| #include "pthread_impl.h" |
| |
| static void undo(void *control) |
| { |
| a_store(control, 0); |
| __wake(control, 1, 1); |
| } |
| |
| int __pthread_once(pthread_once_t *control, void (*init)(void)) |
| { |
| static int waiters; |
| |
| /* Return immediately if init finished before */ |
| if (*control == 2) return 0; |
| |
| /* Try to enter initializing state. Three possibilities: |
| * 0 - we're the first or the other cancelled; run init |
| * 1 - another thread is running init; wait |
| * 2 - another thread finished running init; just return */ |
| |
| for (;;) switch (a_cas(control, 0, 1)) { |
| case 0: |
| pthread_cleanup_push(undo, control); |
| init(); |
| pthread_cleanup_pop(0); |
| |
| a_store(control, 2); |
| if (waiters) __wake(control, -1, 1); |
| return 0; |
| case 1: |
| __wait(control, &waiters, 1, 1); |
| continue; |
| case 2: |
| return 0; |
| } |
| } |
| |
| weak_alias(__pthread_once, pthread_once); |