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glibc/nptl/DESIGN-barrier.txt
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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; | |
} |