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