255 lines
7.4 KiB
HTML
255 lines
7.4 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>pthread_cancel()--Cancel Thread</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ========================================== -->
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<!-- NETMG2 SCRIPT A converted by B2H R4.1 (346) (CMS) by HOLTJM at -->
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<!-- RCHVMW2 on 29 Jan 1999 at 10:01:37 -->
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<!--File Edited November 2001 -->
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<!--End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>pthread_cancel()--Cancel Thread</h2>
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<div class="box" style="width: 50%;">
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<br>
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Syntax:
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<pre>
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#include <pthread.h>
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int pthread_cancel(pthread_t thread);
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</pre>
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Service Program Name: QP0WPTHR<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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Signal Safe: No<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>pthread_cancel</strong>() function requests cancellation of the
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target thread. The target thread is cancelled, based on its ability to be
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cancelled.</p>
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<p>When cancelability is disabled, all cancels are held pending in the target
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thread until the thread changes the cancelability. When cancelability is
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deferred, all cancels are held pending in the target thread until the thread
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changes the cancelability, calls a function that is a cancellation point, or
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calls <strong>pthread_testcancel</strong>(), thus creating a cancellation
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point. When cancelability is asynchronous, all cancels are acted upon
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immediately, interrupting the thread with its processing.</p>
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<p><strong>Note:</strong> You should not use asynchronous thread cancellation
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through the <strong>PTHREAD_CANCEL_ASYNCHRONOUS</strong> option of
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<strong>pthread_setcanceltype</strong>() in your application. See the common
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user errors section of this document for more information.</p>
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<p>The following functions are cancellation points:</p>
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<ul>
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<li>pthread_cond_timedwait()</li>
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<li>pthread_cond_wait()</li>
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<li>pthread_delay_np()</li>
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<li>pthread_join()</li>
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<li>pthread_join_np()</li>
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<li>pthread_extendedjoin_np()</li>
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<li>pthread_testcancel()</li>
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</ul>
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<p>After action is taken for the target thread to be cancelled, the following
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events occur in that thread.</p>
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<ol>
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<li>The thread calls cancellation cleanup handlers with cancellation disabled
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until the last cancellation cleanup handler returns. The handlers are called in
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Last In, First Out (LIFO) order.</li>
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<li>Data destructors are called for any thread-specific data entries that have
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a non NULL value for both the value and the destructor.</li>
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<li>When the last cancellation cleanup handler returns, the thread is
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terminated and a status of <strong>PTHREAD_CANCELED</strong> is made available
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to any threads joining the target.</li>
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<li>Any mutexes that are held by a thread that terminates, are abandoned and
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are no longer valid. Subsequent calls by other threads that attempt to acquire
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the abandoned mutex (<strong>pthread_mutex_lock</strong>() or
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<strong>pthread_mutex_trylock</strong>()) fail with an
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<strong>EOWNERTERM</strong> error.</li>
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<li>Application visible process resources are not released. This includes but
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is not limited to mutexes, file descriptors, or any process level cleanup
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actions.</li>
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</ol>
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<p>A cancellation cleanup handler should not exit by <strong>longjmp()</strong>
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or <strong>siglongjmp()</strong>.</p>
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<p>In the i5/OS implementation of threads, the initial thread is special.
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Termination of the initial thread by <strong>pthread_exit</strong>(),
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<strong>pthread_cancel</strong>() or any other thread termination mechanism
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terminates the entire process.</p>
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<br>
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<h3>Authorities and Locks</h3>
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<p>None.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>thread</strong></dt>
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<dd>(Input) Pthread handle to the target thread</dd>
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</dl>
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<br>
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<h3>Return Value</h3>
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<dl>
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<dt><strong>0</strong></dt>
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<dd><strong>pthread_cancel</strong>() was successful.<br><br></dd>
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<dt><strong>value</strong></dt>
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<dd><strong>pthread_cancel</strong>() was not successful. <em>value</em> is set
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to indicate the error condition.</dd>
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</dl>
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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>pthread_cancel</strong>() was not successful, the error condition
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returned usually indicates one of the following errors. Under some conditions,
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the value returned could indicate an error other than those listed here.</p>
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<dl>
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<dt><em>[EINVAL]</em></dt>
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<dd><p>The value specified for the argument is not correct. <a name=
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"294434"></a></p></dd>
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<dt><em>[ESRCH]</em></dt>
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<dd><p>No thread could be found that matched the thread ID specified.</p></dd>
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</dl>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li>The <<strong>pthread.h</strong>> header file. See <a href=
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"rzah4hed.htm">Header files for Pthread functions</a>.<br><br></li>
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<li><a href="users_41.htm">pthread_cleanup_pop()</a>--Pop Cleanup Handler off of
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Cancellation Cleanup Stack<br><br></li>
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<li><a href="users_42.htm">pthread_cleanup_push()</a>--Push Cleanup Handler onto
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Cancellation Cleanup Stack<br><br></li>
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<li><a href="users_18.htm">pthread_exit()</a>--Terminate Calling Thread<br><br></li>
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<li><a href="users_44.htm">pthread_setcancelstate()</a>--Set Cancel State<br><br></li>
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<li><a href="users_45.htm">pthread_setcanceltype()</a>--Set Cancel Type</li>
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</ul>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<pre>
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#include <pthread.h>
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#include <stdio.h>
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#include "check.h"
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void *threadfunc(void *parm)
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{
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printf("Entered secondary thread\n");
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while (1) {
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printf("Secondary thread is looping\n");
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pthread_testcancel();
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sleep(1);
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}
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return NULL;
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}
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int main(int argc, char **argv)
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{
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pthread_t thread;
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int rc=0;
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printf("Entering testcase\n");
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/* Create a thread using default attributes */
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printf("Create thread using the NULL attributes\n");
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rc = pthread_create(&thread, NULL, threadfunc, NULL);
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checkResults("pthread_create(NULL)\n", rc);
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/* sleep() is not a very robust way to wait for the thread */
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sleep(2);
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printf("Cancel the thread\n");
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rc = pthread_cancel(thread);
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checkResults("pthread_cancel()\n", rc);
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/* sleep() is not a very robust way to wait for the thread */
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sleep(3);
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printf("Main completed\n");
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return 0;
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}
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</pre>
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<p><strong>Output:</strong></p>
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<pre>
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Entering testcase
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Create thread using the NULL attributes
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Entered secondary thread
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Secondary thread is looping
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Secondary thread is looping
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Cancel the thread
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Main completed
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</pre>
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<br>
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<hr>API introduced: V4R3
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"rzah4mst.htm">Pthread APIs</a> | <a href="aplist.htm">APIs by
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category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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