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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_INHERIT
       PTHREAD_PRIO_NONE
       PTHREAD_PRIO_PROTECT
       which are defined in the <pthread.h> header. The default value  of  the
       attribute shall be PTHREAD_PRIO_NONE.
       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  robust  mutexes  with   the   PTHREAD_PRIO_INHERIT   protocol
       attribute, it shall execute at the higher of its priority or the prior-
       ity of the highest priority thread waiting on any of the robust mutexes
       owned by this thread and initialized with this protocol.
       When a thread is blocking higher priority threads because of owning one
       or more  non-robust  mutexes  with  the  PTHREAD_PRIO_INHERIT  protocol
       attribute, it shall execute at the higher of its priority or the prior-
       ity of the highest priority thread waiting on  any  of  the  non-robust
       mutexes owned by this thread and initialized with this protocol.
       When  a  thread  owns  one  or more robust 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 robust
       mutexes owned by this  thread  and  initialized  with  this  attribute,
       regardless  of whether other threads are blocked on any of these robust
       mutexes or not.
       When a thread owns one or more non-robust 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  non-robust
       mutexes  owned  by  this  thread  and  initialized with this attribute,
       regardless of whether other threads are blocked on any  of  these  non-
       robust 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.
       Furthermore, if this owner thread itself  becomes  blocked  on  another
       mutex    with    the    protocol    attribute    having    the    value
       PTHREAD_PRIO_INHERIT, the same priority  inheritance  effect  shall  be
       propagated to this other owner thread, in a recursive manner.
       The  behavior  is undefined if the value specified by the attr argument
       to pthread_mutexattr_getprotocol()  or  pthread_mutexattr_setprotocol()
       does not refer to an initialized mutex attributes object.
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 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
       If an implementation detects that the value specified by the attr argu-
       ment  to pthread_mutexattr_getprotocol() or pthread_mutexattr_setproto-
       col() does not refer to an initialized mutex attributes object,  it  is
       recommended that the function should fail and report an [EINVAL] error.
FUTURE DIRECTIONS
       None.
SEE ALSO
       pthread_cond_destroy(), pthread_create(), pthread_mutex_destroy()
       The Base Definitions volume of POSIX.1-2008, <pthread.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013    PTHREAD_MUTEXATTR_GETPROTOCOL(3P)