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fix some semaphore wait semantics (race condition deadlock and error checking)

This commit is contained in:
Rich Felker 2011-03-10 21:52:18 -05:00
parent 81af503610
commit cfe581b6bc
2 changed files with 7 additions and 1 deletions
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5
src/thread/sem_timedwait.c
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@ -8,7 +8,12 @@ int sem_timedwait(sem_t *sem, const struct timespec *at)
for (;;) { for (;;) {
if (a_fetch_add(sem->__val, -1) > 0) return 0; if (a_fetch_add(sem->__val, -1) > 0) return 0;
val = a_fetch_add(sem->__val, 1)+1; val = a_fetch_add(sem->__val, 1)+1;
if (val==1) __wake(sem->__val, 1, 0);
CANCELPT_BEGIN; CANCELPT_BEGIN;
if (at && at->tv_nsec >= 1000000000UL) {
errno = EINVAL;
return -1;
}
if (val <= 0 && __timedwait(sem->__val, val, CLOCK_REALTIME, at, 0) == ETIMEDOUT) { if (val <= 0 && __timedwait(sem->__val, val, CLOCK_REALTIME, at, 0) == ETIMEDOUT) {
errno = ETIMEDOUT; errno = ETIMEDOUT;
return -1; return -1;

3
src/thread/sem_trywait.c
View File

@ -5,7 +5,8 @@ int sem_trywait(sem_t *sem)
{ {
int val = a_fetch_add(sem->__val, -1); int val = a_fetch_add(sem->__val, -1);
if (val > 0) return 0; if (val > 0) return 0;
a_inc(sem->__val); if (!a_fetch_add(sem->__val, 1))
__wake(sem->__val, 1, 0);
errno = EAGAIN; errno = EAGAIN;
return -1; return -1;
} }