45 lines
948 B
Plaintext
45 lines
948 B
Plaintext
Barriers pseudocode
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===================
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int pthread_barrier_wait(barrier_t *barrier);
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struct barrier_t {
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unsigned int lock:
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- internal mutex
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unsigned int left;
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- current barrier count, # of threads still needed.
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unsigned int init_count;
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- number of threads needed for the barrier to continue.
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unsigned int curr_event;
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- generation count
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}
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pthread_barrier_wait(barrier_t *barrier)
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{
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unsigned int event;
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result = 0;
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lll_lock(barrier->lock);
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if (!--barrier->left) {
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barrier->curr_event++;
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futex_wake(&barrier->curr_event, INT_MAX)
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result = BARRIER_SERIAL_THREAD;
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} else {
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event = barrier->curr_event;
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lll_unlock(barrier->lock);
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do {
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futex_wait(&barrier->curr_event, event)
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} while (event == barrier->curr_event);
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}
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if (atomic_exchange_and_add (barrier->left, 1) == barrier->init_count - 1)
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lll_unlock(barrier->lock);
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return result;
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}
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