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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3860) HeartbeatManager#Monitor may wrongly hold the writelock of namesystem
Date Tue, 28 Aug 2012 17:24:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13443292#comment-13443292
] 

Jing Zhao commented on HDFS-3860:
---------------------------------

I just checked all the invocation of namesystem#writelock / writeunlock, and did not find
similar problems. I will check other similar code too.
                
> HeartbeatManager#Monitor may wrongly hold the writelock of namesystem
> ---------------------------------------------------------------------
>
>                 Key: HDFS-3860
>                 URL: https://issues.apache.org/jira/browse/HDFS-3860
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 3.0.0
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>             Fix For: 2.2.0-alpha
>
>         Attachments: HDFS-3860.patch, HDFS-heartbeat-testcase.patch
>
>
> In HeartbeatManager#heartbeatCheck, if some dead datanode is found, the monitor thread
will acquire the write lock of namesystem, and recheck the safemode. If it is in safemode,
the monitor thread will return from the heartbeatCheck function without release the write
lock. This may cause the monitor thread wrongly holding the write lock forever.
> The attached test case tries to simulate this bad scenario.

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