If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows: Return Description 0 Successful completion. [EINVAL] The value specified by cond or mutex is invalid, or Different mutexes are supplied for concurrent pthread_cond_wait() or pthread_cond_timedwait() operations on the same condition variable, or The mutex was not owned by the calling thread at the time of the call. [ENOMEM] The Threads Library cannot acquire memory needed to block using a statically initialized condition variable.