Bug 52356 - Prevent potential data races on "org.apache.catalina.tribes.transport.bio.util.FastQueue.size".
Summary: Prevent potential data races on "org.apache.catalina.tribes.transport.bio.uti...
Status: RESOLVED FIXED
Alias: None
Product: Tomcat 7
Classification: Unclassified
Component: Catalina (show other bugs)
Version: trunk
Hardware: PC Linux
: P2 normal (vote)
Target Milestone: ---
Assignee: Tomcat Developers Mailing List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2011-12-18 23:41 UTC by Mohsen Vakilian
Modified: 2011-12-24 00:08 UTC (History)
1 user (show)


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Description Mohsen Vakilian 2011-12-18 23:41:25 UTC 
Even though accesses to "org.apache.catalina.tribes.transport.bio.util.FastQueue.size" are synchronized inside "org.apache.catalina.tribes.transport.bio.util.FastQueue.add(ChannelMessage, Member[], InterceptorPayload)" and "org.apache.catalina.tribes.transport.bio.util.FastQueue.remove()", the read access in "org.apache.catalina.tribes.transport.bio.util.FastQueue.getSize()" is not properly synchronized and thus can lead to a race condition. However, "org.apache.catalina.tribes.transport.bio.util.FastQueue.getSize()" is not used, so this bug never manifests. Nevertheless, we suggest that Tomcat developers either remove "org.apache.catalina.tribes.transport.bio.util.FastQueue.getSize()" or make it access the shared field safely.

Field "org.apache.catalina.tribes.transport.bio.util.FastQueue.size" is declared at
<http://svn.apache.org/repos/asf/!svn/bc/1220560/tomcat/trunk/java/org/apache/catalina/tribes/transport/bio/util/FastQueue.java>.
Comment 1 Mark Thomas 2011-12-23 21:20:11 UTC 
Write access is protected by the lock. Making it volatile will ensure the latest version is available to the getSize() method.
Comment 2 Mark Thomas 2011-12-23 21:21:50 UTC 
Fixed in trunk and 7.0.x and will be included in 7.0.24 onwards.
Comment 3 Mohsen Vakilian 2011-12-24 00:08:34 UTC 
Thanks for resolving this issue. Keshmesh <http://keshmesh.cs.illinois.edu/> detected this problem when we ran it on Tomcat using method "org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor.run()" as an entry point.