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Date: Mon, 14 Dec 2015 19:09:46 +0000 (UTC)
From: "Naganarasimha G R (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
Message-ID: <JIRA.12918093.1449169796000.17044.1450120186962@Atlassian.JIRA>
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 <JIRA.12918093.1449169796741@arcas>
Subject: [jira] [Updated] (YARN-4416) Deadlock due to synchronised get
 Methods in AbstractCSQueue
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     [ https://issues.apache.org/jira/browse/YARN-4416?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Naganarasimha G R updated YARN-4416:
------------------------------------
    Attachment: YARN-4416.v2.003.patch

Reverting the removal of lock on {{LeafQueue.getNumApplications}}

> 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
>         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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