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PTHREAD_MUTEXATTR_GETPROTOCPOSIX)Programmer'sPTHREAD_MUTEXATTR_GETPROTOCOL(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_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  protocol 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  subject  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  dif-
       ferent  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  ini-
       tialized    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  implementation  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, 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_GETPROTOCOL(3P)