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From "Aaron Kimball (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1499) JobTracker.finalizeJob inverts lock order and causes potential deadlock
Date Wed, 24 Feb 2010 04:53:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12837626#action_12837626
] 

Aaron Kimball commented on MAPREDUCE-1499:
------------------------------------------

The JobTracker lock is not the issue. finalizeJob locks the JobTracker's TaskScheduler instance
after taking the lock on the JobTracker itself. Per MAPREDUCE-1436, the lock order is JT ->
TS -> JIP. Locking JT -> JIP -> TS is a deadlock. This patch adds locks on the TaskScheduler
instance to ensure the correct order is held.

> JobTracker.finalizeJob inverts lock order and causes potential deadlock
> -----------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1499
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1499
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker
>    Affects Versions: 0.20.1, 0.20.2
>            Reporter: Todd Lipcon
>            Assignee: Aaron Kimball
>            Priority: Critical
>         Attachments: jcarder_result_1.dot.png, jcarder_result_8.dot.png, MAPREDUCE-1499.patch
>
>
> This issue was brought up by Matei in MAPREDUCE-1436 as a fairsched bug, but it turns
out it's a JT bug even with the fifo scheduler in unpatched 0.20.2. JobTracker.finalizeJob
locks JT.jobs, JT.taskScheduler, etc, having gotten the JIP log before the JT lock.

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