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()  functions,  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() functions 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_RECURSIVE  mutex  with
       condition  variables  because the implicit unlock performed 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 predicate.

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 .