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https://issues.apache.org/jira/browse/JCR-935?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12524579
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Esteban Franqueiro commented on JCR-935:
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Regarding the NPE that Pablo mentioned, it looks like a race condition, because
the code first checks for != null, and then you get an NPE. The problem seems
to disappear by synchronizing the pull(), connect(), reconnect(), disconnect(),
isConnected(), isStale() and hasOverlayedState() methods. According to the
results of the test Pablo mentioned, it seems that sync'ing these methods
doesn't add too much serialization. Still. we're wondering what do you all
think about this, because although it works in the test, we don't know if
there's a better (or may be correct) way of solving this issue.
Regards,
Esteban
> ConcurrentModificationException during logout (cont'd)
> ------------------------------------------------------
>
> Key: JCR-935
> URL: https://issues.apache.org/jira/browse/JCR-935
> Project: Jackrabbit
> Issue Type: Bug
> Components: core
> Affects Versions: 1.3
> Reporter: Pablo Rios
>
> I "seldom" get a CME running ConcurrentReadWriteTest.testReadWrite test.
> Following are different stack traces of two runs:
>
> Exception in thread "Thread-9" java.util.ConcurrentModificationException
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.checkMod(AbstractReferenceMap.java:761)
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.hasNext(AbstractReferenceMap.java:735)
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceValues.toArray(AbstractReferenceMap.java:543)
> at java.util.Collections$UnmodifiableCollection.toArray(Unknown Source)
> at java.util.Collections$UnmodifiableCollection.toArray(Unknown Source)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.dispose(LocalItemStateManager.java:341)
> at
> org.apache.jackrabbit.core.state.SessionItemStateManager.dispose(SessionItemStateManager.java:316)
> at org.apache.jackrabbit.core.SessionImpl.logout(SessionImpl.java:1269)
> at org.apache.jackrabbit.core.XASessionImpl.logout(XASessionImpl.java:379)
> at
> org.apache.jackrabbit.core.AbstractConcurrencyTest$Executor.run(AbstractConcurrencyTest.java:114)
> at java.lang.Thread.run(Unknown Source)
> Exception in thread "Thread-9" java.util.ConcurrentModificationException
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.checkMod(AbstractReferenceMap.java:761)
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.nextEntry(AbstractReferenceMap.java:770)
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceValuesIterator.next(AbstractReferenceMap.java:829)
> at
> org.apache.commons.collections.map.AbstractReferenceMap$ReferenceValues.toArray(AbstractReferenceMap.java:544)
> at java.util.Collections$UnmodifiableCollection.toArray(Unknown Source)
> at java.util.Collections$UnmodifiableCollection.toArray(Unknown Source)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.dispose(LocalItemStateManager.java:341)
> at
> org.apache.jackrabbit.core.state.SessionItemStateManager.dispose(SessionItemStateManager.java:316)
> at org.apache.jackrabbit.core.SessionImpl.logout(SessionImpl.java:1269)
> at
> org.apache.jackrabbit.core.XASessionImpl.logout(XASessionImpl.java:379)
> at
> org.apache.jackrabbit.core.AbstractConcurrencyTest$Executor.run(AbstractConcurrencyTest.java:114)
> at java.lang.Thread.run(Unknown Source)
> My working copy is revision 538918 with both JCR-314 patches applied, using
> FineGrainedISMLocking strategy.
> I run this test manually from within Eclipse 3.2.1 / JRE 1.5.0_10-b03.
> The workstation were I run this test has an Intel Dual-Core Xeon 5130 2 GHz.
> To able to compare this CPU with another, with the default params of this
> test (NUM_NODES = 5, NUM_THREADS = 5, RUN_NUM_SECONDS = 20), the number of
> operations are ~ #writes performed: 300-400, #reads performed: 4700000 -
> 4900000.
> Regards,
> Pablo
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