pthread_mutexattr_setprotocol(3p)

1PTHREAD_MUTEXATTR_GETPROTOCOPLO(S3IPX)Programmer'sPMTaHnRuEaAlD_MUTEXATTR_GETPROTOCOL(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       pthread_mutexattr_getprotocol, pthread_mutexattr_setprotocol - get  and
13       set  the  protocol  attribute  of the mutex attributes object (REALTIME
14       THREADS)
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SYNOPSIS

17       #include <pthread.h>
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19       int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *
20              restrict attr, int *restrict protocol);
21       int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr,
22              int protocol);
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DESCRIPTION

28       The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol()
29       functions,  respectively, shall get and set the protocol attribute of a
30       mutex attributes object pointed to by attr which was previously created
31       by the function pthread_mutexattr_init().
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33       The protocol attribute defines the protocol to be followed in utilizing
34       mutexes. The value of protocol may be one of:
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36       PTHREAD_PRIO_NONE
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38       PTHREAD_PRIO_INHERIT
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41       PTHREAD_PRIO_PROTECT
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44       which are defined in the <pthread.h> header.
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46       When  a  thread  owns  a  mutex  with  the  PTHREAD_PRIO_NONE  protocol
47       attribute,  its  priority  and  scheduling shall not be affected by its
48       mutex ownership.
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50       When a thread is blocking higher priority threads because of owning one
51       or  more  mutexes  with the PTHREAD_PRIO_INHERIT protocol attribute, it
52       shall execute at the higher of its priority  or  the  priority  of  the
53       highest  priority  thread  waiting  on any of the mutexes owned by this
54       thread and initialized with this protocol.
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56       When  a  thread  owns  one  or  more  mutexes  initialized   with   the
57       PTHREAD_PRIO_PROTECT  protocol,  it  shall execute at the higher of its
58       priority or the highest of the priority ceilings  of  all  the  mutexes
59       owned by this thread and initialized with this attribute, regardless of
60       whether other threads are blocked on any of these mutexes or not.
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62       While a thread is holding a mutex which has been initialized  with  the
63       PTHREAD_PRIO_INHERIT  or  PTHREAD_PRIO_PROTECT  protocol attributes, it
64       shall not be subject to being moved to the tail of the scheduling queue
65       at  its  priority  in  the event that its original priority is changed,
66       such as by a call to sched_setparam().  Likewise, when a thread unlocks
67       a  mutex  that  has  been  initialized with the PTHREAD_PRIO_INHERIT or
68       PTHREAD_PRIO_PROTECT protocol attributes, it shall not  be  subject  to
69       being  moved to the tail of the scheduling queue at its priority in the
70       event that its original priority is changed.
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72       If a thread simultaneously owns several mutexes initialized  with  dif‐
73       ferent  protocols,  it  shall  execute at the highest of the priorities
74       that it would have obtained by each of these protocols.
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76       When a thread makes a call to pthread_mutex_lock(), the mutex was  ini‐
77       tialized    with    the    protocol    attribute   having   the   value
78       PTHREAD_PRIO_INHERIT, when the calling thread is  blocked  because  the
79       mutex  is  owned by another thread, that owner thread shall inherit the
80       priority level of the calling thread as long as it continues to own the
81       mutex.  The  implementation  shall update its execution priority to the
82       maximum of its assigned priority and all its inherited priorities. Fur‐
83       thermore, if this owner thread itself becomes blocked on another mutex,
84       the same priority inheritance effect shall be propagated to this  other
85       owner thread, in a recursive manner.
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RETURN VALUE

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

93       The pthread_mutexattr_setprotocol() function shall fail if:
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95       ENOTSUP
96              The value specified by protocol is an unsupported value.
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99       The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol()
100       functions may fail if:
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102       EINVAL The value specified by attr or protocol is invalid.
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104       EPERM  The caller does not have the privilege to perform the operation.
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107       These functions shall not return an error code of [EINTR].
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109       The following sections are informative.
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EXAMPLES

112       None.
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APPLICATION USAGE

115       None.
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RATIONALE

118       None.
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FUTURE DIRECTIONS

121       None.
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COPYRIGHT

128       Portions  of  this text are reprinted and reproduced in electronic form
129       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
130       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
131       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
132       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
133       event of any discrepancy between this version and the original IEEE and
134       The  Open Group Standard, the original IEEE and The Open Group Standard
135       is the referee document. The original Standard can be  obtained  online
136       at http://www.opengroup.org/unix/online.html .
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140IEEE/The Open Group                  2003    PTHREAD_MUTEXATTR_GETPROTOCOL(3P)