mirror of https://github.com/PCSX2/pcsx2.git
169 lines
7.1 KiB
HTML
169 lines
7.1 KiB
HTML
<!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">
|
||
<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_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>
|