pthread_mutexattr_init, pthread_mutexattr_destroy, pthread_mutexattr_settype,
pthread_mutexattr_gettype - mutex creation attributes
#include <pthread.h>
int pthread_mutexattr_init(pthread_mutexattr_t *attr);
int pthread_mutexattr_destroy(pthread_mutexattr_t *attr);
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int
kind);
int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr,
int *kind);
Mutex attributes can be specified at mutex creation time, by passing a mutex
attribute object as second argument to
pthread_mutex_init(3). Passing
NULL is equivalent to passing a mutex attribute object with all
attributes set to their default values.
pthread_mutexattr_init initializes the mutex attribute object
attr
and fills it with default values for the attributes.
pthread_mutexattr_destroy destroys a mutex attribute object, which must
not be reused until it is reinitialized.
pthread_mutexattr_destroy does
nothing in the LinuxThreads implementation.
LinuxThreads supports only one mutex attribute: the mutex kind, which is either
PTHREAD_MUTEX_FAST_NP for ``fast'' mutexes,
PTHREAD_MUTEX_RECURSIVE_NP for ``recursive'' mutexes, or
PTHREAD_MUTEX_ERRORCHECK_NP for ``error checking'' mutexes. As the
NP suffix indicates, this is a non-portable extension to the POSIX
standard and should not be employed in portable programs.
The mutex kind determines what happens if a thread attempts to lock a mutex it
already owns with
pthread_mutex_lock(3). If the mutex is of the
``fast'' kind,
pthread_mutex_lock(3) simply suspends the calling thread
forever. If the mutex is of the ``error checking'' kind,
pthread_mutex_lock(3) returns immediately with the error code
EDEADLK. If the mutex is of the ``recursive'' kind, the call to
pthread_mutex_lock(3) returns immediately with a success return code.
The number of times the thread owning the mutex has locked it is recorded in
the mutex. The owning thread must call
pthread_mutex_unlock(3) the same
number of times before the mutex returns to the unlocked state.
The default mutex kind is ``fast'', that is,
PTHREAD_MUTEX_FAST_NP.
pthread_mutexattr_settype sets the mutex kind attribute in
attr to
the value specified by
kind.
pthread_mutexattr_gettype retrieves the current value of the mutex kind
attribute in
attr and stores it in the location pointed to by
kind.
pthread_mutexattr_init,
pthread_mutexattr_destroy and
pthread_mutexattr_gettype always return 0.
pthread_mutexattr_settype returns 0 on success and a non-zero error code
on error.
On error,
pthread_mutexattr_settype returns the following error code:
- EINVAL
-
kind is neither PTHREAD_MUTEX_FAST_NP nor
PTHREAD_MUTEX_RECURSIVE_NP nor PTHREAD_MUTEX_ERRORCHECK_NP
Xavier Leroy <
[email protected]>
pthread_mutex_init(3),
pthread_mutex_lock(3),
pthread_mutex_unlock(3).