<!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_RWLOCK_DESTROY"(P) manual page</TITLE> <META NAME="GENERATOR" CONTENT="OpenOffice.org 1.1.3 (Linux)"> <META NAME="CREATED" CONTENT="20050505;10211800"> <META NAME="CHANGED" CONTENT="20050505;18563400"> <!-- 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_rwlock_destroy, pthread_rwlock_init - destroy and initialize a read-write lock object </P> <H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> <P><B>#include <pthread.h> </B> </P> <P><B>pthread_wrlock_t </B><I>rwlock</I> <B>= PTHREAD_RWLOCK_INITIALIZER;</B></P> <P><B>int pthread_rwlock_destroy(pthread_rwlock_t *</B><I>rwlock</I><B>); <BR>int pthread_rwlock_init(pthread_rwlock_t *restrict</B> <I>rwlock</I><B>, const pthread_rwlockattr_t *restrict</B> <I>attr</I><B>); </B> </P> <H2><A HREF="#toc2" NAME="sect2">Description</A></H2> <P>The <B>pthread_rwlock_destroy</B> function shall destroy the read-write lock object referenced by <I>rwlock</I> and release any resources used by the lock. The effect of subsequent use of the lock is undefined until the lock is reinitialized by another call to <B>pthread_rwlock_init</B>. An implementation may cause <B>pthread_rwlock_destroy</B> to set the object referenced by <I>rwlock</I> to an invalid value. Results are undefined if <B>pthread_rwlock_destroy</B> is called when any thread holds <I>rwlock</I>. Attempting to destroy an uninitialized read-write lock results in undefined behavior. </P> <P>The <B>pthread_rwlock_init</B> function shall allocate any resources required to use the read-write lock referenced by <I>rwlock</I> and initializes the lock to an unlocked state with attributes referenced by <I>attr</I>. If <I>attr</I> is NULL, the default read-write lock attributes shall be used; the effect is the same as passing the address of a default read-write lock attributes object. Once initialized, the lock can be used any number of times without being reinitialized. Results are undefined if <B>pthread_rwlock_init</B> is called specifying an already initialized read-write lock. Results are undefined if a read-write lock is used without first being initialized. </P> <P>If the <B>pthread_rwlock_init</B> function fails, <I>rwlock</I> shall not be initialized and the contents of <I>rwlock</I> are undefined. </P> <P><B>Pthreads-w32</B> supports statically initialized <I>rwlock</I> objects using <B>PTHREAD_RWLOCK_INITIALIZER</B>. <SPAN STYLE="font-weight: medium"> An application should still call <B>pthread_rwlock_destroy</B> at some point to ensure that any resources consumed by the read/write lock are released.</SPAN></P> <P>Only the object referenced by <I>rwlock</I> may be used for performing synchronization. The result of referring to copies of that object in calls to <B>pthread_rwlock_destroy</B> , <B>pthread_rwlock_rdlock</B> , <B>pthread_rwlock_timedrdlock</B> , <B>pthread_rwlock_timedwrlock</B> , <B>pthread_rwlock_tryrdlock</B> , <B>pthread_rwlock_trywrlock</B> , <B>pthread_rwlock_unlock</B> , or <B>pthread_rwlock_wrlock</B> is undefined. </P> <P><B>Pthreads-w32</B> defines <B>_POSIX_READER_WRITER_LOCKS</B> in pthread.h as 200112L to indicate that the reader/writer routines are implemented and may be used.</P> <H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2> <P>If successful, the <B>pthread_rwlock_destroy</B> and <B>pthread_rwlock_init</B> functions shall return zero; otherwise, an error number shall be returned to indicate the error. </P> <P>The [EBUSY] and [EINVAL] error checks, if implemented, act as if they were performed immediately at the beginning of processing for the function and caused an error return prior to modifying the state of the read-write lock specified by <I>rwlock</I>. </P> <H2><A HREF="#toc4" NAME="sect4">Errors</A></H2> <P>The <B>pthread_rwlock_destroy</B> function may fail if: </P> <DL> <DT><B>EBUSY</B> </DT><DD> The implementation has detected an attempt to destroy the object referenced by <I>rwlock</I> while it is locked. </DD><DT> <B>EINVAL</B> </DT><DD STYLE="margin-bottom: 0.5cm"> The value specified by <I>rwlock</I> is invalid. </DD></DL> <P> The <B>pthread_rwlock_init</B> function shall fail if: </P> <DL> <DT><B>EAGAIN</B> </DT><DD> The system lacked the necessary resources (other than memory) to initialize another read-write lock. </DD><DT> <B>ENOMEM</B> </DT><DD> Insufficient memory exists to initialize the read-write lock. </DD><DD STYLE="margin-left: 0cm; margin-bottom: 0.5cm"> <BR><BR> </DD></DL> <P> The <B>pthread_rwlock_init</B> function may fail if: </P> <DL> <DT><B>EINVAL</B> </DT><DD STYLE="margin-bottom: 0.5cm"> The value specified by <I>attr</I> is invalid. </DD></DL> <P> These functions 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 these and related read-write lock functions 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> <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="#toc9" NAME="sect9">See Also</A></H2> <P><A HREF="pthread_rwlock_rdlock.html"><B>pthread_rwlock_rdlock</B>(3)</A> <B>,</B> <A HREF="pthread_rwlock_timedrdlock.html"><B>pthread_rwlock_timedrdlock</B>(3)</A> <B>,</B> <A HREF="pthread_rwlock_timedwrlock.html"><B>pthread_rwlock_timedwrlock</B>(3)</A> <B>,</B> <A HREF="pthread_rwlock_rdlock.html"><B>pthread_rwlock_tryrdlock</B>(3)</A> <B>,</B> <A HREF="pthread_rwlock_wrlock.html"><B>pthread_rwlock_trywrlock</B>(3)</A> <B>,</B> <A HREF="pthread_rwlock_unlock.html"><B>pthread_rwlock_unlock</B>(3)</A> <B>,</B> <A HREF="pthread_rwlock_wrlock.html"><B>pthread_rwlock_wrlock</B>(3)</A> <B>,</B> 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="#sect9" NAME="toc9">See Also</A> </P> <LI><P><A HREF="#sect10" NAME="toc10">Copyright</A> </P> </UL> </BODY> </HTML>