutex == mutex);
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#endif
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#ifdef PTHREAD_SA
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pthread_spinlock(self, &self->pt_statelock);
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if (__predict_false(self->pt_cancel)) {
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pthread_spinunlock(self, &self->pt_statelock);
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pthread_spinunlock(self, &cond->ptc_lock);
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pthread_exit(PTHREAD_CANCELED);
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}
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self->pt_sleepobj = cond;
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self->pt_state = PT_STATE_BLOCKED_QUEUE;
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self->pt_sleepq = &cond->ptc_waiters;
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@ -149,8 +151,20 @@ pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
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pthread__block(self, &cond->ptc_lock);
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/* Spinlock is unlocked on return */
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#else /* PTHREAD_SA */
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SDPRINTF(("(cond wait %p) Waiting on %p, mutex %p\n",
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self, cond, mutex));
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if (__predict_false(self->pt_cancel))
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pthread_exit(PTHREAD_CANCELED);
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pthread_spinlock(self, &cond->ptc_lock);
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#ifdef ERRORCHECK
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if (cond->ptc_mutex == NULL)
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cond->ptc_mutex = mutex;
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else
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pthread__error(EINVAL,
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"Multiple mutexes used for condition wait",
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cond->ptc_mutex == mutex);
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#endif
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pthread_mutex_unlock(mutex);
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pthread_spinunlock(self, &self->pt_statelock);
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(void)pthread__park(self, &cond->ptc_lock, cond,
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&cond->ptc_waiters, NULL, 0, 1);
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pthread_spinunlock(self, &cond->ptc_lock);
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@ -206,10 +220,12 @@ pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
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if (__predict_false(pthread__started == 0))
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return pthread_cond_wait_nothread(self, mutex, abstime);
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pthread_spinlock(self, &cond->ptc_lock);
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wait.ptw_thread = self;
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wait.ptw_cond = cond;
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retval = 0;
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#ifdef PTHREAD_SA
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pthread_spinlock(self, &cond->ptc_lock);
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SDPRINTF(("(cond timed wait %p) Waiting on %p until %d.%06ld\n",
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self, cond, abstime->tv_sec, abstime->tv_nsec/1000));
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@ -228,7 +244,6 @@ pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
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cond->ptc_mutex == mutex);
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#endif
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#ifdef PTHREAD_SA
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pthread__alarm_add(self, &alarm, abstime, pthread_cond_wait__callback,
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&wait);
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self->pt_state = PT_STATE_BLOCKED_QUEUE;
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@ -246,8 +261,21 @@ pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
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if (pthread__alarm_fired(&alarm))
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retval = ETIMEDOUT;
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#else /* PTHREAD_SA */
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SDPRINTF(("(cond timed wait %p) Waiting on %p until %d.%06ld\n",
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self, cond, abstime->tv_sec, abstime->tv_nsec/1000));
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if (__predict_false(self->pt_cancel))
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pthread_exit(PTHREAD_CANCELED);
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pthread_spinlock(self, &cond->ptc_lock);
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#ifdef ERRORCHECK
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if (cond->ptc_mutex == NULL)
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cond->ptc_mutex = mutex;
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else
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pthread__error(EINVAL,
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"Multiple mutexes used for condition wait",
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cond->ptc_mutex == mutex);
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#endif
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pthread_mutex_unlock(mutex);
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pthread_spinunlock(self, &self->pt_statelock);
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retval = pthread__park(self, &cond->ptc_lock, cond,
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&cond->ptc_waiters, abstime, 0, 1);
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pthread_spinunlock(self, &cond->ptc_lock);
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@ -328,18 +356,26 @@ pthread_cond_signal(pthread_cond_t *cond)
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pthread_spinunlock(self, &cond->ptc_lock);
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}
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#else /* PTHREAD_SA */
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self = pthread__self();
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pthread_spinlock(self, &cond->ptc_lock);
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if ((signaled = PTQ_FIRST(&cond->ptc_waiters)) != NULL) {
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PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
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PTHREADD_ADD(PTHREADD_COND_WOKEUP);
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if (!PTQ_EMPTY(&cond->ptc_waiters)) {
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self = pthread__self();
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pthread_spinlock(self, &cond->ptc_lock);
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signaled = PTQ_FIRST(&cond->ptc_waiters);
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if (signaled != NULL) {
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PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
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#ifdef ERRORCHECK
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if (PTQ_EMPTY(&cond->ptc_waiters))
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cond->ptc_mutex = NULL;
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#endif
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pthread__unpark(self, &cond->ptc_lock, cond, signaled);
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PTHREADD_ADD(PTHREADD_COND_WOKEUP);
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} else {
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#ifdef ERRORCHECK
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if (PTQ_EMPTY(&cond->ptc_waiters))
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cond->ptc_mutex = NULL;
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#endif
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pthread_spinunlock(self, &cond->ptc_lock);
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}
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}
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pthread__unpark(self, &cond->ptc_lock, cond, signaled);
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#endif /* PTHREAD_SA */
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#endif
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return 0;
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}
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@ -358,29 +394,23 @@ pthread_cond_broadcast(pthread_cond_t *cond)
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SDPRINTF(("(cond signal %p) Broadcasting %p\n",
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pthread__self(), cond));
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#ifdef PTHREAD_SA
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if (!PTQ_EMPTY(&cond->ptc_waiters)) {
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self = pthread__self();
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pthread_spinlock(self, &cond->ptc_lock);
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blockedq = cond->ptc_waiters;
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PTQ_INIT(&cond->ptc_waiters);
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#ifdef ERRORCHECK
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cond->ptc_mutex = NULL;
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#endif
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#ifdef PTHREAD_SA
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blockedq = cond->ptc_waiters;
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PTQ_INIT(&cond->ptc_waiters);
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pthread__sched_sleepers(self, &blockedq);
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PTHREADD_ADD(PTHREADD_COND_WOKEUP);
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pthread_spinunlock(self, &cond->ptc_lock);
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}
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#else /* PTHREAD_SA */
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self = pthread__self();
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pthread_spinlock(self, &cond->ptc_lock);
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#ifdef ERRORCHECK
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if (!PTQ_EMPTY(&cond->ptc_waiters))
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cond->ptc_mutex = NULL;
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#endif
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pthread__unpark_all(self, &cond->ptc_lock, cond, &cond->ptc_waiters);
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PTHREADD_ADD(PTHREADD_COND_WOKEUP);
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pthread__unpark_all(self, &cond->ptc_lock, cond, &cond->ptc_waiters);
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PTHREADD_ADD(PTHREADD_COND_WOKEUP);
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#endif /* PTHREAD_SA */
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}
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return 0;
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