<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=utf-8"> <TITLE>"PTHREAD_BARRIER_WAIT"(P) manual page</TITLE> <META NAME="GENERATOR" CONTENT="OpenOffice.org 2.0 (Linux)"> <META NAME="CREATED" CONTENT="20050504;11484200"> <META NAME="CHANGEDBY" CONTENT="Ross Johnson"> <META NAME="CHANGED" CONTENT="20060408;9504600"> <!-- manual page source format generated by PolyglotMan v3.2, --> <!-- available at http://polyglotman.sourceforge.net/ --> </HEAD> <BODY LANG="en-GB" BGCOLOR="#ffffff" DIR="LTR"> <H4>POSIX Threads for Windows – REFERENCE - <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A></H4> <P><A HREF="index.html">Reference Index</A></P> <P><A HREF="#toc">Table of Contents</A></P> <H2><A HREF="#toc0" NAME="sect0">Name</A></H2> <P>pthread_barrier_wait - synchronize at a barrier (<B>ADVANCED REALTIME THREADS</B>) </P> <H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> <P><B>#include <pthread.h> </B> </P> <P><B>int pthread_barrier_wait(pthread_barrier_t *</B><I>barrier</I><B>); </B> </P> <H2><A HREF="#toc2" NAME="sect2">Description</A></H2> <P>The <B>pthread_barrier_wait</B> function shall synchronize participating threads at the barrier referenced by <I>barrier</I>. The calling thread shall block until the required number of threads have called <B>pthread_barrier_wait</B> specifying the barrier. </P> <P>When the required number of threads have called <B>pthread_barrier_wait</B> specifying the barrier, the constant <B>PTHREAD_BARRIER_SERIAL_THREAD</B> shall be returned to one unspecified thread and zero shall be returned to each of the remaining threads. At this point, the barrier shall be reset to the state it had as a result of the most recent <A HREF="pthread_barrier_init.html"><B>pthread_barrier_init</B>(3)</A> function that referenced it. </P> <P>The constant <B>PTHREAD_BARRIER_SERIAL_THREAD</B> is defined in <I><pthread.h></I> and its value shall be distinct from any other value returned by <B>pthread_barrier_wait</B> . </P> <P>The results are undefined if this function is called with an uninitialized barrier. </P> <P>If a signal is delivered to a thread blocked on a barrier, upon return from the signal handler the thread shall resume waiting at the barrier if the barrier wait has not completed (that is, if the required number of threads have not arrived at the barrier during the execution of the signal handler); otherwise, the thread shall continue as normal from the completed barrier wait. Until the thread in the signal handler returns from it, it is unspecified whether other threads may proceed past the barrier once they have all reached it. </P> <P>A thread that has blocked on a barrier shall not prevent any unblocked thread that is eligible to use the same processing resources from eventually making forward progress in its execution. Eligibility for processing resources shall be determined by the scheduling policy. </P> <H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2> <P>Upon successful completion, the <B>pthread_barrier_wait</B> function shall return <B>PTHREAD_BARRIER_SERIAL_THREAD</B> for a single (arbitrary) thread synchronized at the barrier and zero for each of the other threads. Otherwise, an error number shall be returned to indicate the error. </P> <H2><A HREF="#toc4" NAME="sect4">Errors</A></H2> <P>The <B>pthread_barrier_wait</B> function may fail if: </P> <DL> <DT><B>EINVAL</B> </DT><DD STYLE="margin-bottom: 0.5cm"> The value specified by <I>barrier</I> does not refer to an initialized barrier object. </DD></DL> <P> This function shall not return an error code of [EINTR]. </P> <P><I>The following sections are informative.</I> </P> <H2><A HREF="#toc5" NAME="sect5">Examples</A></H2> <P>None. </P> <H2><A HREF="#toc6" NAME="sect6">Application Usage</A></H2> <P>Applications using this function may be subject to priority inversion, as discussed in the Base Definitions volume of IEEE Std 1003.1-2001, Section 3.285, Priority Inversion. </P> <P>The <B>pthread_barrier_wait</B> function is part of the Barriers option and need not be provided on all implementations. </P> <P><B>Pthreads-w32</B> defines <B>_POSIX_BARRIERS</B> to indicate that this routine is implemented and may be used.</P> <H2><A HREF="#toc7" NAME="sect7">Rationale</A></H2> <P>None. </P> <H2><A HREF="#toc8" NAME="sect8">Future Directions</A></H2> <P>None. </P> <H2><A HREF="#toc11" NAME="sect11">Known Bugs</A></H2> <DL> <DD STYLE="margin-left: 0cm; margin-bottom: 0.5cm">In <B><SPAN LANG="en-GB">pthreads-win32</SPAN></B>, <B>pthread_barrier_wait</B> may deadlock if the number of running threads able to wait on the barrier object exceeds the value given as the <I><SPAN LANG="en-GB">count</SPAN></I> parameter in <A HREF="pthread_barrier_init.html"><B>pthread_barrier_init(3)</B></A>. </DD></DL> <H2> <A HREF="#toc9" NAME="sect9">See Also</A></H2> <P><A HREF="pthread_barrier_init.html"><B>pthread_barrier_destroy</B>(3)</A>, <A HREF="pthread_barrier_init.html"><B>pthread_barrier_init(3)</B></A>, the Base Definitions volume of IEEE Std 1003.1-2001, <I><pthread.h></I> </P> <H2><A HREF="#toc10" NAME="sect10">Copyright</A></H2> <P>Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at <A HREF="http://www.opengroup.org/unix/online.html">http://www.opengroup.org/unix/online.html</A> . </P> <P>Modified by Ross Johnson for use with <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A>.</P> <HR> <P><A NAME="toc"></A><B>Table of Contents</B></P> <UL> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Return Value</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Errors</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Examples</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect6" NAME="toc6">Application Usage</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect7" NAME="toc7">Rationale</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect8" NAME="toc8">Future Directions</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect11" NAME="toc11">Known Bugs</A> </P> <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect9" NAME="toc9">See Also</A> </P> <LI><P><A HREF="#sect10" NAME="toc10">Copyright</A> </P> </UL> </BODY> </HTML>