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Pthread Library
HP-UX 11i Version 3: February 2007

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pthread_mutex_init(), pthread_mutex_destroy() — initialize or destroy a mutex


#include <pthread.h>

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

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

int pthread_mutex_destroy( pthread_mutex_t *mutex );



Pointer to the mutex to be initialized or destroyed.


Pointer to the attributes object that defines the characteristics of the mutex to be initialized. If the pointer is NULL, default attributes are used.


The pthread_mutex_init() function initializes the mutex referenced by mutex with the attributes attr. If the parameter attr is NULL, the default mutex attributes are used. See pthread_mutexattr_init(3T) for a list of default mutex attributes. After successful initialization, the mutex is initialized, unlocked, and ready to be used in mutex operations. A mutex should be initialized only once or the resulting behavior is undefined. The pthread_once() function provides a way to ensure that a mutex is initialized only once.

The macro PTHREAD_MUTEX_INITIALIZER can be used to initialize mutexes that are statically allocated. These mutexes will be initialized with default attributes. The pthread_mutex_init() function does not need to be called for statically initialized mutexes.

If the process-shared attribute in the mutex attributes object referenced by attr is defined as PTHREAD_PROCESS_SHARED, the mutex must be allocated such that the processes sharing the mutex have access to it. This may be done through the memory-mapping functions (see mmap(2)) or the shared memory functions (see shmget(2)).

The pthread_mutex_destroy() function destroys the mutex referenced by mutex. This function may set mutex to an invalid value. The destroyed mutex can be reinitialized using the function pthread_mutex_init(). If the mutex is used after destruction in any mutex call, the resulting behavior is undefined.

A mutex should be destroyed only when it is unlocked. Destroying a mutex that is currently being used results in undefined behavior.


Upon successful completion, pthread_mutex_init() and pthread_mutex_destroy() return zero. Otherwise, an error number is returned to indicate the error (the errno variable is not set).


If any of the following occur, the pthread_mutex_init() function returns the corresponding error number:


The necessary resources (other than memory) to initialize mutex were not available.


mutex is an already initialized mutex. However, getting EBUSY for reinitializing the mutex cannot be expected all the time since the behavior of reinitializing the mutex is undefined.


mutex points to an illegal address.


The value specified by mutex or attr is invalid.


There is insufficient memory available in which to initialize mutex.


The caller does not have the necessary permission to perform the mutex initialization.

If any of the following occur, the pthread_mutex_destroy() function returns the corresponding error number:


mutex is currently locked or in use by another thread.


mutex is not a valid mutex.


The space for the mutex must be allocated before calling pthread_mutex_init(). Undefined behavior will result if the process-shared attribute of attr is PTHREAD_PROCESS_SHARED and the space allocated for the mutex is not accessible to cooperating threads.


pthread_mutex_init() and pthread_mutex_destroy() were derived from the IEEE POSIX P1003.1c standard.


pthread_mutex_lock(3T), pthread_mutex_trylock(3T), pthread_mutex_unlock(3T).


pthread_mutex_init(): POSIX 1003.1c. pthread_mutex_destroy(): POSIX 1003.1c.

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