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


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;


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,
except that no error checks are performed.

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.


ATTRIBUTES


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


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO


pthread_cond_wait(3C), pthread_mutex_lock(3C),
pthread_mutexattr_setprioceiling(3C), pthread_mutexattr_setprotocol(3C),
pthread_mutexattr_setpshared(3C), pthread_mutexattr_setrobust(3C),
pthread_mutexattr_settype(3C), attributes(5), mutex(5), standards(5)


November 11, 2008 PTHREAD_MUTEX_INIT(3C)