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https://issues.apache.org/jira/browse/JCR-672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12481921
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Jukka Zitting commented on JCR-672:
-----------------------------------
> Is there anything a non-Jackrabbit-developer can do to help?
I'm afraid there's relatively little to do. Reporting all known deadlock
occurrences with as much detail as possible would help, but in the end someone
needs to bite the bullet and start rethinking the locking behaviour within
jackrabbit-core.
Some people have workarounds that explicitly synchronize all the versioning
operations of concurrent sessions. Documenting such a workaround with example
code on the Jackrabbit wiki would be appreciated, but of course it's still just
a workaround.
> Deadlock on concurrent save/checkin operations possible
> -------------------------------------------------------
>
> Key: JCR-672
> URL: https://issues.apache.org/jira/browse/JCR-672
> Project: Jackrabbit
> Issue Type: Bug
> Components: versioning
> Reporter: Przemo Pakulski
>
> Save and checkin operations are trying to acquire 2 locks in different order,
> what leads to deadlock.
> ->save
> 1.SharedItemStateManager.acquireWriteLock
> 2.AbstractVersionManager.acquireWriteLock -> locked
> ->checkin
> 1.AbstractVersionManager.acquireWriteLock
> 2.SharedItemStateManager.acquireReadLock -> locked
> "Thread-4" prio=6 tid=0x0312d840 nid=0x824 in Object.wait()
> [0x03cef000..0x03cefa68]
> at java.lang.Object.wait(Native Method)
> - waiting on <0x23210968> (a
> EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock$WriterLock)
> at java.lang.Object.wait(Unknown Source)
> at
> EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock$WriterLock.acquire(Unknown
> Source)
> - locked <0x23210968> (a
> EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock$WriterLock)
> at
> org.apache.jackrabbit.core.version.AbstractVersionManager.acquireWriteLock(AbstractVersionManager.java:124)
> at
> org.apache.jackrabbit.core.version.VersionManagerImpl.setNodeReferences(VersionManagerImpl.java:413)
> at
> org.apache.jackrabbit.core.version.VersionItemStateProvider.setNodeReferences(VersionItemStateProvider.java:125)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager$Update.end(SharedItemStateManager.java:699)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager.update(SharedItemStateManager.java:810)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:326)
> at
> org.apache.jackrabbit.core.state.XAItemStateManager.update(XAItemStateManager.java:313)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:302)
> at
> org.apache.jackrabbit.core.state.SessionItemStateManager.update(SessionItemStateManager.java:295)
> at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:1204)
> - locked <0x2332eaa0> (a org.apache.jackrabbit.core.XASessionImpl)
> at JrTestDeadlock.run(JrTestDeadlock.java:87)
> "Thread-3" prio=6 tid=0x0312db18 nid=0xa04 in Object.wait()
> [0x03caf000..0x03cafae8]
> at java.lang.Object.wait(Native Method)
> - waiting on <0x232d1360> (a
> EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock$ReaderLock)
> at java.lang.Object.wait(Unknown Source)
> at
> EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock$ReaderLock.acquire(Unknown
> Source)
> - locked <0x232d1360> (a
> EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock$ReaderLock)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager.acquireReadLock(SharedItemStateManager.java:1361)
> at
> org.apache.jackrabbit.core.state.SharedItemStateManager.hasItemState(SharedItemStateManager.java:270)
> at
> org.apache.jackrabbit.core.state.LocalItemStateManager.hasItemState(LocalItemStateManager.java:180)
> at
> org.apache.jackrabbit.core.state.XAItemStateManager.hasItemState(XAItemStateManager.java:252)
> at
> org.apache.jackrabbit.core.state.SessionItemStateManager.hasItemState(SessionItemStateManager.java:188)
> at
> org.apache.jackrabbit.core.ItemManager.itemExists(ItemManager.java:256)
> at org.apache.jackrabbit.core.NodeImpl.hasProperty(NodeImpl.java:1509)
> at
> org.apache.jackrabbit.core.version.InternalFrozenNodeImpl.checkin(InternalFrozenNodeImpl.java:276)
> at
> org.apache.jackrabbit.core.version.InternalFrozenNodeImpl.checkin(InternalFrozenNodeImpl.java:248)
> at
> org.apache.jackrabbit.core.version.InternalVersionHistoryImpl.checkin(InternalVersionHistoryImpl.java:440)
> at
> org.apache.jackrabbit.core.version.AbstractVersionManager.checkin(AbstractVersionManager.java:397)
> at
> org.apache.jackrabbit.core.version.VersionManagerImpl$2.run(VersionManagerImpl.java:289)
> at
> org.apache.jackrabbit.core.version.VersionManagerImpl$DynamicESCFactory.doSourced(VersionManagerImpl.java:611)
> - locked <0x2320c5d8> (a
> org.apache.jackrabbit.core.version.VersionManagerImpl$DynamicESCFactory)
> at
> org.apache.jackrabbit.core.version.VersionManagerImpl.checkin(VersionManagerImpl.java:285)
> at
> org.apache.jackrabbit.core.version.XAVersionManager.checkin(XAVersionManager.java:161)
> at org.apache.jackrabbit.core.NodeImpl.checkin(NodeImpl.java:2944)
> at JrTestDeadlock.run(JrTestDeadlock.java:103)
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