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https://issues.apache.org/jira/browse/HADOOP-1461?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy updated HADOOP-1461:
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Attachment: main_taskcleanup_deadlock.txt
> Corner-case deadlock in TaskTracker
> -----------------------------------
>
> Key: HADOOP-1461
> URL: https://issues.apache.org/jira/browse/HADOOP-1461
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.12.3
> Reporter: Arun C Murthy
> Assignee: Arun C Murthy
> Priority: Critical
> Fix For: 0.14.0
>
> Attachments: main_taskcleanup_deadlock.txt
>
>
> Thanks to Koji for the attached stack-trace...
> Summary:
> main()
> -> offerService()
> -> markUnresponsiveTasks (locks the TaskTracker here)
> -> purgeTask()
> -> removeTaskFromJob (waiting to lock the RunningJob object)
> taskCleanup
> -> purgeJob (locks the RunningJob object)
> -> TIP.jobHasFinished()
> -> TIP.cleanup (waiting to lock the TaskTracker)
> -*-*-
> Clear-case of ordering issues during synchronization... it's a corner-case
> since it depends on the child-vm getting unresponsive _and_ the cleanup
> thread kicking in; which is why I'm marking this for 0.14.0 rather than
> 0.13.0 - what do others think about this?
> -*-*-
> Two possible solutions to break the deadlock cycle:
> a) Make TaskTracker.purgeJob a synchronized method, thus it locks the
> TaskTracker before locking the RunningJob method.
> b) Make the TaskTracker.tasks map a *Collections.synchronizedMap*, thus doing
> away with the need to lock the TaskTracker in TIP.cleanup
> I'd prefer a) since the TaskTracker.tasks is referenced in multiple places in
> synchronized methods... and hence is a less intrusive change.
> -*-*-
> Thoughts?
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