pthread_mutexattr_init

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)