NAME

    pthread_mutex_unlock - Unlocks a mutex

 SYNOPSIS

     #include <pthread.h>

     int pthread_mutex_unlock( pthread_mutex_t *mutex );

 PARAMETERS

     mutex                Mutex that is unlocked.

 DESCRIPTION

 The pthread_mutex_unlock() routine unlocks a mutex. If no threads are
 waiting for the mutex, the mutex unlocks with no current owner. If one
 or more threads are waiting to lock the specified mutex, this routine
 causes one thread to return from its call to pthread_mutex_lock(). The
 scheduling policy is used to determine which thread acquires the mutex.
 For the SCHED_FIFO and  SCHED_RR policies, a blocked thread is chosen in
 priority order.

 The results of calling this routine are unpredictable if the mutex
 specified in mutex is unlocked. The results of calling this routine are
 also unpredictable if the mutex specified in mutex is currently owned by
 a thread other than the calling thread.

 RETURN VALUES

 If the function fails, errno may be set to one of the following values:

    Return   Error      Description
    ____________________________________________________________
     0                  Successful completion.

    -1      [EINVAL]    The value specified by mutex is invalid.

 RELATED INFORMATION

     FUNCTIONS:  pthread_mutexattr_setkind_np
                 pthread_mutex_destroy
                 pthread_mutex_init
                 pthread_mutex_lock
                 pthread_mutex_trylock
                 pthread_unlock_global_np