151 lines
5.7 KiB
HTML
151 lines
5.7 KiB
HTML
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<title>pthread_setschedprio</title>
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<basefont size="3"> <a name="pthread_setschedprio"></a> <a name="tag_03_571"></a><!-- pthread_setschedprio -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_571_01"></a>NAME</h4>
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<blockquote>pthread_setschedprio - dynamic thread scheduling parameters access (<b>REALTIME THREADS</b>)</blockquote>
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<h4><a name="tag_03_571_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('THR TPS')">THR TPS</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/pthread.h.html">pthread.h</a>><br>
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<br>
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int pthread_setschedprio(pthread_t</tt> <i>thread</i><tt>, int</tt> <i>prio</i><tt>); <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_571_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>pthread_setschedprio</i>() function shall set the scheduling priority for the thread whose thread ID is given by
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<i>thread</i> to the value given by <i>prio</i>. See <a href="xsh_chap02_08.html#tag_02_08_04_01"><i>Scheduling Policies</i></a>
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for a description on how this function call affects the ordering of the thread in the thread list for its new priority.</p>
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<p>If the <i>pthread_setschedprio</i>() function fails, the scheduling priority of the target thread shall not be changed.</p>
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</blockquote>
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<h4><a name="tag_03_571_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>If successful, the <i>pthread_setschedprio</i>() function shall return zero; otherwise, an error number shall be returned to
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indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_571_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>pthread_setschedprio</i>() function may fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The value of <i>prio</i> is invalid for the scheduling policy of the specified thread.</dd>
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<dt>[ENOTSUP]</dt>
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<dd>An attempt was made to set the priority to an unsupported value.</dd>
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<dt>[EPERM]</dt>
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<dd>The caller does not have the appropriate permission to set the scheduling policy of the specified thread.</dd>
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<dt>[EPERM]</dt>
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<dd>The implementation does not allow the application to modify the priority to the value specified.</dd>
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<dt>[ESRCH]</dt>
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<dd>The value specified by <i>thread</i> does not refer to an existing thread.</dd>
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</dl>
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<p>The <i>pthread_setschedprio</i>() function shall not return an error code of [EINTR].</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_571_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_571_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_571_08"></a>RATIONALE</h4>
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<blockquote>
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<p>The <i>pthread_setschedprio</i>() function provides a way for an application to temporarily raise its priority and then lower it
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again, without having the undesired side effect of yielding to other threads of the same priority. This is necessary if the
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application is to implement its own strategies for bounding priority inversion, such as priority inheritance or priority ceilings.
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This capability is especially important if the implementation does not support the Thread Priority Protection or Thread Priority
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Inheritance options, but even if those options are supported it is needed if the application is to bound priority inheritance for
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other resources, such as semaphores.</p>
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<p>The standard developers considered that while it might be preferable conceptually to solve this problem by modifying the
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specification of <a href="../functions/pthread_setschedparam.html"><i>pthread_setschedparam</i>()</a>, it was too late to make such
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a change, as there may be implementations that would need to be changed. Therefore, this new function was introduced.</p>
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</blockquote>
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<h4><a name="tag_03_571_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_571_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="xsh_chap02_08.html#tag_02_08_04_01"><i>Scheduling Policies</i></a> , <a href=
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"pthread_getschedparam.html"><i>pthread_getschedparam</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a
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href="../basedefs/pthread.h.html"><i><pthread.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_571_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Included as a response to IEEE PASC Interpretation 1003.1 #96.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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