135 lines
2.1 KiB
Plaintext
135 lines
2.1 KiB
Plaintext
Conditional Variable pseudocode.
|
|
================================
|
|
|
|
int pthread_cond_timedwait (pthread_cond_t *cv, pthread_mutex_t *mutex);
|
|
int pthread_cond_signal (pthread_cond_t *cv);
|
|
int pthread_cond_broadcast (pthread_cond_t *cv);
|
|
|
|
struct pthread_cond_t {
|
|
|
|
unsigned int cond_lock;
|
|
|
|
internal mutex
|
|
|
|
uint64_t total_seq;
|
|
|
|
Total number of threads using the conditional variable.
|
|
|
|
uint64_t wakeup_seq;
|
|
|
|
sequence number for next wakeup.
|
|
|
|
uint64_t woken_seq;
|
|
|
|
sequence number of last woken thread.
|
|
|
|
uint32_t broadcast_seq;
|
|
|
|
}
|
|
|
|
|
|
struct cv_data {
|
|
|
|
pthread_cond_t *cv;
|
|
|
|
uint32_t bc_seq
|
|
|
|
}
|
|
|
|
|
|
|
|
cleanup_handler(cv_data)
|
|
{
|
|
cv = cv_data->cv;
|
|
lll_lock(cv->lock);
|
|
|
|
if (cv_data->bc_seq == cv->broadcast_seq) {
|
|
++cv->wakeup_seq;
|
|
++cv->woken_seq;
|
|
}
|
|
|
|
/* make sure no signal gets lost. */
|
|
FUTEX_WAKE(cv->wakeup_seq, ALL);
|
|
|
|
lll_unlock(cv->lock);
|
|
}
|
|
|
|
|
|
cond_timedwait(cv, mutex, timeout):
|
|
{
|
|
lll_lock(cv->lock);
|
|
mutex_unlock(mutex);
|
|
|
|
cleanup_push
|
|
|
|
++cv->total_seq;
|
|
val = seq = cv->wakeup_seq;
|
|
cv_data.bc = cv->broadcast_seq;
|
|
cv_data.cv = cv;
|
|
|
|
while (1) {
|
|
|
|
lll_unlock(cv->lock);
|
|
|
|
enable_async(&cv_data);
|
|
|
|
ret = FUTEX_WAIT(cv->wakeup_seq, val, timeout);
|
|
|
|
restore_async
|
|
|
|
lll_lock(cv->lock);
|
|
|
|
if (bc != cv->broadcast_seq)
|
|
goto bc_out;
|
|
|
|
val = cv->wakeup_seq;
|
|
|
|
if (val != seq && cv->woken_seq != val) {
|
|
ret = 0;
|
|
break;
|
|
}
|
|
|
|
if (ret == TIMEDOUT) {
|
|
++cv->wakeup_seq;
|
|
break;
|
|
}
|
|
}
|
|
|
|
++cv->woken_seq;
|
|
|
|
bc_out:
|
|
lll_unlock(cv->lock);
|
|
|
|
cleanup_pop
|
|
|
|
mutex_lock(mutex);
|
|
|
|
return ret;
|
|
}
|
|
|
|
cond_signal(cv)
|
|
{
|
|
lll_lock(cv->lock);
|
|
|
|
if (cv->total_seq > cv->wakeup_seq) {
|
|
++cv->wakeup_seq;
|
|
FUTEX_WAKE(cv->wakeup_seq, 1);
|
|
}
|
|
|
|
lll_unlock(cv->lock);
|
|
}
|
|
|
|
cond_broadcast(cv)
|
|
{
|
|
lll_lock(cv->lock);
|
|
|
|
if (cv->total_seq > cv->wakeup_seq) {
|
|
cv->wakeup_seq = cv->total_seq;
|
|
cv->woken_seq = cv->total_seq;
|
|
++cv->broadcast_seq;
|
|
FUTEX_WAKE(cv->wakeup_seq, ALL);
|
|
}
|
|
|
|
lll_unlock(cv->lock);
|
|
}
|