274 lines
8.1 KiB
HTML
274 lines
8.1 KiB
HTML
<!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_setcanceltype()--Set Cancel Type</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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<!-- Begin Header Records ========================================== -->
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<!--File Edited November 2001 --><!--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_setcanceltype()--Set Cancel Type</h2>
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<div class="box" style="width: 60%;">
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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_setcanceltype(int type, int *oldtype);
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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: Yes<br><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_setcanceltype</strong>() function sets the cancel <em>
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type</em> to one of <strong>PTHREAD_CANCEL_DEFERRED</strong> or <strong>
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PTHREAD_CANCEL_ASYNCHRONOUS</strong> and returns the old cancel type into the
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location specified by <em>oldtype</em> (if <em>oldtype</em> is
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non-<strong>NULL</strong>)</p>
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<p>Cancelability consists of 3 separate states (disabled, deferred,
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asynchronous) that can be represented by 2 boolean values.</p>
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<table border width="80%">
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<tr>
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<th valign="top">Cancelability</th>
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<th valign="top">Cancelability State</th>
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<th valign="top">Cancelability Type</th>
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</tr>
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<tr>
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<td align="left" valign="top" width="20%">disabled</td>
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<td align="left" valign="top" width="40%"><strong>
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PTHREAD_CANCEL_DISABLE</strong></td>
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<td align="left" valign="top" width="40%"><strong>
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PTHREAD_CANCEL_DEFERRED</strong></td>
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</tr>
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<tr>
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<td align="left" valign="top">disabled</td>
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<td align="left" valign="top"><strong>PTHREAD_CANCEL_DISABLE</strong></td>
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<td align="left" valign="top"><strong>PTHREAD_CANCEL_ASYNCHRONOUS</strong></td>
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</tr>
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<tr>
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<td align="left" valign="top">deferred</td>
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<td align="left" valign="top"><strong>PTHREAD_CANCEL_ENABLE</strong></td>
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<td align="left" valign="top"><strong>PTHREAD_CANCEL_DEFERRED</strong></td>
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</tr>
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<tr>
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<td align="left" valign="top">asynchronous</td>
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<td align="left" valign="top"><strong>PTHREAD_CANCEL_ENABLE</strong></td>
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<td align="left" valign="top"><strong>PTHREAD_CANCEL_ASYNCHRONOUS</strong></td>
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</tr>
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</table>
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<p>The default cancelability state is deferred.</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 which 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> It is recommended that your application not use
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asynchronous thread cancellation through the <strong>
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PTHREAD_CANCEL_ASYNCHRONOUS</strong> option of <strong>
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pthread_setcanceltype</strong>(). See the common user errors section of this
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document for more information.</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>type</strong></dt>
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<dd>(Input) New cancel type (one of <strong>PTHREAD_CANCEL_DEFERRED</strong> or
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<strong>PTHREAD_CANCEL_ASYNCHRONOUS</strong>) <a name="294773"></a></dd>
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<dt><strong>oldtype</strong></dt>
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<dd>(Output) Address of variable to contain old cancel type.
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(<strong>NULL</strong> is allowed)</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_setcanceltype</strong>() was successful.</dd>
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<dt><strong>value</strong></dt>
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<dd><strong>pthread_setcanceltype</strong>() was not successful. <em>value</em>
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is set 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_setcanceltype</strong>() was not successful, the error
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condition returned usually indicates one of the following errors. Under some
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conditions, the value returned could indicate an error other than those listed
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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.</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_39.htm">pthread_cancel()</a>--Cancel Thread<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_46.htm">pthread_testcancel()</a>--Create Cancellation
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Point</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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#define _MULTI_THREADED
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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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pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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void cleanupHandler(void *parm)
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{
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int rc;
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printf("Inside cleanup handler, unlock mutex\n");
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rc = pthread_mutex_unlock((pthread_mutex_t *)parm);
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checkResults("pthread_mutex_unlock\n", rc);
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}
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void *threadfunc(void *parm)
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{
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int rc;
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int oldtype;
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printf("Entered secondary thread, lock mutex\n");
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rc = pthread_mutex_lock(&mutex);
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checkResults("pthread_mutex_lock()\n", rc);
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pthread_cleanup_push(cleanupHandler, &mutex);
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/* We must assume there is a good reason for async. cancellability */
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/* and also, we must assume that if we get interrupted, it is */
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/* appropriate to unlock the mutex. More than likely it is not */
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/* because we will have left some data structures in a strange state */
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/* if we are async. interrupted while holding the mutex */
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rc = pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &oldtype);
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checkResults("pthread_setcanceltype()\n", rc);
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printf("Secondary thread is now looping\n");
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while (1) { sleep(1); }
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printf("Unexpectedly got out of loop!\n");
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pthread_cleanup_pop(0);
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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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void *status;
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printf("Enter Testcase - %s\n", argv[0]);
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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(1);
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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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rc = pthread_join(thread, &status);
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if (status != PTHREAD_CANCELED) {
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printf("Unexpected thread status\n");
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exit(1);
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}
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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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Enter Testcase - QP0WTEST/TPSETCANT0
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Create thread using the NULL attributes
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Entered secondary thread, lock mutex
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Secondary thread is now looping
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Cancel the thread
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Inside cleanup handler, unlock mutex
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Main completed
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</pre>
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<hr>
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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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