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2004-03-01 Ulrich Drepper <drepper@redhat.com> * sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S (__pthread_cond_timedwait): Optimize wakeup test. * sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S (__pthread_cond_wait): Likewise. * sysdeps/pthread/pthread_cond_wait.c (__pthread_cond_wait): Likewise. * sysdeps/pthread/pthread_cond_timedwait.c (__pthread_cond_timedwait): Likewise.
113 lines
1.7 KiB
Plaintext
113 lines
1.7 KiB
Plaintext
Conditional Variable pseudocode.
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int pthread_cond_timedwait (pthread_cond_t *cv, pthread_mutex_t *mutex);
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int pthread_cond_signal (pthread_cond_t *cv);
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int pthread_cond_broadcast (pthread_cond_t *cv);
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struct pthread_cond_t {
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unsigned int cond_lock;
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internal mutex
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uint64_t total_seq;
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Total number of threads using the conditional variable.
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uint64_t wakeup_seq;
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sequence number for next wakeup.
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uint64_t woken_seq;
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sequence number of last woken thread.
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}
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cleanup_handler(cv)
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{
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lll_lock(cv->lock);
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++cv->wakeup_seq;
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++cv->woken_seq;
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/* make sure no signal gets lost. */
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FUTEX_WAKE(cv->wakeup_seq, ALL);
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lll_unlock(cv->lock);
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}
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cond_timedwait(cv, mutex, timeout):
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{
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lll_lock(cv->lock);
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mutex_unlock(mutex);
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cleanup_push
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++cv->total_seq;
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val = seq = cv->wakeup_seq;
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while (1) {
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lll_unlock(cv->lock);
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enable_async
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ret = FUTEX_WAIT(cv->wakeup_seq, val, timeout);
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restore_async
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lll_lock(cv->lock);
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val = cv->wakeup_seq;
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if (val != seq && cv->woken_seq != val) {
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ret = 0;
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break;
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}
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if (ret == TIMEDOUT) {
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++cv->wakeup_seq;
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break;
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}
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}
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++cv->woken_seq;
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lll_unlock(cv->lock);
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cleanup_pop
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mutex_lock(mutex);
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return ret;
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}
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cond_signal(cv)
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{
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lll_lock(cv->lock);
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if (cv->total_seq > cv->wakeup_seq) {
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++cv->wakeup_seq;
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FUTEX_WAKE(cv->wakeup_seq, 1);
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}
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lll_unlock(cv->lock);
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}
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cond_broadcast(cv)
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{
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lll_lock(cv->lock);
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if (cv->total_seq > cv->wakeup_seq) {
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cv->wakeup_seq = cv->total_seq;
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FUTEX_WAKE(cv->wakeup_seq, ALL);
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}
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lll_unlock(cv->lock);
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}
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