150 lines
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150 lines
6.0 KiB
HTML
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<title>pthread_barrier_wait</title>
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<basefont size="3"> <a name="pthread_barrier_wait"></a> <a name="tag_03_508"></a><!-- pthread_barrier_wait -->
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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_508_01"></a>NAME</h4>
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<blockquote>pthread_barrier_wait - synchronize at a barrier (<b>ADVANCED REALTIME THREADS</b>)</blockquote>
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<h4><a name="tag_03_508_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 BAR')">THR BAR</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_barrier_wait(pthread_barrier_t *</tt><i>barrier</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border=
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"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_508_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>pthread_barrier_wait</i>() function shall synchronize participating threads at the barrier referenced by <i>barrier</i>.
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The calling thread shall block until the required number of threads have called <i>pthread_barrier_wait</i>() specifying the
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barrier.</p>
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<p>When the required number of threads have called <i>pthread_barrier_wait</i>() specifying the barrier, the constant
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PTHREAD_BARRIER_SERIAL_THREAD shall be returned to one unspecified thread and zero shall be returned to each of the remaining
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threads. At this point, the barrier shall be reset to the state it had as a result of the most recent <a href=
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"../functions/pthread_barrier_init.html"><i>pthread_barrier_init</i>()</a> function that referenced it.</p>
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<p>The constant PTHREAD_BARRIER_SERIAL_THREAD is defined in <a href="../basedefs/pthread.h.html"><i><pthread.h></i></a> and
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its value shall be distinct from any other value returned by <i>pthread_barrier_wait</i>().</p>
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<p>The results are undefined if this function is called with an uninitialized barrier.</p>
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<p>If a signal is delivered to a thread blocked on a barrier, upon return from the signal handler the thread shall resume waiting
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at the barrier if the barrier wait has not completed (that is, if the required number of threads have not arrived at the barrier
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during the execution of the signal handler); otherwise, the thread shall continue as normal from the completed barrier wait. Until
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the thread in the signal handler returns from it, it is unspecified whether other threads may proceed past the barrier once they
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have all reached it.</p>
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<p>A thread that has blocked on a barrier shall not prevent any unblocked thread that is eligible to use the same processing
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resources from eventually making forward progress in its execution. Eligibility for processing resources shall be determined by the
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scheduling policy.</p>
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</blockquote>
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<h4><a name="tag_03_508_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, the <i>pthread_barrier_wait</i>() function shall return PTHREAD_BARRIER_SERIAL_THREAD for a single
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(arbitrary) thread synchronized at the barrier and zero for each of the other threads. Otherwise, an error number shall be returned
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to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_508_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>pthread_barrier_wait</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 specified by <i>barrier</i> does not refer to an initialized barrier object.</dd>
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</dl>
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<p>This 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_508_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_508_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Applications using this function may be subject to priority inversion, as discussed in the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap03.html#tag_03_285">Section 3.285, Priority Inversion</a>.</p>
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<p>The <i>pthread_barrier_wait</i>() function is part of the Barriers option and need not be provided on all implementations.</p>
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</blockquote>
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<h4><a name="tag_03_508_08"></a>RATIONALE</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_508_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_508_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="pthread_barrier_destroy.html"><i>pthread_barrier_destroy</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a 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_508_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from IEEE Std 1003.1j-2000.</p>
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<p>In the SYNOPSIS, the inclusion of <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> is no longer
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required.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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