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Date: Tue, 12 Jan 2010 22:21:54 +0000 (UTC)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1342) Potential JT deadlock in faulty
 TT tracking
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12799431#action_12799431 ] 

Todd Lipcon commented on MAPREDUCE-1342:
----------------------------------------

Now that some more methods have been made synchronized, I'd like to rerun jcarder another time, just to make sure we didn't introduce a new deadlock while fixing this one. I should have a chance to do so in the next day or two.

> Potential JT deadlock in faulty TT tracking
> -------------------------------------------
>
>                 Key: MAPREDUCE-1342
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1342
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker
>    Affects Versions: 0.20.1
>            Reporter: Todd Lipcon
>            Assignee: Amareshwari Sriramadasu
>             Fix For: 0.21.0
>
>         Attachments: cycle0.png, mapreduce-1342-1.patch, mapreduce-1342-2.patch, patch-1342-1.txt, patch-1342-2-ydist.txt, patch-1342-2.txt, patch-1342-ydist.txt, patch-1342.txt
>
>
> JT$FaultyTrackersInfo.incrementFaults first locks potentiallyFaultyTrackers, and then calls blackListTracker, which calls removeHostCapacity, which locks JT.taskTrackers
> On the other hand, JT.blacklistedTaskTrackers() locks taskTrackers, then calls faultyTrackers.isBlacklisted() which goes on to lock potentiallyFaultyTrackers.
> I haven't produced such a deadlock, but the lock ordering here is inverted and therefore could deadlock.
> Not sure if this goes back to 0.21 or just in trunk.

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