diff options
Diffstat (limited to 'linuxthreads')
| -rw-r--r-- | linuxthreads/ChangeLog | 6 | ||||
| -rw-r--r-- | linuxthreads/condvar.c | 88 |
2 files changed, 72 insertions, 22 deletions
diff --git a/linuxthreads/ChangeLog b/linuxthreads/ChangeLog index a151848cbf..c4247b290c 100644 --- a/linuxthreads/ChangeLog +++ b/linuxthreads/ChangeLog @@ -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. diff --git a/linuxthreads/condvar.c b/linuxthreads/condvar.c index a6a31ca715..ae1cef1ea9 100644 --- a/linuxthreads/condvar.c +++ b/linuxthreads/condvar.c @@ -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; - - /* __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); - - if (was_on_queue) { - __pthread_set_own_extricate_if(self, 0); - pthread_mutex_lock(mutex); - return ETIMEDOUT; + 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(&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; + } + + /* 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; } |