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https://issues.apache.org/jira/browse/HDFS-5832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13881927#comment-13881927
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Rakesh R commented on HDFS-5832:
--------------------------------
Thanks Uma for the interest.
Looks like similar, but I could see still there is a chance of reverse locking
in the code.
I'm seeing the following code flow like,
- In one side, when running SafeModeMonitor thread, it is invoking
safeMode#canLeave() by acquiring 'safeMode.this' lock and here it is asking for
the DataNodeManger#getNumLiveDataNodes by trying to acquire 'datanodeMap' lock.
- On the other side, DN heartbeat comes and DatanodeManager#handleHeartbeat()
has acquired 'datanodeMap' lock and calling namesystem#isInSafeMode(), which
inturn trying to acquire 'safeModeInfo.this' lock
> Deadeadlock found in NN between SafeMode#canLeave and
> DatanodeManager#handleHeartbeat
> -------------------------------------------------------------------------------------
>
> Key: HDFS-5832
> URL: https://issues.apache.org/jira/browse/HDFS-5832
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.0.0
> Reporter: Rakesh R
> Assignee: Rakesh R
> Priority: Blocker
> Attachments: HDFS-5832.patch, jcarder_nn_deadlock.gif
>
>
> Found the deadlock during the Namenode startup. Attached jcarder report which
> shows the cycles about the deadlock situation.
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