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Posted to hdfs-issues@hadoop.apache.org by "emopers (JIRA)" <ji...@apache.org> on 2016/01/14 14:59:39 UTC

[jira] [Updated] (HDFS-9649) NNStorage does not synchronize iteration on a synchronized list

     [ https://issues.apache.org/jira/browse/HDFS-9649?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

emopers updated HDFS-9649:
--------------------------
    Attachment: HDFS-9649.patch

> NNStorage does not synchronize iteration on a synchronized list
> ---------------------------------------------------------------
>
>                 Key: HDFS-9649
>                 URL: https://issues.apache.org/jira/browse/HDFS-9649
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: emopers
>         Attachments: HDFS-9649.patch
>
>
> In line 839 of NNStroage.java#reportErrorsOnDirectories, the synchronized list, `sds` is iterated in an unsynchronized manner, but according to [Oracle Java 7 API specification](http://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#synchronizedList(java.util.List)),
> this is not thread-safe and can lead to non-deterministic behavior.
> This could be fix by synchronizing the iteration on `sds`. The synchronized list is passed to method `reportErrorsOnDirectories` from (https://github.com/facebookarchive/hadoop-20/blob/2a29bc6ecf30edb1ad8dbde32aa49a317b4d44f4/src/hdfs/org/apache/hadoop/hdfs/server/namenode/FSImage.java#L508)
> I have already submitted submitted a PR at https://github.com/apache/hadoop/pull/64 . Let me know if it looks good so that I can generate patch and submit it.



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