pthread_mutex_trylock(3) [netbsd man page]
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
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pthread_mutex_init(3C) pthread_mutex_init(3C) NAME
pthread_mutex_init, pthread_mutex_destroy - initialize or destroy a mutex SYNOPSIS
cc -mt [ flag... ] file... -lpthread [ library... ] #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); pthread_mutex_t mutex= PTHREAD_MUTEX_INITIALIZER The pthread_mutex_init() function initializes the mutex referenced by mutex with attributes specified by attr. If attr is NULL, the default mutex attributes are used; the effect is the same as passing the address of a default mutex attributes object. Upon successful ini- tialization, the state of the mutex becomes initialized and unlocked. Attempting to initialize an already initialized mutex results in undefined behavior. The pthread_mutex_destroy() function destroys the mutex object referenced by mutex; the mutex object becomes, in effect, uninitialized. A destroyed mutex object can be re-initialized using pthread_mutex_init(); the results of otherwise referencing the object after it has been destroyed are undefined. It is safe to destroy an initialized mutex that is unlocked. Attempting to destroy a locked mutex results in undefined behavior. In cases where default mutex attributes are appropriate, the macro PTHREAD_MUTEX_INITIALIZER can be used to initialize mutexes that are statically allocated. The effect is equivalent to dynamic initialization by a call to pthread_mutex_init() with parameter attr specified as NULL, except that no error checks are performed. If successful, the pthread_mutex_init() and pthread_mutex_destroy() functions return 0. Otherwise, an error number is returned to indicate the error. The pthread_mutex_init() function will fail if: EAGAIN The system lacked the necessary resources (other than memory) to initialize another mutex. EBUSY An attempt was detected to re-initialize the object referenced by mutex, a robust mutex previously initialized but not yet destroyed. EINVAL The value specified by attr has not been initialized using pthread_mutexattr_init(3C). EINVAL An attempt was made to initialize mutex to be robust and not PTHREAD_PRIO_INHERIT. EINVAL An attempt was made to initalize mutex to be PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT and the type of the mutex to be PTHREAD_MUTEX_ERRORCHECK or PTHREAD_MUTEX_RECURSIVE. EINVAL An attpemt was made to initalize mutex to be PTHREAD_PROCESS_SHARED and the type of the mutex to be PTHREAD_MUTEX_RECUR- SIVE. EINVAL The process-shared attribute associated with attr is invalid. ENOMEM Insufficient memory exists to initialize the mutex. EPERM The caller does not have the privilege to perform the operation. The pthread_mutex_init() function may fail if: EBUSY An attempt was detected to re-initialize the object referenced by mutex, a mutex previously initialized but not yet destroyed. EINVAL The value specified by attr or mutex is invalid. The pthread_mutex_destroy() function may fail if: EBUSY An attempt was detected to destroy the object referenced by mutex while it is locked or referenced (for example, while being used in a pthread_cond_wait(3C) or pthread_cond_timedwait(3C)) by another thread. EINVAL The value specified by mutex is invalid. See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ pthread_cond_timedwait(3C), pthread_cond_wait(3C), pthread_mutex_getprioceiling(3C), pthread_mutex_lock(3C), pthread_mutex_unlock(3C), pthread_mutex_setprioceiling(3C), pthread_mutex_trylock(3C), pthread_mutexattr_init(3C), pthread_mutexattr_getpshared(3C), pthread_mutex- attr_setpshared(3C) attributes(5), mutex(5), standards(5) 23 Mar 2005 pthread_mutex_init(3C)