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https://issues.apache.org/jira/browse/HBASE-21292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16646866#comment-16646866
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stack commented on HBASE-21292:
-------------------------------
+1
Its for sure exotic.
> IdLock.getLockEntry() may hang if interrupted
> ---------------------------------------------
>
> Key: HBASE-21292
> URL: https://issues.apache.org/jira/browse/HBASE-21292
> Project: HBase
> Issue Type: Bug
> Reporter: Allan Yang
> Assignee: Allan Yang
> Priority: Major
> Fix For: 2.1.0, 2.0.2, 1.4.9
>
> Attachments: HBASE-21292.branch-2.0.001.patch
>
>
> This is a rare case found by my colleague which really happened on our
> production env.
> Thread may hang(or enter a infinite loop ) when try to call
> IdLock.getLockEntry(). Here is the case:
> 1. Thread1 owned the IdLock, while Thread2(the only one waiting) was waiting
> for it.
> 2. Thread1 called releaseLockEntry, it will set IdLock.locked = false, but
> since Thread2 was waiting, it won't call map.remove(entry.id)
> 3. While Thread1 was calling releaseLockEntry, Thread2 was interrupted. So no
> one will remove this IdLock from the map.
> 4. If another thread try to call getLockEntry on this IdLock， it will end up
> in a infinite loop. Since existing = map.putIfAbsent(entry.id, entry)) !=
> null and existing.locked=false
> It is hard to write a UT since it is a very rare race condition.
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