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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Updated: (MAPREDUCE-1342) Potential JT deadlock in faulty TT tracking
Date Tue, 29 Dec 2009 02:08:29 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated MAPREDUCE-1342:
-----------------------------------

    Attachment: cycle0.png

Here's the output from jcarder that shows the cycle (this was detected while running TestLostTracker
with jcarder instrumentation using the branch at http://github.com/toddlipcon/jcarder/tree/cloudera)

> 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: 0.22.0
>            Reporter: Todd Lipcon
>         Attachments: cycle0.png
>
>
> 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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