From cfe581b6bc795e3f00ac30791314ec0f9be4b4ad Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 10 Mar 2011 21:52:18 -0500 Subject: [PATCH] fix some semaphore wait semantics (race condition deadlock and error checking) --- src/thread/sem_timedwait.c | 5 +++++ src/thread/sem_trywait.c | 3 ++- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/src/thread/sem_timedwait.c b/src/thread/sem_timedwait.c index e6c2495a..ad3bf075 100644 --- a/src/thread/sem_timedwait.c +++ b/src/thread/sem_timedwait.c @@ -8,7 +8,12 @@ int sem_timedwait(sem_t *sem, const struct timespec *at) for (;;) { if (a_fetch_add(sem->__val, -1) > 0) return 0; val = a_fetch_add(sem->__val, 1)+1; + if (val==1) __wake(sem->__val, 1, 0); CANCELPT_BEGIN; + if (at && at->tv_nsec >= 1000000000UL) { + errno = EINVAL; + return -1; + } if (val <= 0 && __timedwait(sem->__val, val, CLOCK_REALTIME, at, 0) == ETIMEDOUT) { errno = ETIMEDOUT; return -1; diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c index d0e928ef..c5370c70 100644 --- a/src/thread/sem_trywait.c +++ b/src/thread/sem_trywait.c @@ -5,7 +5,8 @@ int sem_trywait(sem_t *sem) { int val = a_fetch_add(sem->__val, -1); if (val > 0) return 0; - a_inc(sem->__val); + if (!a_fetch_add(sem->__val, 1)) + __wake(sem->__val, 1, 0); errno = EAGAIN; return -1; } -- 2.25.1