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https://issues.apache.org/jira/browse/HDFS-11352?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Erik Krogen updated HDFS-11352:
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    Attachment: HDFS-11352-branch-2.7.000.patch

Attaching patch with the (one-line) fix.

> Potential deadlock in NN when failing over
> ------------------------------------------
>
>                 Key: HDFS-11352
>                 URL: https://issues.apache.org/jira/browse/HDFS-11352
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.7.4, 2.6.6
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>              Labels: high-availability
>         Attachments: HDFS-11352-branch-2.7.000.patch
>
>
> HDFS-11180 fixed a general class of deadlock that can occur when failing over 
>  between the MetricsSystemImpl and FSEditLog (see comments on that JIRA for 
> more details). In trunk and branch-2/branch-2.8 this fix was successful by 
> making the metrics calls not synchronize on FSEditLog.
> In branch-2.6 and branch-2.7 there is one more method, 
> {{FSNamesystem#getTransactionsSinceLastCheckpoint}}, which still requires the 
> lock on FSEditLog and thus can result in the same deadlock scenario. This can 
> be seen by running {{TestFSNamesystemMBean#testWithFSEditLogLock}} _with the 
> patch in HDFS-11290_ on either of these branches (it fails currently).



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