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From "Igor Bolotin (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-139) Deadlock in LocalFileSystem lock/release
Date Sat, 15 Apr 2006 05:42:01 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-139?page=all ]

Igor Bolotin updated HADOOP-139:
--------------------------------

    Attachment: deadlock.patch

Attached is proposed patch. I removed entire lock/release method synchronization and replaced
it with critical section synchronization for sets accesses - leaving channel lock/release
calls outside of synchronized statement. 

> Deadlock in LocalFileSystem lock/release
> ----------------------------------------
>
>          Key: HADOOP-139
>          URL: http://issues.apache.org/jira/browse/HADOOP-139
>      Project: Hadoop
>         Type: Bug

>   Components: fs
>     Reporter: Igor Bolotin
>  Attachments: deadlock.patch
>
> LocalFileSystem lock/release methods marked synchronized and inside they lock file channel
- this produces deadlock situation. Let's see how it happens: 
> 1. First thread locks the file and starts some long-running process.
> 2. Second thread tries to lock the file and it blocks inside channel lock method. It
 keeps LocalFileSystem instance "locked" as well. 
> 3. First thread finished it's processing and tries to release lock - it blocks because
LocalFileSystem instance is "locked" by second thread - both threads are waiting to each other.


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