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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6354) DatabaseMetaDataTest.testGetColumnsReadOnly fails with NPE when releasing page
Date Wed, 11 Dec 2013 10:43:07 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13845275#comment-13845275
] 

Knut Anders Hatlen commented on DERBY-6354:
-------------------------------------------

Thanks for looking into this, Dag. I'm not sure I've understood what the extra diagnostics
code does. It seems to write the stack trace to System.err when holdsThis == false? Will that
stack trace be any different from the one reported by the SanityManager.ASSERT() call right
below it?

I found this bug that was reported against OpenJDK: https://bugs.openjdk.java.net/browse/JDK-8028564

It sounds like a probable root cause for the NPE we're seeing. The NPE happens because we
get null from ConcurrentHashMap.get() for an entry that we expect to be there. If there's
a bug in the JDK that causes elements to be lost from ConcurrentHashMaps in certain situations,
that NPE sounds exactly like the kind of symptom one might expect.

I'll keep an eye on the bug report and ask to have the JDK upgraded on the test rigs when
the fix is available in an official build.

> DatabaseMetaDataTest.testGetColumnsReadOnly fails with NPE when releasing page
> ------------------------------------------------------------------------------
>
>                 Key: DERBY-6354
>                 URL: https://issues.apache.org/jira/browse/DERBY-6354
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.11.0.0
>            Reporter: Knut Anders Hatlen
>         Attachments: derby-6343-diag.diff, fail-solaris.zip, fail-windows.zip
>
>
> Seen twice in the nightly testing lately:
> http://download.java.net/javadesktop/derby/request_5581975/javadb-task-3729984.html
> http://download.java.net/javadesktop/derby/request_5581997/javadb-task-3730576.html
> Both failures happened with JDK 8-ea-b107 (Windows and Solaris).



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