1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Release 4.8: Minor Change in Behavior of DB_MPOOLFILE->get</title>
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
<link rel="up" href="upgrade_4_8_toc.html" title="Chapter 45. Upgrading Berkeley DB 4.7 applications to Berkeley DB 4.8" />
<link rel="prev" href="upgrade_4_8_dpl.html" title="Release 4.8: Registering DPL Secondary Keys" />
<link rel="next" href="upgrade_4_8_fcntl.html" title="Release 4.8: Dropped Support for fcntl System Calls" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Release 4.8: Minor Change in Behavior of DB_MPOOLFILE->get</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="upgrade_4_8_dpl.html">Prev</a> </td>
<th width="60%" align="center">Chapter 45. Upgrading Berkeley DB 4.7 applications to Berkeley DB 4.8</th>
<td width="20%" align="right"> <a accesskey="n" href="upgrade_4_8_fcntl.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="upgrade_4_8_mpool"></a>Release 4.8: Minor Change in Behavior of DB_MPOOLFILE->get</h2>
</div>
</div>
</div>
<p>
DB 4.8 introduces some performance enhancements, based on the use
of shared/exclusive latches instead of locks in some areas of the
internal buffer management code. This change will affect how the
<code class="classname">DB_MPOOL</code> interface handles dirty buffers.
</p>
<p> Because of these
changes, <code class="methodname">DB_MPOOLFILE->get</code> will now
acquire an exclusive latch on the buffer if
the <code class="literal">DB_MPOOL_DIRTY</code>
or <code class="literal">DB_MPOOL_EDIT</code> flags are specified. This
could lead to an application deadlock if the application tries to
fetch the buffer again, without an
intervening <code class="methodname">DB_MPOOLFILE->put</code> call.
</p>
<p>
If your application uses the <code class="literal">DB_MPOOL</code>
interface, and especially the <code class="literal">DB_MPOOL_DIRTY</code>
and <code class="literal">DB_MPOOL_EDIT</code> flags, you should review your
code to ensure that this behavior change does not cause your
application to deadlock.
</p>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="upgrade_4_8_dpl.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="upgrade_4_8_toc.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="upgrade_4_8_fcntl.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Release 4.8: Registering DPL Secondary Keys </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> Release 4.8: Dropped Support for fcntl System Calls</td>
</tr>
</table>
</div>
</body>
</html>
|
