58 lines
2.4 KiB
HTML
58 lines
2.4 KiB
HTML
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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>Read/write locks do not favor writers</title>
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<!-- Begin Header Records ========================================== -->
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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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<!-- Change History: -->
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<!-- YYMMDD USERID Change description -->
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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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<h2>Read/write locks do not favor writers</h2>
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<p>The i5/OS implementation of read/write locks does not favor writers. If
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your application has a large number of readers contending for the same lock,
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the writers may not be allowed to write.</p>
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<p>The i5/OS implementation of <strong>pthread_rwlock_tryrdlock</strong>(),
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for example, does not completely honor the Single UNIX Specification in its
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treatment of reader/writer contention.</p>
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<p>The standard states the following: "The function pthread_rwlock_tryrdlock()
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applies a read lock as in the pthread_rwlock_rdlock() function with the
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exception that the function fails if any thread holds a write lock on rwlock or
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there are writers blocked on rwlock."</p>
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<p>In the i5/OS implementation, if <strong>pthread_rwlock_tryrdlock</strong>()
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is used on a read/write lock that has multiple readers holding the lock and
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multiple waiting writers blocked on the lock, the <strong>
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pthread_rwlock_tryrdlock</strong>() are allowed to complete successfully.</p>
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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">
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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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