98 lines
3.3 KiB
HTML
98 lines
3.3 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>Threads do not necessarily start before pthread_create() returns</title>
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<!-- Begin Header Records ========================================== -->
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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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<!-- Change History: -->
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<!-- YYMMDD USERID Change description -->
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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>Threads do not necessarily start before pthread_create() returns</h2>
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<p>A thread may or may not start running before the return from <strong>
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pthread_create</strong>(). Depending on the amount of time left in the creating
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threads, time slice, and the other activity on the system, the creating thread
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may return before the new thread runs.</p>
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<p>The thread implementations of some systems guarantee a certain ordered
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behavior for thread creation versus the execution of the first statement in the
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new thread. On the iSeries, it is unknown which happens first, the execution of
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the first instruction in the new thread or the return from <strong>
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pthread_create</strong>().</p>
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<p>The following example shows an incorrectly written application.</p>
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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_t thread
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void *threadfunc(void *parm)
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{
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pthread_id_np_t tid;
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#error "This is an ERROR."
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#error "The 'thread' variable is shared between threads"
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#error "and must be protected by a mutex."
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pthread_getunique_np(&thread, &tid);
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printf("Thread 0x%.8x %.8x started\n", tid);
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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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int rc=0;
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printf("Enter Testcase - %s\n", argv[0]);
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#error "This is an ERROR."
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#error "The order of thread thread startup, and return from"
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#error "the pthread_create() API is NOT deterministic."
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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() isn't a very robust way to wait for the thread */
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sleep(5);
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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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<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">
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<a href="#Top_Of_Page">Top</a> |
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<a href="rzah4mst.htm">Pthread APIs</a> |
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<a href="aplist.htm">APIs by 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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