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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3981) access time is set without holding writelock in FSNamesystem
Date Thu, 27 Sep 2012 07:16:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3981?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13464515#comment-13464515
] 

Konstantin Shvachko commented on HDFS-3981:
-------------------------------------------

Xiaobo, you are right this seems to be the problem. It actually even worth, because {{getBlockLocations()}}
is forced to change read lock to write lock every time when times don't need to be updated,
which is supposed to be the main fork-flow.
I traced this problem back all the way to 0.22 version. So I made this issue targeted for
0.23.4.
I put a short summary in the description field, and moved your detailed one to the previous
comment. Please follow this practice in the future as the description is emailed with every
jira comment or update.
                
> access time is set without holding writelock in FSNamesystem
> ------------------------------------------------------------
>
>                 Key: HDFS-3981
>                 URL: https://issues.apache.org/jira/browse/HDFS-3981
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.23.3
>            Reporter: Xiaobo Peng
>            Assignee: Xiaobo Peng
>            Priority: Minor
>
> Incorrect condition in {{FSNamesystem.getBlockLocatoins()}} can lead to updating times
without write lock. In most cases this condition will force {{FSNamesystem.getBlockLocatoins()}}
to hold write lock, even if times do not need to be updated.

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