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https://issues.apache.org/jira/browse/CURATOR-276?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kezhu Wang closed CURATOR-276.
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Resolution: Duplicate
Thank you for your report. This has been fixed by CURATOR-621. I was not aware
of this before the fix.
> Downgrade pattern doesn't work with "Shared Reentrant Read Write Lock"
> ----------------------------------------------------------------------
>
> Key: CURATOR-276
> URL: https://issues.apache.org/jira/browse/CURATOR-276
> Project: Apache Curator
> Issue Type: Bug
> Components: Recipes
> Affects Versions: 2.9.1
> Environment: Windows 7
> Java 1.7.0_60
> ZooKeeper Server 3.4.6-1569965
> Reporter: Maxim Sidnin
> Priority: Major
> Attachments: DowngradeTest.java, zoo.cfg
>
>
> *Issue:* Downgrade pattern doesn't block already existed WRITE lock waiters.
> *Scenario:*
> - First thread takes a WRITE lock and waits
> - Second thread starts and it is trying to obtain a WRITE lock. It waits
> because the WRITE lock is hold by the first thread.
> - First thread does downgrade:
> -- Takes the READ lock
> -- Releases the WRITE lock
> (x) At this point the first thread still holds the READ lock but the second
> one will get the WRITE lock.
> It is reproducible for:
> - 2 threads use the same CuratorFramework instance
> - 2 threads use the different sessions
> - 2 separate JVMs
> (i) There is attached test class: *DowngradeTest.java* and zoo.cfg
> (i) Quote from Shared Reentrant Read Write Lock description
> http://curator.apache.org/curator-recipes/shared-reentrant-read-write-lock.html
> {code}
> Lock Downgrading Re-entrancy also allows downgrading from the write lock to a
> read lock, by acquiring the write lock, then the read lock and then releasing
> the write lock. However, upgrading from a read lock to the write lock is not
> possible.
> {code}
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