Code Correctness: Double-Checked Locking - Revision history

KirstenS at 23:25, 7 April 2009

2009-04-07T23:25:02Z

KirstenS at 11:13, 11 February 2009

2009-02-11T11:13:23Z

KirstenS at 11:56, 29 October 2008

2008-10-29T11:56:52Z

KirstenS at 11:03, 23 September 2008

2008-09-23T11:03:21Z

Weilin Zhong at 16:47, 19 July 2006

2006-07-19T16:47:50Z

Weilin Zhong at 14:51, 19 July 2006

2006-07-19T14:51:50Z

Weilin Zhong at 14:04, 19 July 2006

2006-07-19T14:04:58Z

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==Abstract==

Double-checked locking is an incorrect idiom that does not achieve the intended effect.

==Description==

Many talented individuals have spent a great deal of time pondering ways to make double-checked locking work in order to improve performance. None have succeeded.

==Examples ==

At first blush it may seem that the following bit of code achieves thread safety while avoiding unnecessary synchronization.

<pre>
if (fitz == null) {
synchronized (this) {
if (fitz == null) {
fitz = new Fitzer();
}
}
}
return fitz;
</pre>

The programmer wants to guarantee that only one Fitzer() object is ever allocated, but does not want to pay the cost of synchronization every time this code is called. This idiom is known as double-checked locking.

Unfortunately, it does not work, and multiple Fitzer() objects can be allocated. See The "Double-Checked Locking is Broken" Declaration for more details [1].

==Related Threats==

==Related Attacks==

==Related Vulnerabilities==

==Related Countermeasures==

==References==

[1] D. Bacon et al. The "Double-Checked Locking is Broken" Declaration. http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html.

==Categories==

[[Category:Synchronization and Timing Vulnerability]]

[[Category:Java]]

[[Category:Implementation]]

[[Category:Code Snippet]]

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-Double-checked locking is an incorrect idiom that does not achieve the intended effect.
+[[ASDR_TOC_Vulnerabilities|Vulnerabilities Table of Contents]]
 ==Description==
 Many talented individuals have spent a great deal of time pondering ways to make double-checked locking work in order to improve performance. None have succeeded.
 ==Examples ==
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-==Related Threats==
+==Related [[Attacks]]==
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+==Related [[Vulnerabilities]]==
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 ==References==
-[1] D. Bacon et al. The "Double-Checked Locking is Broken" Declaration. http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html.
+* [[1] D. Bacon et al. The "Double-Checked Locking is Broken" Declaration. http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html.
 [[Category:Synchronization and Timing Vulnerability]]
 [[Category:Java]]
 [[Category:Implementation]]
 [[Category:Code Snippet]]