45 lines
938 B
Plaintext
45 lines
938 B
Plaintext
Barriers pseudocode
|
|
===================
|
|
|
|
int pthread_barrier_wait(barrier_t *barrier);
|
|
|
|
struct barrier_t {
|
|
|
|
unsigned int lock:
|
|
- internal mutex
|
|
|
|
unsigned int left;
|
|
- current barrier count, # of threads still needed.
|
|
|
|
unsigned int init_count;
|
|
- number of threads needed for the barrier to continue.
|
|
|
|
unsigned int curr_event;
|
|
- generation count
|
|
}
|
|
|
|
pthread_barrier_wait(barrier_t *barrier)
|
|
{
|
|
unsigned int event;
|
|
result = 0;
|
|
|
|
lll_lock(barrier->lock);
|
|
if (!--barrier->left) {
|
|
barrier->curr_event++;
|
|
futex_wake(&barrier->curr_event, INT_MAX)
|
|
|
|
result = BARRIER_SERIAL_THREAD;
|
|
} else {
|
|
event = barrier->curr_event;
|
|
lll_unlock(barrier->lock);
|
|
do {
|
|
futex_wait(&barrier->curr_event, event)
|
|
} while (event == barrier->curr_event);
|
|
}
|
|
|
|
if (atomic_increment_val (barrier->left) == barrier->init_count)
|
|
lll_unlock(barrier->lock);
|
|
|
|
return result;
|
|
}
|