PTHREAD_MUTEXATTR(3)

NAME
pthread_mutexattr_destroy, pthread_mutexattr_getprioceiling, pthread_mutexattr_getprotocol, pthread_mutexattr_gettype, pthread_mutexattr_init, pthread_mutexattr_setprioceiling, pthread_mutexattr_setprotocol, pthread_mutexattr_settype - mutex attribute operations

SYNOPSIS
#include <pthread.h>
int
pthread_mutexattr_destroy(pthread_mutexattr_t *attr);
int
pthread_mutexattr_getprioceiling(const pthread_mutexattr_t *restrict attr, int *restrict prioceiling);
int
pthread_mutexattr_getprotocol(const pthread_mutexattr_t *restrict attr, int *restrict protocol);
int
pthread_mutexattr_gettype(const pthread_mutexattr_t *restrict attr, int *restrict type);
int
pthread_mutexattr_init(pthread_mutexattr_t *attr);
int
pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr, int prioceiling);
int
pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr, int protocol);
int
pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);

DESCRIPTION
Mutex attributes are used to specify parameters to pthread_mutex_init(). One attribute object can be used in multiple calls to pthread_mutex_init(), with or without modifications between calls.

The pthread_mutexattr_init() function initializes attr with all of the default mutex attributes.

The pthread_mutexattr_destroy() function destroys attr.

The pthread_mutexattr_settype() function sets the mutex type value of the attribute. Valid mutex types are: PTHREAD_MUTEX_NORMAL, PTHREAD_MUTEX_ERRORCHECK, PTHREAD_MUTEX_RECURSIVE, and PTHREAD_MUTEX_DEFAULT. The default mutex type for pthread_mutexattr_init() is PTHREAD_MUTEX_DEFAULT.

PTHREAD_MUTEX_NORMAL mutexes do not check for usage errors. PTHREAD_MUTEX_NORMAL mutexes will deadlock if reentered, and result in undefined behavior if a locked mutex is unlocked by another thread. Attempts to unlock an already unlocked PTHREAD_MUTEX_NORMAL mutex will result in undefined behavior.

PTHREAD_MUTEX_ERRORCHECK mutexes do check for usage errors. If an attempt is made to relock a PTHREAD_MUTEX_ERRORCHECK mutex without first dropping the lock, an error will be returned. If a thread attempts to unlock a PTHREAD_MUTEX_ERRORCHECK mutex that is locked by another thread, an error will be returned. If a thread attempts to unlock a PTHREAD_MUTEX_ERRORCHECK thread that is unlocked, an error will be returned.

PTHREAD_MUTEX_RECURSIVE mutexes allow recursive locking. An attempt to relock a PTHREAD_MUTEX_RECURSIVE mutex that is already locked by the same thread succeeds. An equivalent number of pthread_mutex_unlock(3) calls are needed before the mutex will wake another thread waiting on this lock. If a thread attempts to unlock a PTHREAD_MUTEX_RECURSIVE mutex that is locked by another thread, an error will be returned. If a thread attemps to unlock a PTHREAD_MUTEX_RECURSIVE thread that is unlocked, an error will be returned.

PTHREAD_MUTEX_DEFAULT mutexes result in undefined behavior if reentered. Unlocking a PTHREAD_MUTEX_DEFAULT mutex locked by another thread will result in undefined behavior. Attempts to unlock an already unlocked PTHREAD_MUTEX_DEFAULT mutex will result in undefined behavior.

pthread_mutexattr_gettype() functions copy the type value of the attribute to the location pointed to by the second parameter.

The pthread_mutexattr_set*() functions set the attribute that corresponds to each function name.

The pthread_mutexattr_get*() functions copy the value of the attribute that corresponds to each function name to the location pointed to by the second function parameter.

RETURN VALUES
If successful, these functions return 0. Otherwise, an error number is returned to indicate the error.

ERRORS
pthread_mutexattr_init() will fail if:

[ENOMEM]
    Out of memory.

pthread_mutexattr_destroy() will fail if:

[EINVAL]
    Invalid value for attr.

pthread_mutexattr_setprioceiling() will fail if:

[EINVAL]
    Invalid value for attr, or invalid value for prioceiling.

pthread_mutexattr_getprioceiling() will fail if:

[EINVAL]
    Invalid value for attr.

pthread_mutexattr_setprotocol() will fail if:

[EINVAL]
    Invalid value for attr, or invalid value for protocol.

pthread_mutexattr_getprotocol() will fail if:

[EINVAL]
    Invalid value for attr.

pthread_mutexattr_settype() will fail if:

[EINVAL]
    Invalid value for attr, or invalid value for type.

pthread_mutexattr_gettype() will fail if:

[EINVAL]
    Invalid value for attr.

SEE ALSO
pthread_mutex_init(3)

STANDARDS
pthread_mutexattr_init() and pthread_mutexattr_destroy() conform to p1003.1-96

pthread_mutexattr_setprioceiling(), pthread_mutexattr_getprioceiling(), pthread_mutexattr_setprotocol(), pthread_mutexattr_getprotocol(), pthread_mutexattr_settype(), and pthread_mutexattr_gettype() conform to susv2