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 initialization, 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(3THR).

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_RECURSIVE.

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. This condition is not reported.

EINVAL

The value specified by attr or mutex is invalid. This condition is not reported.

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(3THR) or pthread_cond_timedwait(3THR)) by another thread. This condition is not reported.

EINVAL

The value specified by mutex is invalid. This condition is not reported.

See attributes(5) for descriptions of the following attributes:

mutex(3THR), pthread_cond_timedwait(3THR), pthread_cond_wait(3THR), pthread_mutex_getprioceiling(3THR), pthread_mutex_lock(3THR), pthread_mutex_unlock(3THR), pthread_mutex_setprioceiling(3THR), pthread_mutex_trylock(3THR), pthread_mutexattr_init(3THR), pthread_mutexattr_getpshared(3THR), pthread_mutexattr_setpshared(3THR) attributes(5), standards(5)