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https://issues.apache.org/jira/browse/JCR-1148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12532033
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Martijn Hendriks commented on JCR-1148:
---------------------------------------
Here are the stacktraces of two threads involved in the NPE:
The thread that throws the NPE (line information in ItemState has been changed
due to debugging code):
Thread [Thread-38] (Suspended (breakpoint at line 158 in ItemState))
NodeState(ItemState).pull() line: 158
XAItemStateManager(LocalItemStateManager).stateModified(ItemState)
line: 420
StateChangeDispatcher.notifyStateModified(ItemState) line: 85
SharedItemStateManager.stateModified(ItemState) line: 390
NodeState(ItemState).notifyStateUpdated() line: 244
ChangeLog.persisted() line: 271
SharedItemStateManager$Update.end() line: 702
SharedItemStateManager.update(ChangeLog, EventStateCollectionFactory)
line: 855
XAItemStateManager(LocalItemStateManager).update(ChangeLog) line: 326
XAItemStateManager.update(ChangeLog) line: 313
XAItemStateManager(LocalItemStateManager).update() line: 302
SessionItemStateManager.update() line: 306
NodeImpl(ItemImpl).save() line: 1214
XASessionImpl(SessionImpl).save() line: 849
The thread that just reset the overlayedState of the ItemState in the above
thread to null:
ItemState.disconnect(ItemState.java:209)
ChangeLog.modified(ChangeLog.java:70)
LocalItemStateManager.store(LocalItemStateManager.java:268)
SessionItemStateManager.store(SessionItemStateManager.java:283)
NodeImpl.makePersistent(NodeImpl.java:984)
ItemImpl.persistTransientItems(ItemImpl.java:687)
ItemImpl.save(ItemImpl.java:1198)
SessionImpl.save(SessionImpl.java:849)
The problem is that saving causes a call to disconnect of an ItemState of the
LocalItemStateManager, and that saving another session in another thread causes
a call to pull of that ItemState through the SISM notification mechanism.
> NullPointerException in ItemState
> ---------------------------------
>
> Key: JCR-1148
> URL: https://issues.apache.org/jira/browse/JCR-1148
> Project: Jackrabbit
> Issue Type: Bug
> Components: jackrabbit-core
> Affects Versions: 1.3
> Reporter: Martijn Hendriks
>
> The following happens quite regularly when multiple threads are adding,
> retrieving and removing nodes simultaneously. Looking at the code of the pull
> method, this seems due to under-synchronization somewhere as overlayedState
> was tested at line 153 for null.
> java.lang.NullPointerException
> at org.apache.jackrabbit.core.state.ItemState.pull(ItemState.java:156)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.stateModified(LocalItemStateManager.java:421)
> at
> org.apache.jackrabbit.core.state.StateChangeDispatcher.notifyStateModified(StateChangeDispatcher.java:85)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager.stateModified(SharedItemStateManager.java:434)
> at
> org.apache.jackrabbit.core.state.ItemState.notifyStateUpdated(ItemState.java:241)
> at
> org.apache.jackrabbit.core.state.ChangeLog.persisted(ChangeLog.java:271)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager$Update.end(SharedItemStateManager.java:741)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager.update(SharedItemStateManager.java:937)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:327)
> at
> org.apache.jackrabbit.core.state.XAItemStateManager.update(XAItemStateManager.java:313)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:303)
> at
> org.apache.jackrabbit.core.state.SessionItemStateManager.update(SessionItemStateManager.java:307)
> at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:1374)
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