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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-14912) FairCallQueue may defer servicing calls
Date Fri, 29 Sep 2017 15:27:00 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-14912?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jason Lowe updated HADOOP-14912:
--------------------------------
    Affects Version/s: 2.9.0
                       3.0.0-alpha4
     Target Version/s: 2.9.0, 2.8.3, 3.0.0  (was: 2.8.3)

Thanks for the report and patch!  The unit tests appear to be unrelated.

Nit: The following code is now dead and should be removed:
{code}
    // guaranteed to find an element if caller acquired permit.
    assert e != null : "consumer didn't acquire semaphore!";
{code}


> FairCallQueue may defer servicing calls
> ---------------------------------------
>
>                 Key: HADOOP-14912
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14912
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: ipc
>    Affects Versions: 2.9.0, 3.0.0-alpha4, 2.8.2
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>         Attachments: HADOOP-14912.patch
>
>
> HADOOP-14033 switched a lock to a semaphore to allow concurrency for producers &
consumers to the underlying queues.  A race condition was created that may cause a consumer
to acquire a permit but not extract an element, leaving the semaphore with fewer permits than
queued elements.  This causes a minimum number of calls to always be present in the call queue.



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