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| author | rpj <rpj> | 2005-05-05 14:18:27 +0000 |
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| committer | rpj <rpj> | 2005-05-05 14:18:27 +0000 |
| commit | 41f88a82b33cdb357c83b582381232733ed2d039 (patch) | |
| tree | b3690e999b4d934fce7aab79b2693ab086a4ad46 /manual/pthread_rwlock_rdlock.html | |
| parent | b75686484d99c90317b64184ce5080093ee7d2a9 (diff) | |
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diff --git a/manual/pthread_rwlock_rdlock.html b/manual/pthread_rwlock_rdlock.html new file mode 100644 index 0000000..ed56cb5 --- /dev/null +++ b/manual/pthread_rwlock_rdlock.html @@ -0,0 +1,166 @@ +<!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_RDLOCK"(P) manual page</TITLE> + <META NAME="GENERATOR" CONTENT="OpenOffice.org 1.1.3 (Linux)"> + <META NAME="CREATED" CONTENT="20050505;10352600"> + <META NAME="CHANGED" CONTENT="20050505;12554200"> + <!-- manual page source format generated by PolyglotMan v3.2, --> + <!-- available at http://polyglotman.sourceforge.net/ --> +</HEAD> +<BODY LANG="en-GB" BGCOLOR="#ffffff" DIR="LTR"> +<P><A HREF="#toc">Table of Contents</A></P> +<H2><A HREF="#toc0" NAME="sect0">Name</A></H2> +<P>pthread_rwlock_rdlock, pthread_rwlock_tryrdlock - lock a +read-write lock object for reading +</P> +<H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> +<P><B>#include <pthread.h> </B> +</P> +<P><B>int pthread_rwlock_rdlock(pthread_rwlock_t <I>*</I></B><I>rwlock</I><B>); +<BR></B>i<B>nt pthread_rwlock_tryrdlock(pthread_rwlock_t <I>*</I></B><I>rwlock</I><B>); +</B> +</P> +<H2><A HREF="#toc2" NAME="sect2">Description</A></H2> +<P>The <B>pthread_rwlock_rdlock</B> function shall apply a read lock +to the read-write lock referenced by <I>rwlock</I>. The calling +thread acquires the read lock if a writer does not hold the lock and +there are no writers blocked on the lock. +</P> +<P><B>Pthreads-win32</B> does not prefer either writers or readers in +acquiring the lock – all threads enter a single prioritised FIFO +queue. While this may not be optimally efficient for some +applications, it does ensure that one type does not starve the other.</P> +<P>A thread may hold multiple concurrent read locks on <I>rwlock</I> +(that is, successfully call the <B>pthread_rwlock_rdlock</B> function +<I>n</I> times). If so, the application shall ensure that the thread +performs matching unlocks (that is, it calls the +<A HREF="pthread_rwlock_unlock.html"><B>pthread_rwlock_unlock</B>(3)</A> +function <I>n</I> times). +</P> +<P>The <B>pthread_rwlock_tryrdlock</B> function shall apply a read +lock as in the <B>pthread_rwlock_rdlock</B> function, with the +exception that the function shall fail if the equivalent +<B>pthread_rwlock_rdlock</B> call would have blocked the calling +thread. In no case shall the <B>pthread_rwlock_tryrdlock</B> function +ever block; it always either acquires the lock or fails and returns +immediately. +</P> +<P>Results are undefined if any of these functions are called with an +uninitialized read-write lock. +</P> +<P><B>Pthreads-w32</B> does not detect deadlock if the thread already +owns the lock for writing.</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_rdlock</B> function shall +return zero; otherwise, an error number shall be returned to indicate +the error. +</P> +<P>The <B>pthread_rwlock_tryrdlock</B> function shall return zero if +the lock for reading on the read-write lock object referenced by +<I>rwlock</I> is acquired. 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_rwlock_tryrdlock</B> function shall fail if: +</P> +<DL> + <DT><B>EBUSY</B> + </DT><DD STYLE="margin-bottom: 0.5cm"> + The read-write lock could not be acquired for reading because a + writer holds the lock or a writer with the appropriate priority was + blocked on it. + </DD></DL> +<P> +The <B>pthread_rwlock_rdlock</B> and <B>pthread_rwlock_tryrdlock</B> +functions may fail if: +</P> +<DL> + <DT><B>EINVAL</B> + </DT><DD> + The value specified by <I>rwlock</I> does not refer to an + initialized read-write lock object. + </DD><DT> + <B>EAGAIN</B> + </DT><DD STYLE="margin-bottom: 0.5cm"> + The read lock could not be acquired because the maximum number of + read locks for <I>rwlock</I> has been exceeded. + </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 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_init.html"><B>pthread_rwlock_destroy</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_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> |