PTHREAD_MUTEXATTR_GETPROTOCOL(3P)                   POSIX Programmer's Manual                  PTHREAD_MUTEXATTR_GETPROTOCOL(3P)



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

NAME
       pthread_mutexattr_getprotocol, pthread_mutexattr_setprotocol - get and set the protocol attribute of the mutex attributes
       object (REALTIME THREADS)

SYNOPSIS
       #include <pthread.h>

       int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *
              restrict attr, int *restrict protocol);
       int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr,
              int protocol);




DESCRIPTION
       The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol() functions, respectively, shall get  and  set  the
       protocol  attribute  of  a  mutex  attributes  object  pointed  to  by  attr which was previously created by the function
       pthread_mutexattr_init().

       The protocol attribute defines the protocol to be followed in utilizing mutexes. The value of protocol may be one of:

       PTHREAD_PRIO_NONE

       PTHREAD_PRIO_INHERIT


       PTHREAD_PRIO_PROTECT


       which are defined in the <pthread.h> header.

       When a thread owns a mutex with the PTHREAD_PRIO_NONE protocol attribute,  its  priority  and  scheduling  shall  not  be
       affected by its mutex ownership.

       When  a  thread  is  blocking higher priority threads because of owning one or more mutexes with the PTHREAD_PRIO_INHERIT
       protocol attribute, it shall execute at the higher of its priority or the priority of the highest priority thread waiting
       on any of the mutexes owned by this thread and initialized with this protocol.

       When a thread owns one or more mutexes initialized with the PTHREAD_PRIO_PROTECT protocol, it shall execute at the higher
       of its priority or the highest of the priority ceilings of all the mutexes owned by this thread and initialized with this
       attribute, regardless of whether other threads are blocked on any of these mutexes or not.

       While a thread is holding a mutex which has been initialized with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT proto-
       col attributes, it shall not be subject to being moved to the tail of the scheduling queue at its priority in  the  event
       that  its  original  priority is changed, such as by a call to sched_setparam().  Likewise, when a thread unlocks a mutex
       that has been initialized with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol attributes, it shall not be sub-
       ject  to  being  moved  to  the  tail  of the scheduling queue at its priority in the event that its original priority is
       changed.

       If a thread simultaneously owns several mutexes initialized with different protocols, it shall execute at the highest  of
       the priorities that it would have obtained by each of these protocols.

       When  a  thread  makes  a  call to pthread_mutex_lock(), the mutex was initialized with the protocol attribute having the
       value PTHREAD_PRIO_INHERIT, when the calling thread is blocked because the mutex is owned by another thread,  that  owner
       thread  shall  inherit the priority level of the calling thread as long as it continues to own the mutex. The implementa-
       tion shall update its execution priority to the maximum of its assigned priority and all its inherited  priorities.  Fur-
       thermore,  if  this  owner  thread itself becomes blocked on another mutex, the same priority inheritance effect shall be
       propagated to this other owner thread, in a recursive manner.

RETURN VALUE
       Upon successful completion,  the  pthread_mutexattr_getprotocol()  and  pthread_mutexattr_setprotocol()  functions  shall
       return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS
       The pthread_mutexattr_setprotocol() function shall fail if:

       ENOTSUP
              The value specified by protocol is an unsupported value.


       The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol() functions may fail if:

       EINVAL The value specified by attr or protocol is invalid.

       EPERM  The caller does not have the privilege to perform the operation.


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

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       pthread_cond_destroy(),  pthread_create(),  pthread_mutex_destroy(), 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                             PTHREAD_MUTEXATTR_GETPROTOCOL(3P)