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From "Naganarasimha G R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4416) Deadlock due to synchronised get Methods in AbstractCSQueue
Date Fri, 18 Dec 2015 00:32:46 GMT

    [ https://issues.apache.org/jira/browse/YARN-4416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15063172#comment-15063172

Naganarasimha G R commented on YARN-4416:

Thanks for the review and commit [~wangda] & [~sunilg]

> Deadlock due to synchronised get Methods in AbstractCSQueue
> -----------------------------------------------------------
>                 Key: YARN-4416
>                 URL: https://issues.apache.org/jira/browse/YARN-4416
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: capacity scheduler, resourcemanager
>    Affects Versions: 2.7.1
>            Reporter: Naganarasimha G R
>            Assignee: Naganarasimha G R
>            Priority: Minor
>             Fix For: 2.8.0
>         Attachments: YARN-4416.v1.001.patch, YARN-4416.v1.002.patch, YARN-4416.v2.001.patch,
YARN-4416.v2.002.patch, YARN-4416.v2.003.patch, deadlock.log
> While debugging in eclipse came across a scenario where in i had to get to know the name
of the queue but every time i tried to see the queue it was getting hung. On seeing the stack
realized there was a deadlock but on analysis found out that it was only due to *queue.toString()*
during debugging as {{AbstractCSQueue.getAbsoluteUsedCapacity}} was synchronized.
> Hence we need to ensure following :
> # queueCapacity, resource-usage has their own read/write lock hence synchronization is
not req
> # numContainers is volatile hence synchronization is not req.
> # read/write lock could be added to Ordering Policy. Read operations don't need synchronized.
So {{getNumApplications}} doesn't need synchronized. 
> (First 2 will be handled in this jira and the third will be handled in YARN-4443)

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