303 lines
10 KiB
HTML
303 lines
10 KiB
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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_sigmask()--Set or Get Signal Mask</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_sigmask()--Set or Get Signal Mask</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> #include <pthread.h>
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#include <signal.h>
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int pthread_sigmask(int how, const sigset_t *set,
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sigset_t *oset);</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>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>pthread_sigmask</strong>() function examines or modifies the signal blocking mask for the current thread.</p>
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<p>The signals <strong>SIGKILL</strong> or <strong>SIGStop</strong> cannot be blocked. Any attempt to use <strong>pthread_sigmask</strong>() to block these signals is simply ignored, and no error is returned.</p>
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<p><strong>SIGFPE</strong>, <strong>SIGILL</strong>, and <strong>SIGSEGV</strong> signals that are not artificially generated by <strong>kill</strong>(), <strong>pthread_kill</strong>() or <strong>raise</strong>() (that is, were generated by the system as a result of a hardware or software exception) are not blocked.</p>
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<p>If there are any pending unblocked signals after <strong>pthread_sigmask</strong>() has changed the signal mask, at least one of those signals is delivered to the process before <strong>pthread_sigmask</strong>() returns.</p>
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<p>If <strong>pthread_sigmask</strong>() fails, the signal mask of the thread is not changed.</p>
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<p>The possible values for <em>how</em>, which are defined in the <strong><signal.h></strong> header file, are as follows:</p>
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<dl>
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<dt><strong>SIG_BLOCK</strong></dt>
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<dd><p>Indicates that the set of signals given by <em>set</em> should be blocked, in addition to the set currently being blocked</p></dd>
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<dt><strong>SIG_UNBLOCK</strong></dt>
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<dd><p>Indicates that the set of signals given by <em>set</em> should not be blocked. These signals are removed from the current set
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of signals being blocked</p></dd>
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<dt><strong>SIG_SETMASK</strong></dt>
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<dd><p>Indicates that the set of signals given by <em>set</em> should replace the old set of signals being blocked</p></dd>
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</dl>
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<p>The <em>set</em> parameter points to a signal set that contains the new signals that should be blocked or unblocked (depending on the value of <em>how</em>), or it points to the new signal mask if the value of <em>how</em> is <strong>SIG_SETMASK</strong>. If <em>set</em> is a <strong>NULL</strong> pointer, the set of blocked signals is not changed. If <em>set</em> is <strong>NULL</strong>, the value of <em>how</em> is ignored.</p>
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<p>The signal set manipulation functions (<strong>sigemptyset</strong>(), <strong>sigfillset</strong>(), <strong>sigaddset</strong>(), and <strong>sigdelset</strong>()) must be used to establish the new signal set pointed to by <em>set</em>.</p>
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<p>The <strong>pthread_sigmask</strong>() function determines the current signal set and returns this information in *<em>oset</em>. If <em>set</em> is <strong>NULL</strong>, <em>oset</em> returns the current set of signals being blocked. When <em>set</em> is not <strong>NULL</strong>, the set of signals pointed to by <em>oset</em> is the previous set.</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>how</strong></dt>
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<dd>(Input) The way in which the signal set is changed</dd>
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<dt><strong>set</strong></dt>
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<dd>(Input) A pointer to a set of signals to be used to change the currently blocked set. This value can be NULL</dd>
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<dt><strong>oset</strong></dt>
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<dd>(Output) A pointer to the space where the previous signal mask is stored. This value can be NULL</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_sigmask</strong>() was successful.</dd>
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<dt><strong>value</strong></dt>
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<dd><strong>pthread_sigmask</strong>() was not successful. <em>value</em> 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_sigmask</strong>() was not successful, the error condition returned usually indicates one of the following errors. Under some conditions, 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.</p></dd>
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<dt><em>[ENOTSIGINIT]</em></dt>
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<dd><p>The process is not enabled for signals.</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="rzah4hed.htm">Header files for Pthread functions</a>.<br><br></li>
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<li>
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<a href="users_95.htm">pthread_kill()</a>--Send Signal to Thread<br><br></li>
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<li>
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<a href="users_97.htm">pthread_signal_to_cancel_np()</a>--Convert Signals to Cancel Requests</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>#define _MULTI_THREADED
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#include <pthread.h>
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#include <stdio.h>
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#include <signal.h>
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#include "check.h"
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#define NUMTHREADS 3
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void sighand(int signo);
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void *threadfunc(void *parm)
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{
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pthread_t self = pthread_self();
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pthread_id_np_t tid;
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int rc;
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pthread_getunique_np(&self, &tid);
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printf("Thread 0x%.8x %.8x entered\n", tid);
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errno = 0;
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rc = sleep(30);
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if (rc != 0 && errno == EINTR) {
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printf("Thread 0x%.8x %.8x got a signal delivered to it\n",
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tid);
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return NULL;
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}
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printf("Thread 0x%.8x %.8x did not get expected results! rc=%d, errno=%d\n",
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tid, rc, errno);
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return NULL;
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}
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void *threadmasked(void *parm)
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{
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pthread_t self = pthread_self();
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pthread_id_np_t tid;
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sigset_t mask;
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int rc;
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pthread_getunique_np(&self, &tid);
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printf("Masked thread 0x%.8x %.8x entered\n", tid);
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sigfillset(&mask); /* Mask all allowed signals */
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rc = pthread_sigmask(SIG_BLOCK, &mask, NULL);
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checkResults("pthread_sigmask()\n", rc);
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errno = 0;
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rc = sleep(15);
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if (rc != 0) {
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printf("Masked thread 0x%.8x %.8x did not get expected results! "
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"rc=%d, errno=%d\n",
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tid, rc, errno);
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return NULL;
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}
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printf("Masked thread 0x%.8x %.8x completed masked work\n",
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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;
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int i;
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struct sigaction actions;
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pthread_t threads[NUMTHREADS];
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pthread_t maskedthreads[NUMTHREADS];
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printf("Enter Testcase - %s\n", argv[0]);
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printf("Set up the alarm handler for the process\n");
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memset(&actions, 0, sizeof(actions));
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sigemptyset(&actions.sa_mask);
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actions.sa_flags = 0;
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actions.sa_handler = sighand;
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rc = sigaction(SIGALRM,&actions,NULL);
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checkResults("sigaction\n", rc);
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printf("Create masked and unmasked threads\n");
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for(i=0; i<NUMTHREADS; ++i) {
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rc = pthread_create(&threads[i], NULL, threadfunc, NULL);
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checkResults("pthread_create()\n", rc);
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rc = pthread_create(&maskedthreads[i], NULL, threadmasked, NULL);
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checkResults("pthread_create()\n", rc);
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}
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sleep(3);
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printf("Send a signal to masked and unmasked threads\n");
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for(i=0; i<NUMTHREADS; ++i) {
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rc = pthread_kill(threads[i], SIGALRM);
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checkResults("pthread_kill()\n", rc);
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rc = pthread_kill(maskedthreads[i], SIGALRM);
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checkResults("pthread_kill()\n", rc);
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}
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printf("Wait for masked and unmasked threads to complete\n");
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for(i=0; i<NUMTHREADS; ++i) {
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rc = pthread_join(threads[i], NULL);
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checkResults("pthread_join()\n", rc);
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rc = pthread_join(maskedthreads[i], NULL);
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checkResults("pthread_join()\n", rc);
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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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void sighand(int signo)
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{
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pthread_t self = pthread_self();
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pthread_id_np_t tid;
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pthread_getunique_np(&self, &tid);
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printf("Thread 0x%.8x %.8x in signal handler\n",
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tid);
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return;
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}</pre>
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<p><strong>Output:</strong></p>
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<pre>Thread 0x00000000 0000000d entered
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Masked thread 0x00000000 0000000a entered
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Thread 0x00000000 00000009 entered
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Thread 0x00000000 0000000b entered
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Masked thread 0x00000000 0000000e entered
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Masked thread 0x00000000 0000000c entered
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Send a signal to masked and unmasked threads
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Wait for masked and unmasked threads to complete
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Thread 0x00000000 00000009 in signal handler
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Thread 0x00000000 00000009 got a signal delivered to it
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Thread 0x00000000 0000000b in signal handler
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Thread 0x00000000 0000000b got a signal delivered to it
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Thread 0x00000000 0000000d in signal handler
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Thread 0x00000000 0000000d got a signal delivered to it
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Masked thread 0x00000000 0000000a completed masked work
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Masked thread 0x00000000 0000000e completed masked work
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Masked thread 0x00000000 0000000c completed masked work
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Main completed</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> |
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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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