Tribblix: manual page: pthread_mutex

PTHREAD_MUTEX_INIT(3C) Standard C Library Functions PTHREAD_MUTEX_INIT(3C)

NAME

pthread_mutex_init, pthread_mutex_destroy - initialize or destroy a
mutex

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);

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t ecmutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
pthread_mutex_t rmutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

DESCRIPTION

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.

Except for robust mutexes, 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.

In cases where error checking mutex attributes are appropriate, the
macro PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP 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 initialized with pthread_mutexattr_init(3C) and its type set to
PTHREAD_MUTEX_ERRORCHECK.

In cases where recursive mutex attributes are appropriate, the macro
PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP 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 initialized with pthread_mutexattr_init(3C) and its type set to
PTHREAD_MUTEX_RECURSIVE.

RETURN VALUES

If successful, the pthread_mutex_init() and pthread_mutex_destroy()
functions return 0. Otherwise, an error number is returned to indicate
the error.

ERRORS

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 a robust
mutex previously initialized but not yet destroyed.
See pthread_mutexattr_setrobust(3C).

EINVAL An attempt was detected to re-initialize a robust
mutex previously initialized with a different set of
attributes. See pthread_mutexattr_setrobust(3C).

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.

INTERFACE STABILITY