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Posted to hdfs-issues@hadoop.apache.org by "Colin Patrick McCabe (JIRA)" <ji...@apache.org> on 2012/07/06 20:40:34 UTC
[jira] [Resolved] (HDFS-838) libhdfs causes a segfault due to race
condition
[ https://issues.apache.org/jira/browse/HDFS-838?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Colin Patrick McCabe resolved HDFS-838.
---------------------------------------
Resolution: Fixed
Fix Version/s: 1.0.0
The call to JNI_CreateJavaVM is now done under the jvmMutex, at least in branch-1, branch-2, and trunk. So this should no longer be an issue.
> libhdfs causes a segfault due to race condition
> -----------------------------------------------
>
> Key: HDFS-838
> URL: https://issues.apache.org/jira/browse/HDFS-838
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: libhdfs
> Affects Versions: 0.20.1, 0.20.2, 0.21.0, 0.22.0
> Reporter: Brian Bockelman
> Fix For: 1.0.0
>
>
> The first libhdfs operation that is performed is not thread-safe; this is because the creation of a JVM is not protected by a mutex.
> We have been able to trigger this by doing the following:
> 1) Start a few GNOME sessions on the box. Make sure you are running the gnome volume manager. The volume manager will perform a GETATTR operation on any newly mounted file system.
> 2) Start fuse-dfs in debug mode. As soon as it starts, you will see two or more GETATTR calls almost instantly.
> 3) fuse-dfs segfaults; if you ran this with GDB, you'll see a stack trace coming from libhdfs starting up a new JVM.
> I imagine you could replicate this more simply by having two threads that call libhdfs simultaneously.
> I have a patch for fuse-dfs which avoids the problem, but we probably need to fix it in libhdfs itself.
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