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https://issues.apache.org/jira/browse/DERBY-6879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15362707#comment-15362707
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Brett Bergquist commented on DERBY-6879:
----------------------------------------
The patch also makes the CancelXATransactionTask.cancel and the
CancelXATransactionTask.run methods synchronized. Without this there is the
possibility that the "xaState" could become null within "cancel" but be
accessed within "run" and a NPE could occur.
> Engine deadlock between XA timeout handling and cleanupOnError
> --------------------------------------------------------------
>
> Key: DERBY-6879
> URL: https://issues.apache.org/jira/browse/DERBY-6879
> Project: Derby
> Issue Type: Bug
> Components: Services
> Affects Versions: 10.10.2.0
> Environment: Solaris 10.5 on Oracle M5000
> Reporter: Brett Bergquist
> Attachments: derby-6879-test-2.diff, derby-6879-test.diff
>
>
> Deadlock between XA timer cleanup task and the ContextManager.cleanupOnError
> Found one Java-level deadlock:
> =============================
> "DRDAConnThread_34":
> waiting to lock monitor 0x0000000104b14d18 (object 0xfffffffd9090f058, a
> org.apache.derby.jdbc.XATransactionState),
> which is held by "Timer-0"
> "Timer-0":
> waiting to lock monitor 0x00000001038b96e8 (object 0xfffffffd9090d8b0, a
> org.apache.derby.impl.jdbc.EmbedConnection40),
> which is held by "DRDAConnThread_34"
>
> Java stack information for the threads listed above:
> ===================================================
> "DRDAConnThread_34":
> at org.apache.derby.jdbc.XATransactionState.cleanupOnError(Unknown
> Source)
> - waiting to lock <0xfffffffd9090f058> (a
> org.apache.derby.jdbc.XATransactionState)
> at
> org.apache.derby.iapi.services.context.ContextManager.cleanupOnError(Unknown
> Source)
> at
> org.apache.derby.impl.jdbc.TransactionResourceImpl.cleanupOnError(Unknown
> Source)
> at
> org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown
> Source)
> at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(Unknown
> Source)
> - locked <0xfffffffd9090d8b0> (a
> org.apache.derby.impl.jdbc.EmbedConnection40)
> at
> org.apache.derby.impl.jdbc.EmbedPreparedStatement.executeStatement(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedPreparedStatement.execute(Unknown
> Source)
> at org.apache.derby.iapi.jdbc.BrokeredPreparedStatement.execute(Unknown
> Source)
> at org.apache.derby.impl.drda.DRDAStatement.execute(Unknown Source)
> at
> org.apache.derby.impl.drda.DRDAConnThread.parseEXCSQLSTTobjects(Unknown
> Source)
> at org.apache.derby.impl.drda.DRDAConnThread.parseEXCSQLSTT(Unknown
> Source)
> at org.apache.derby.impl.drda.DRDAConnThread.processCommands(Unknown
> Source)
> at org.apache.derby.impl.drda.DRDAConnThread.run(Unknown Source)
> "Timer-0":
> at org.apache.derby.impl.jdbc.EmbedConnection.xa_rollback(Unknown Source)
> - waiting to lock <0xfffffffd9090d8b0> (a
> org.apache.derby.impl.jdbc.EmbedConnection40)
> at org.apache.derby.jdbc.XATransactionState.cancel(Unknown Source)
> - locked <0xfffffffd9090f058> (a
> org.apache.derby.jdbc.XATransactionState)
> at
> org.apache.derby.jdbc.XATransactionState$CancelXATransactionTask.run(Unknown
> Source)
> at java.util.TimerThread.mainLoop(Timer.java:555)
> at java.util.TimerThread.run(Timer.java:505)
>
> Found 1 deadlock.
> This deadlock caused Derby to create 18000 transaction recovery logs because
> of the XA transaction that did not cleanup in the timeout. Rebooting the
> system would cause a 50 hour boot up time to process the transaction logs so
> recovery had to be done by going to a backup database before the issue
> occurred.
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