pthread_cond_wait3
Wait on a condition variable
Usage
#include <pthread.h>
int
pthread_cond_wait(pthread_cond_t *restrict cond, pthread_mutex_t *restrict mutex);
Library
POSIX Threads Library (libpthread, -lpthread)
Overview
The pthread_cond_wait() function atomically blocks the current thread waiting on the condition variable specified by cond, and releases the mutex specified by mutex. The waiting thread unblocks after another thread calls pthread_cond_signal(3), or pthread_cond_broadcast(3) with the same condition variable, and the current thread reacquires the lock on mutex.
It is possible that the pthread_cond_wait() function returns without corresponding wakeup from either pthread_cond_signal() or pthread_cond_broadcast(). Such condition is called spurious wakeup, and is allowed by ISO/IEC 9945-1:1996 (“POSIX.1”). Applications should have a boolean expression used for each wait on the condition variable, and recheck it after return from the pthread_cond_wait() function.
Return values
If successful, the pthread_cond_wait() function will return zero. Otherwise an error number will be returned to indicate the error.
Errors
The pthread_cond_wait() function will fail if:
- [EINVAL]
-
The value specified by cond or the value specified by mutex is invalid.
- [EPERM]
-
The specified mutex was not locked by the calling thread.
- [EOWNERDEAD]
-
The argument mutex points to a robust mutex and the process containing the previous owning thread terminated while holding the mutex lock. The lock was granted to the caller and it is up to the new owner to make the state consistent.
- [ENOTRECOVERABLE]
-
The state protected by the mutex is not recoverable.
Releases
79 releases since FreeBSD 2.2.8-RELEASE; the text changed 43 times.