Multithreaded Programming Guide

Unlocking a Mutex

Use pthread_mutex_unlock(3C) to unlock the mutex pointed to by mutex.

pthread_mutex_unlock Syntax

int pthread_mutex_unlock(pthread_mutex_t *mutex); 
#include <pthread.h>

pthread_mutex_t mutex;
int ret;

ret = pthread_mutex_unlock(&mutex); /* release the mutex */

pthread_mutex_unlock() releases the mutex object referenced by mutex. The manner in which a mutex is released is dependent upon the mutex's type attribute. If threads are blocked on the mutex object when pthread_mutex_unlock() is called and the mutex becomes available, the scheduling policy determines which thread acquires the mutex. For PTHREAD_MUTEX_RECURSIVE mutexes, the mutex becomes available when the count reaches zero and the calling thread no longer has any locks on this mutex.

pthread_mutex_unlock Return Values

pthread_mutex_unlock() returns zero after completing successfully. Any other return value indicates that an error occurred. When the following condition occurs, the function fails and returns the corresponding value.



The current thread does not own the mutex.