Waits on the condition variable.
#include <pthread.h>
int pthread_cond_wait (
pthread_cond_t *cond,
pthread_mutex_t *mutex);
(IN) Points to the condition variable to wait on.
(IN) Points to a mutually exclusive lock held by the calling thread.
If successful, returns zero; otherwise, returns an nonzero error code:
The pthread_cond_wait function atomically releases the entry lock pointed to by mutex and blocks the calling thread. When the condition is signaled, pthread_cond_wait returns.
It is the responsibility of the calling thread to re-evaluate the entry condition when pthread_cond_wait returns. The condition may have been consumed by a different thread between the time when a blocked thread within pthread_cond_wait awakens and when it acquires the entry mutex.
The wait can be interrupted, in which case pthread_cond_wait returns EINTR. In this case, the entry lock is not held when pthread_cond_wait returns.