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PTHREAD_MUTEXATTR_GETTYPE(3POSIX Programmer's ManPTHREAD_MUTEXATTR_GETTYPE(3P)

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(3P)