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Date: Thu, 25 Feb 2010 01:22:27 +0000 (UTC)
From: "Matei Zaharia (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1499) JobTracker.finalizeJob inverts
 lock order and causes potential deadlock
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838131#action_12838131 ] 

Matei Zaharia commented on MAPREDUCE-1499:
------------------------------------------

The problem in MAPREDUCE-1436 only happened with a backport of the trunk fair scheduler to 0.20. It probably won't happen with the 0.20 fair scheduler. However, anyone packaging a distribution that includes a backport of the fair scheduler should look into it. As I mentioned in MAPREDUCE-1436, the fix (adding a lock around the TaskTrackerManager in update() is simple and is unlikely to have a major impact on performance.

> 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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