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Date: Sat, 17 Sep 2011 00:31:08 +0000 (UTC)
From: "stack (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-4367) Deadlock in MemStore flusher due to
 JDK internally synchronizing on current thread
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    [ https://issues.apache.org/jira/browse/HBASE-4367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13106957#comment-13106957 ] 

stack commented on HBASE-4367:
------------------------------

We can do without the removal of the Date from PriorityCompactionQueue (There is no PCQ in TRUNK as it happens).

> Deadlock in MemStore flusher due to JDK internally synchronizing on current thread
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-4367
>                 URL: https://issues.apache.org/jira/browse/HBASE-4367
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.90.4
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.92.0
>
>         Attachments: 4367.txt, hbase-4367.txt
>
>
> We observed a deadlock in production between the following threads:
> - IPC handler thread holding the monitor lock on MemStoreFlusher inside reclaimMemStoreMemory, waiting to obtain MemStoreFlusher.lock (the reentrant lock member)
> - cacheFlusher thread inside flushRegion holds MemStoreFlusher.lock, and then calls PriorityCompactionQueue.add, which calls PriorityCompactionQueue.addToRegionsInQueue, which calls CompactionRequest.toString(), which calls Date.toString. If this occurs just after a GC under memory pressure, Date.toString needs to reload locale information (stored in a soft reference), so it calls ResourceBundle.loadBundle, which uses Thread.currentThread() as a synchronizer (see sun bug http://bugs.sun.com/view_bug.do?bug_id=6915621). Since the current thread is the MemStoreFlusher itself, we have a lock order inversion and a deadlock.

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