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change sem_trywait algorithm so it never has to call __wake

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This commit is contained in:
Rich Felker 2011-04-14 15:10:50 -04:00
commit e983aea0ae
1 changed files with 2 additions and 3 deletions
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5
src/thread/sem_trywait.c
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@ -3,9 +3,8 @@
int sem_trywait(sem_t *sem) int sem_trywait(sem_t *sem)
{ {
if (a_fetch_add(sem->__val, -1) > 0) return 0; int val = sem->__val[0];
if (!a_fetch_add(sem->__val, 1) && sem->__val[1]) if (val>0 && a_cas(sem->__val, val, val-1)==val) return 0;
__wake(sem->__val, 1, 0);
errno = EAGAIN; errno = EAGAIN;
return -1; return -1;
} }