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2000-07-24  Ulrich Drepper  <drepper@redhat.com>

	* condvar.c: Handle spurious wakeups.  [PR libc/1749].

	* spinlock.h: If IMPLEMENT_TAS_WITH_CAS is defined use
This commit is contained in:
Ulrich Drepper 2000-07-24 07:43:31 +00:00
parent 7603ea28d3
commit 5122880a26
2 changed files with 69 additions and 19 deletions
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6
linuxthreads/ChangeLog
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@ -1,6 +1,10 @@
2000-07-24 Ulrich Drepper <drepper@redhat.com>
* condvar.c: Handle spurious wakeups. [PR libc/1749].
2000-07-21 Ulrich Drepper <drepper@redhat.com>
* linuxthreads/spinlock.h: If IMPLEMENT_TAS_WITH_CAS is defined use
* spinlock.h: If IMPLEMENT_TAS_WITH_CAS is defined use
__compare_and_swap to define testandset.
* linuxthreads/sysdeps/powerpc/pt-machine.h: Add volatile to asms.
Define IMPLEMENT_TAS_WITH_CAS.

82
linuxthreads/condvar.c
View File

@ -60,6 +60,7 @@ int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
volatile pthread_descr self = thread_self();
pthread_extricate_if extr;
int already_canceled = 0;
int spurious_wakeup_count;
/* Check whether the mutex is locked and owned by this thread. */
if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP
@ -72,6 +73,7 @@ int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
extr.pu_extricate_func = cond_extricate_func;
/* Register extrication interface */
THREAD_SETMEM(self, p_condvar_avail, 0);
__pthread_set_own_extricate_if(self, &extr);
/* Atomically enqueue thread for waiting, but only if it is not
@ -96,7 +98,20 @@ int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
pthread_mutex_unlock(mutex);
suspend(self);
spurious_wakeup_count = 0;
while (1)
{
suspend(self);
if (THREAD_GETMEM(self, p_condvar_avail) == 0
&& THREAD_GETMEM(self, p_woken_by_cancel) == 0)
{
/* Count resumes that don't belong to us. */
spurious_wakeup_count++;
continue;
}
break;
}
__pthread_set_own_extricate_if(self, 0);
/* Check for cancellation again, to provide correct cancellation
@ -109,6 +124,10 @@ int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
pthread_exit(PTHREAD_CANCELED);
}
/* Put back any resumes we caught that don't belong to us. */
while (spurious_wakeup_count--)
restart(self);
pthread_mutex_lock(mutex);
return 0;
}
@ -121,6 +140,7 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
volatile pthread_descr self = thread_self();
int already_canceled = 0;
pthread_extricate_if extr;
int spurious_wakeup_count;
/* Check whether the mutex is locked and owned by this thread. */
if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP
@ -133,6 +153,7 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
extr.pu_extricate_func = cond_extricate_func;
/* Register extrication interface */
THREAD_SETMEM(self, p_condvar_avail, 0);
__pthread_set_own_extricate_if(self, &extr);
/* Enqueue to wait on the condition and check for cancellation. */
@ -151,26 +172,39 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
pthread_mutex_unlock(mutex);
if (!timedsuspend(self, abstime)) {
int was_on_queue;
spurious_wakeup_count = 0;
while (1)
{
if (!timedsuspend(self, abstime)) {
int was_on_queue;
/* __pthread_lock will queue back any spurious restarts that
may happen to it. */
/* __pthread_lock will queue back any spurious restarts that
may happen to it. */
__pthread_lock(&cond->__c_lock, self);
was_on_queue = remove_from_queue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
__pthread_lock(&cond->__c_lock, self);
was_on_queue = remove_from_queue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
if (was_on_queue) {
__pthread_set_own_extricate_if(self, 0);
pthread_mutex_lock(mutex);
return ETIMEDOUT;
if (was_on_queue) {
__pthread_set_own_extricate_if(self, 0);
pthread_mutex_lock(mutex);
return ETIMEDOUT;
}
/* Eat the outstanding restart() from the signaller */
suspend(self);
}
if (THREAD_GETMEM(self, p_condvar_avail) == 0
&& THREAD_GETMEM(self, p_woken_by_cancel) == 0)
{
/* Count resumes that don't belong to us. */
spurious_wakeup_count++;
continue;
}
break;
}
/* Eat the outstanding restart() from the signaller */
suspend(self);
}
__pthread_set_own_extricate_if(self, 0);
/* The remaining logic is the same as in other cancellable waits,
@ -183,6 +217,10 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
pthread_exit(PTHREAD_CANCELED);
}
/* Put back any resumes we caught that don't belong to us. */
while (spurious_wakeup_count--)
restart(self);
pthread_mutex_lock(mutex);
return 0;
}
@ -201,7 +239,11 @@ int pthread_cond_signal(pthread_cond_t *cond)
__pthread_lock(&cond->__c_lock, NULL);
th = dequeue(&cond->__c_waiting);
__pthread_unlock(&cond->__c_lock);
if (th != NULL) restart(th);
if (th != NULL) {
th->p_condvar_avail = 1;
WRITE_MEMORY_BARRIER();
restart(th);
}
return 0;
}
@ -215,7 +257,11 @@ int pthread_cond_broadcast(pthread_cond_t *cond)
cond->__c_waiting = NULL;
__pthread_unlock(&cond->__c_lock);
/* Now signal each process in the queue */
while ((th = dequeue(&tosignal)) != NULL) restart(th);
while ((th = dequeue(&tosignal)) != NULL) {
th->p_condvar_avail = 1;
WRITE_MEMORY_BARRIER();
restart(th);
}
return 0;
}