pthread_mutex_consistent_np() returns zero after completing successfully. Any other returned value indicates that an error occurred. When any of the following conditions occurs, the function fails and returns the corresponding value.
pthread_mutex_consistent_np() fails if:
The option _POSIX_THREAD_PRIO_INHERIT is not defined or the implementation does not support pthread_mutex_consistent_np().
pthread_mutex_consistent_np() might fail if: