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From "Iyappan Srinivasan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1342) Potential JT deadlock in faulty TT tracking
Date Wed, 13 Jan 2010 05:01:54 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12799576#action_12799576
] 

Iyappan Srinivasan commented on MAPREDUCE-1342:
-----------------------------------------------

+1 for QA
Tested both global blacklisting through health scripts as well as through task attempt killing.
Also tested for
multiple nodes blacklisting and coming out of blacklisting. The UI also reflects the changes
correctly.



> 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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