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https://issues.apache.org/jira/browse/HDFS-1542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12973992#action_12973992
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Todd Lipcon commented on HDFS-1542:
-----------------------------------

It will also happen if any DN in the pipeline fails or is inaccessible from the 
client, I believe. Basically anything that makes DFSOutputStream go and ask the 
conf for something will cause this issue.

> Deadlock in Configuration.writeXml when serialized form is larger than one 
> DFS block
> ------------------------------------------------------------------------------------
>
>                 Key: HDFS-1542
>                 URL: https://issues.apache.org/jira/browse/HDFS-1542
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>    Affects Versions: 0.20.2, 0.22.0, 0.23.0
>            Reporter: Todd Lipcon
>            Priority: Critical
>         Attachments: deadlock.txt, Test.java
>
>
> Configuration.writeXml holds a lock on itself and then writes the XML to an 
> output stream, during which DFSOutputStream will try to get a lock on 
> ackQueue/dataQueue. Meanwihle the DataStreamer thread will call functions 
> like conf.getInt() and deadlock against the other thread, since it could be 
> the same conf object.
> This causes a deterministic deadlock whenever the serialized form is larger 
> than block size.

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