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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1499) JobTracker.finalizeJob inverts lock order and causes potential deadlock
Date Wed, 24 Feb 2010 10:26:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12837735#action_12837735
] 

Amar Kamat commented on MAPREDUCE-1499:
---------------------------------------

Aaron,
JT->TS->JIP and JT->JIP->TS is not a deadlock.  What Amareshwari is trying to
say is that if the parent level lock is same (JT in this case) then the child locking order
doesnt really matter. Also the code which you have fixed is in RecoveryManager which runs
before the JobTracker becomes RUNNING and the tasktracker connects to the jobtracker. I dont
think MAPREDUCE-1436 is a duplicate of MAPREDUCE-1499.

> 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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