diff options
Diffstat (limited to 'libc/bionic/semaphore.c')
| -rw-r--r-- | libc/bionic/semaphore.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/libc/bionic/semaphore.c b/libc/bionic/semaphore.c index fa9de0e..0c94600 100644 --- a/libc/bionic/semaphore.c +++ b/libc/bionic/semaphore.c @@ -29,6 +29,7 @@ #include <errno.h> #include <sys/time.h> #include <sys/atomics.h> +#include <time.h> int sem_init(sem_t *sem, int pshared, unsigned int value) { @@ -118,6 +119,62 @@ int sem_wait(sem_t *sem) return 0; } +int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout) +{ + int ret; + + if (sem == NULL) { + errno = EINVAL; + return -1; + } + + /* POSIX says we need to try to decrement the semaphore + * before checking the timeout value */ + if (__atomic_dec_if_positive(&sem->count)) + return 0; + + /* check it as per Posix */ + if (abs_timeout == NULL || + abs_timeout->tv_sec < 0 || + abs_timeout->tv_nsec < 0 || + abs_timeout->tv_nsec >= 1000000000) + { + errno = EINVAL; + return -1; + } + + for (;;) { + struct timespec ts; + int ret; + + /* Posix mandates CLOCK_REALTIME here */ + clock_gettime( CLOCK_REALTIME, &ts ); + ts.tv_sec = abs_timeout->tv_sec - ts.tv_sec; + ts.tv_nsec = abs_timeout->tv_nsec - ts.tv_nsec; + if (ts.tv_nsec < 0) { + ts.tv_nsec += 1000000000; + ts.tv_sec -= 1; + } + + if (ts.tv_sec < 0 || ts.tv_nsec < 0) { + errno = ETIMEDOUT; + return -1; + } + + ret = __futex_wait(&sem->count, 0, &ts); + + /* return in case of timeout or interrupt */ + if (ret == -ETIMEDOUT || ret == -EINTR) { + errno = -ret; + return -1; + } + + if (__atomic_dec_if_positive(&sem->count)) + break; + } + return 0; +} + int sem_post(sem_t *sem) { if (sem == NULL) |