PTHREAD_MUTEXATTR(3)					     Library Functions Manual					      PTHREAD_MUTEXATTR(3)

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)