Referring to the functionality given by pthread_mutex_lock is false that:
pthread_mutex_lock
Two threads can be used simultaneously without using unlock.
unlock
It can block the thread that invokes the mutex
It can unblock a thread that invokes the mutex
It is used to limite the concurrency with unlock
Referring to pthread_mutex_unlock is false that:
pthread_mutex_unlock
It is blocking
It is not blocking
It requires that the invoking thread has the mutex (previously taken with a pthread_mutex_lock)
It is used with a lock to limit concurrency
lock