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https://issues.apache.org/jira/browse/YARN-4416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15056470#comment-15056470
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Naganarasimha G R commented on YARN-4416:
-----------------------------------------
Hi [~wangda], YARN-4416.v2.002.patch removed synchronized lock on
getNumApplications.
but i presume there will be possibility that in between
{{getNumPendingApplications}} and {{getNumActiveApplications}} that
{{activateApplications}} can be called and number of applications count can be
given as a wrong value(*more than actual*). Shall i revert for this ?
> 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, 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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