206 lines
5.9 KiB
HTML
206 lines
5.9 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_testcancel()--Create Cancellation Point</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_testcancel()--Create Cancellation Point</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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void pthread_testcancel(void);
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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_testcancel</strong>() function creates a cancellation
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point in the calling thread. If cancelability is currently disabled, this
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function has no effect. For more information on cancelability, see <a href=
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"users_38.htm">Thread cancellation APIs</a>.</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 <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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<p>None.</p>
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<br>
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<h3>Return Value</h3>
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<p>None.</p>
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<br>
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<h3>Error Conditions</h3>
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<p>None.</p>
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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_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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#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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void cleanupHandler(void *parm) {
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printf("Inside cancellation cleanup handler\n");
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}
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void *threadfunc(void *parm)
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{
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unsigned int i=0;
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int rc=0, oldState=0;
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printf("Entered secondary thread\n");
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pthread_cleanup_push(cleanupHandler, NULL);
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rc = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldState);
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checkResults("pthread_setcancelstate()\n", rc);
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/* Allow cancel to be pending on this thread */
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sleep(2);
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while (1) {
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printf("Secondary thread is now looping\n");
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++i;
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sleep(1);
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/* pthread_testcancel() has no effect until cancelability is enabled.*/
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/* At that time, a call to pthread_testcancel() should result in the */
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/* pending cancel being acted upon */
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pthread_testcancel();
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if (i == 5) {
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printf("Cancel state set to ENABLE\n");
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rc = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,&oldState);
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checkResults("pthread_setcancelstate(2)\n", rc);
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/* Now, cancellation points will allow pending cancels
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to get through to this thread */
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}
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} /* infinite */
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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=NULL;
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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(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("Thread returned unexpected result!\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/TPTESTC0
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Create thread using the NULL attributes
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Entered secondary thread
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Cancel the thread
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Secondary thread is now looping
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Secondary thread is now looping
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Secondary thread is now looping
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Secondary thread is now looping
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Secondary thread is now looping
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Cancel state set to ENABLE
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Secondary thread is now looping
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Inside cancellation cleanup handler
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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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