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PTHREAD_MUTEXATTR_GETTYPE(PPOSIX Programmer's ManuPTHREAD_MUTEXATTR_GETTYPE(P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       pthread_mutexattr_gettype, pthread_mutexattr_settype - get and set  the
       mutex type attribute

SYNOPSIS
       #include <pthread.h>

       int pthread_mutexattr_gettype(const pthread_mutexattr_t *restrict attr,
	      int *restrict type);
       int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);

DESCRIPTION
       The  pthread_mutexattr_gettype()	 and pthread_mutexattr_settype() func‐
       tions, respectively, shall get and set the mutex type  attribute.  This
       attribute  is set in the type parameter to these functions. The default
       value of the type attribute is PTHREAD_MUTEX_DEFAULT.

       The type of mutex is contained in  the  type  attribute	of  the	 mutex
       attributes. Valid mutex types include:

       PTHREAD_MUTEX_NORMAL

	      This type of mutex does not detect deadlock. A thread attempting
	      to relock this mutex without first unlocking it shall  deadlock.
	      Attempting  to  unlock  a	 mutex	locked	by  a different thread
	      results in undefined behavior. Attempting to unlock an  unlocked
	      mutex results in undefined behavior.

       PTHREAD_MUTEX_ERRORCHECK

	      This  type of mutex provides error checking. A thread attempting
	      to relock this mutex without first  unlocking  it	 shall	return
	      with  an	error.	A  thread  attempting  to unlock a mutex which
	      another thread has locked shall return with an error.  A	thread
	      attempting  to  unlock  an  unlocked  mutex shall return with an
	      error.

       PTHREAD_MUTEX_RECURSIVE

	      A thread attempting to relock this mutex without first unlocking
	      it  shall	 succeed  in locking the mutex. The relocking deadlock
	      which can occur with mutexes of type PTHREAD_MUTEX_NORMAL cannot
	      occur  with  this	 type  of  mutex. Multiple locks of this mutex
	      shall require the same number of unlocks to  release  the	 mutex
	      before another thread can acquire the mutex. A thread attempting
	      to unlock a mutex which another thread has locked	 shall	return
	      with  an error.  A thread attempting to unlock an unlocked mutex
	      shall return with an error.

       PTHREAD_MUTEX_DEFAULT

	      Attempting to recursively lock a mutex of this type  results  in
	      undefined	 behavior.  Attempting	to unlock a mutex of this type
	      which was not locked by the calling thread results in  undefined
	      behavior.	  Attempting  to  unlock a mutex of this type which is
	      not locked results in undefined behavior. An implementation  may
	      map this mutex to one of the other mutex types.

RETURN VALUE
       Upon  successful	 completion,  the pthread_mutexattr_gettype() function
       shall return zero and store the value of the  type  attribute  of  attr
       into  the  object referenced by the type parameter. Otherwise, an error
       shall be returned to indicate the error.

       If successful, the pthread_mutexattr_settype()  function	 shall	return
       zero;  otherwise,  an  error  number  shall be returned to indicate the
       error.

ERRORS
       The pthread_mutexattr_settype() function shall fail if:

       EINVAL The value type is invalid.

       The pthread_mutexattr_gettype() and  pthread_mutexattr_settype()	 func‐
       tions may fail if:

       EINVAL The value specified by attr is invalid.

       These functions shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       It is advised that an application should not use a PTHREAD_MUTEX_RECUR‐
       SIVE mutex with condition variables because the	implicit  unlock  per‐
       formed  for  a  pthread_cond_timedwait() or pthread_cond_wait() may not
       actually release the mutex (if it had been locked multiple  times).  If
       this  happens,  no other thread can satisfy the condition of the predi‐
       cate.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       pthread_cond_timedwait()	  ,   the   Base   Definitions	  volume    of
       IEEE Std 1003.1-2001, <pthread.h>

COPYRIGHT
       Portions	 of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating	System	Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003	by  the	 Institute  of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained	online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003	  PTHREAD_MUTEXATTR_GETTYPE(P)
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