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https://issues.apache.org/jira/browse/MAPREDUCE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12797545#action_12797545
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Amareshwari Sriramadasu commented on MAPREDUCE-1342:
----------------------------------------------------
JobTracker.FaultyTrackerInfo.isBlacklisted is called, holding taskTrackers
lock, from methods JobTracker.activeTaskTrackers(),
JobTracker.blacklistedTaskTrackers(), JobTracker.removeTracker(),
JobTracker.taskTrackerNames(), JobTracker.updateTaskTrackerStatus(). But
methods FaultyTrackerInfo.{remove/add}HostCapacity hold the lock on
potentiallyFaultyTrackers and then lock taskTrackers. Moreover all the callers
of FaultyTrackerInfo.{remove/add}HostCapacity hold JobTracker lock.
Discussed offline with Amar and Jothi, and we think that we should maintain the
order that taskTrackers lock first, then potentiallyFaultyTrackers lock in
methods {remove/add}HostCapacity also. Since, those methods already hold
JobTracker lock, this code change should not introduce any side-effects.
Thoughts?
> 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, mapreduce-1342-1.patch,
> mapreduce-1342-2.patch
>
>
> 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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