pthread_mutexattr_gettype

PTHREAD_MUTEXATTR(3)                                      PTHREAD_MUTEXATTR(3)



NAME
       pthread_mutexattr_init,    pthread_mutexattr_destroy,    pthread_mutex-
       attr_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 stan-
       dard 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_mutex-
       attr_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_RECUR-
              SIVE_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)