pthread_mutex_unlock(3) [osf1 man page]

pthread_mutex_unlock(3) 				     Library Functions Manual					   pthread_mutex_unlock(3)

NAME

       pthread_mutex_unlock - Unlocks the specified mutex.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int   pthread_mutex_unlock(
			      pthread_mutex_t	*mutex);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS

       Mutex to be unlocked.

DESCRIPTION

       This routine unlocks the mutex specified by the mutex argument.

       This  routine  behaves  as  follows,  based on the type of the specified mutex: For a normal, default, or errorcheck mutex: if the mutex is
       owned by the calling thread, it is unlocked with no current owner.  Further, for a normal or default mutex: if the mutex is not	locked	or
       is locked by another thread, this routine can also return [EPERM], but this is not guaranteed. For an errorcheck mutex: if the mutex is not
       locked or is locked by another thread, this routine returns [EPERM].  For a recursive mutex: if the mutex is owned by the  calling  thread,
       the  lock count is decremented. The mutex remains locked and owned until the lock count reaches zero (0). When the lock count reaches zero,
       the mutex becomes unlocked with no current owner.

       If one or more threads are waiting to lock the specified mutex, and the mutex becomes unlocked, this routine causes one thread  to  unblock
       and  to	try  to  acquire  the mutex.  The scheduling policy is used to determine which thread to unblock.  For the SCHED_FIFO and SCHED_RR
       policies, a blocked thread is chosen in priority order, using first-in/first-out within priorities.  Note  that	the  mutex  might  not	be
       acquired by the awakened thread if any other running thread attempts to lock the mutex first.

       On  Tru64  UNIX,  if a signal is delivered to a thread waiting for a mutex, upon return from the signal handler, the thread resumes waiting
       for the mutex as if it was not interrupted.

RETURN VALUES

       If an error condition occurs, this routine returns an integer value indicating the type of error.  Possible return values are  as  follows:
       Successful completion.  The value specified for mutex is invalid.  The calling thread does not own the mutex.

ERRORS

       None

RELATED INFORMATION

       Functions: pthread_mutexattr_settype(3), pthread_mutex_destroy(3), pthread_mutex_init(3), pthread_mutex_lock(3), pthread_mutex_trylock(3)

       Manuals: Guide to DECthreads and Programmer's Guide

       delim off

															   pthread_mutex_unlock(3)

PTHREAD_MUTEX(3)					   BSD Library Functions Manual 					  PTHREAD_MUTEX(3)

NAME

     pthread_mutex -- mutual exclusion primitives

LIBRARY

     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

     #include <pthread.h>

     int
     pthread_mutex_init(pthread_mutex_t * restrict mutex, const pthread_mutexattr_t * restrict attr);

     int
     pthread_mutex_destroy(pthread_mutex_t *mutex);

     int
     pthread_mutex_lock(pthread_mutex_t *mutex);

     int
     pthread_mutex_trylock(pthread_mutex_t *mutex);

     int
     pthread_mutex_unlock(pthread_mutex_t *mutex);

     pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

DESCRIPTION

     The pthread_mutex_init() function creates a new mutex, with attributes specified with attr.  If attr is NULL, the default attributes are
     used.

     The macro PTHREAD_MUTEX_INITIALIZER can be used to initialize a mutex when the default attributes are appropriate and the mutex can be stati-
     cally allocated.  The behavior is similar to pthread_mutex_init() with attr specified as NULL, except that no error checking is done.

     The pthread_mutex_destroy() function frees the resources allocated for mutex.  It is possible to reinitialize a destroyed mutex, but unde-
     fined behavior may follow if the destroyed object is otherwise referenced.

     The pthread_mutex_lock() function locks mutex.  If the mutex is already locked, the calling thread will block until the mutex becomes avail-
     able.  The error conditions may vary depending on the type of the mutex; see pthread_mutexattr(3) for additional details.

     The pthread_mutex_trylock() function locks mutex.	If the mutex is already locked, pthread_mutex_trylock() will not block waiting for the
     mutex, but will return an error condition.

     The pthread_mutex_unlock() function unlocks an acquired mutex.  When operating with the default mutex type, undefined behavior follows if a
     thread tries to unlock a mutex that has not been locked by it, or if a thread tries to release a mutex that is already unlocked.

RETURN VALUES

     Upon success all described functions return zero.	Otherwise, an error number will be returned to indicate the error.

ERRORS

     pthread_mutex_init() may fail if:

     [EAGAIN]		The system lacks the resources to initialize another mutex.

     [EINVAL]		The value specified by attr is invalid.

     [ENOMEM]		The process cannot allocate enough memory to initialize another mutex.

     pthread_mutex_destroy() may fail if:

     [EBUSY]		Mutex is locked by another thread.

     [EINVAL]		The value specified by mutex is invalid.

     pthread_mutex_lock() may fail if:

     [EDEADLK]		A deadlock would occur if the thread blocked waiting for mutex.

     [EINVAL]		The value specified by mutex is invalid.

     pthread_mutex_trylock() may fail if:

     [EBUSY]		Mutex is already locked.

     [EINVAL]		The value specified by mutex is invalid.

     pthread_mutex_unlock() may fail if:

     [EINVAL]		The value specified by mutex is invalid.

     [EPERM]		The current thread does not hold a lock on mutex.

SEE ALSO

     pthread(3), pthread_barrier(3), pthread_cond(3), pthread_mutexattr(3), pthread_rwlock(3), pthread_spin(3)

STANDARDS

     These functions conform to IEEE Std 1003.1-2001 (``POSIX.1'').

BSD
								   July 8, 2010 							       BSD