NAME
pthread_mutexattr_init, pthread_mutexattr_destroy,
pthread_mutexattr_settype, pthread_mutexattr_gettype - mutex creation
attributes
SYNOPSIS
#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);
DESCRIPTION
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.
RETURN VALUE
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.
ERRORS
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
AUTHOR
Xavier Leroy <Xavier.Leroy@inria.fr>
SEE ALSO
pthread_mutex_init(3), pthread_mutex_lock(3), pthread_mutex_unlock(3).
LinuxThreads PTHREAD_MUTEXATTR(3)