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https://issues.apache.org/jira/browse/HADOOP-1970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12532075
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Hudson commented on HADOOP-1970:
--------------------------------
Integrated in Hadoop-Nightly #259 (See
[http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Nightly/259/])
> tasktracker hang in reduce. Deadlock between main and comm thread
> -----------------------------------------------------------------
>
> Key: HADOOP-1970
> URL: https://issues.apache.org/jira/browse/HADOOP-1970
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.14.1
> Reporter: Koji Noguchi
> Assignee: Vivek Ratan
> Priority: Blocker
> Fix For: 0.14.2
>
> Attachments: 1970_patch01, 1970_patch02
>
>
> Saw one reduce task stuck on copy.
> jstack on the reduce task(task_200709272248_0001_r_000150_0) process showed
> {noformat}
> Found one Java-level deadlock:
> =============================
> "Comm thread for task_200709272248_0001_r_000150_0":
> waiting to lock monitor 0x08144020 (object 0xd4e30aa8, a
> org.apache.hadoop.util.Progress),
> which is held by "main"
> "main":
> waiting to lock monitor 0x08144084 (object 0xd4e30958, a
> org.apache.hadoop.util.Progress),
> which is held by "Comm thread for task_200709272248_0001_r_000150_0"
> Java stack information for the threads listed above:
> ===================================================
> "Comm thread for task_200709272248_0001_r_000150_0":
> at org.apache.hadoop.util.Progress.toString(Progress.java:113)
> - waiting to lock <0xd4e30aa8> (a org.apache.hadoop.util.Progress)
> at org.apache.hadoop.util.Progress.toString(Progress.java:116)
> - locked <0xd4e30958> (a org.apache.hadoop.util.Progress)
> at org.apache.hadoop.util.Progress.toString(Progress.java:108)
> at org.apache.hadoop.mapred.Task$1.run(Task.java:268)
> at java.lang.Thread.run(Thread.java:619)
> "main":
> at org.apache.hadoop.util.Progress.startNextPhase(Progress.java:58)
> - waiting to lock <0xd4e30958> (a org.apache.hadoop.util.Progress)
> at org.apache.hadoop.util.Progress.complete(Progress.java:70)
> - locked <0xd4e30aa8> (a org.apache.hadoop.util.Progress)
> at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:253)
> at
> org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:1777)
> {noformat}
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