152 lines
6.3 KiB
HTML
152 lines
6.3 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>pthread_cancel</title>
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<basefont size="3"> <a name="pthread_cancel"></a> <a name="tag_03_513"></a><!-- pthread_cancel -->
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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_513_01"></a>NAME</h4>
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<blockquote>pthread_cancel - cancel execution of a thread</blockquote>
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<h4><a name="tag_03_513_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')">THR</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_cancel(pthread_t</tt> <i>thread</i><tt>); <img src="../images/opt-end.gif" alt="[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_513_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>pthread_cancel</i>() function shall request that <i>thread</i> be canceled. The target thread's cancelability state and
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type determines when the cancelation takes effect. When the cancelation is acted on, the cancelation cleanup handlers for
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<i>thread</i> shall be called. When the last cancelation cleanup handler returns, the thread-specific data destructor functions
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shall be called for <i>thread</i>. When the last destructor function returns, <i>thread</i> shall be terminated.</p>
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<p>The cancelation processing in the target thread shall run asynchronously with respect to the calling thread returning from
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<i>pthread_cancel</i>().</p>
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</blockquote>
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<h4><a name="tag_03_513_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>If successful, the <i>pthread_cancel</i>() function shall return zero; otherwise, an error number shall be returned to indicate
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the error.</p>
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</blockquote>
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<h4><a name="tag_03_513_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>pthread_cancel</i>() function may fail if:</p>
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<dl compact>
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<dt>[ESRCH]</dt>
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<dd>No thread could be found corresponding to that specified by the given thread ID.</dd>
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</dl>
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<p>The <i>pthread_cancel</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_513_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_513_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_513_08"></a>RATIONALE</h4>
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<blockquote>
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<p>Two alternative functions were considered for sending the cancelation notification to a thread. One would be to define a new
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SIGCANCEL signal that had the cancelation semantics when delivered; the other was to define the new <i>pthread_cancel</i>()
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function, which would trigger the cancelation semantics.</p>
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<p>The advantage of a new signal was that so much of the delivery criteria were identical to that used when trying to deliver a
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signal that making cancelation notification a signal was seen as consistent. Indeed, many implementations implement cancelation
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using a special signal. On the other hand, there would be no signal functions that could be used with this signal except <a href=
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"../functions/pthread_kill.html"><i>pthread_kill</i>()</a>, and the behavior of the delivered cancelation signal would be unlike
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any previously existing defined signal.</p>
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<p>The benefits of a special function include the recognition that this signal would be defined because of the similar delivery
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criteria and that this is the only common behavior between a cancelation request and a signal. In addition, the cancelation
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delivery mechanism does not have to be implemented as a signal. There are also strong, if not stronger, parallels with language
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exception mechanisms than with signals that are potentially obscured if the delivery mechanism is visibly closer to signals.</p>
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<p>In the end, it was considered that as there were so many exceptions to the use of the new signal with existing signals functions
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it would be misleading. A special function has resolved this problem. This function was carefully defined so that an implementation
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wishing to provide the cancelation functions on top of signals could do so. The special function also means that implementations
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are not obliged to implement cancelation with signals.</p>
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</blockquote>
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<h4><a name="tag_03_513_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_513_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="pthread_exit.html"><i>pthread_exit</i>()</a> , <a href=
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"pthread_cond_timedwait.html"><i>pthread_cond_timedwait</i>()</a> , <a href="pthread_join.html"><i>pthread_join</i>()</a> , <a
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href="pthread_setcancelstate.html"><i>pthread_setcancelstate</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_513_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with the POSIX Threads Extension.</p>
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</blockquote>
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<h4><a name="tag_03_513_12"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>pthread_cancel</i>() function is marked as part of the Threads option.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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