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https://issues.apache.org/jira/browse/HADOOP-17728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17362036#comment-17362036
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Mingliang Liu commented on HADOOP-17728:
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Thanks [~Jim_Brennan]! I would like to keep it open for a while in case there
are more comments. Apparently when this patch was discussed in PR, it was
considered valid. I will follow up discussions in [HADOOP-17758].
When reporting a bug, if you find the JIRA related to the cause, you can also
comment directly on the original JIRA (e.g. this one) directly instead of
opening a new JIRA (e.g. HADOOP-17758). That way we can track the context one
place. But if the patch that is in question is not clear, opening a new one
will be better.
> Fix issue of the StatisticsDataReferenceCleaner cleanUp
> -------------------------------------------------------
>
> Key: HADOOP-17728
> URL: https://issues.apache.org/jira/browse/HADOOP-17728
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs
> Affects Versions: 3.2.1
> Reporter: yikf
> Assignee: yikf
> Priority: Minor
> Labels: pull-request-available, reverted
> Time Spent: 5h 10m
> Remaining Estimate: 0h
>
> Cleaner thread will be blocked if we remove reference from ReferenceQueue
> unless the `queue.enqueue` called.
> ----
> As shown below, We call ReferenceQueue.remove() now while cleanUp, Call
> chain as follow：
> *StatisticsDataReferenceCleaner#queue.remove() ->
> ReferenceQueue.remove(0) -> lock.wait(0)*
> But, lock.notifyAll is called when queue.enqueue only, so Cleaner thread
> will be blocked.
>
> ThreadDump:
> {code:java}
> "Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f7afc088800
> nid=0x2119 in Object.wait() [0x00007f7b00230000]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> - waiting on <0x00000000c00c2f58> (a java.lang.ref.Reference$Lock)
> at java.lang.Object.wait(Object.java:502)
> at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
> - locked <0x00000000c00c2f58> (a java.lang.ref.Reference$Lock)
> at
> java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153){code}
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