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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5632) Logical deadlock happened when freezing/unfreezing the database
Date Thu, 14 Mar 2013 15:10:13 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13602328#comment-13602328

Knut Anders Hatlen commented on DERBY-5632:

I agree that only allowing unfreeze from the connection that froze the database would be limiting.
Are you saying that the deadlocks involve different kinds of objects in the single-connection
case than in the multiple-connection case, and that the committed fix would only have effect
on the single-connection case?
> Logical deadlock happened when freezing/unfreezing the database
> ---------------------------------------------------------------
>                 Key: DERBY-5632
>                 URL: https://issues.apache.org/jira/browse/DERBY-5632
>             Project: Derby
>          Issue Type: Bug
>          Components: Documentation, Services
>    Affects Versions:
>         Environment: Oracle M3000/Solaris 10
>            Reporter: Brett Bergquist
>            Assignee: Knut Anders Hatlen
>              Labels: derby_triage10_10
>             Fix For:
>         Attachments: experimental-v1.diff, experimental-v2.diff, stack.txt
> Tried to make a quick database backup by freezing the database, performing a ZFS snapshot,
and then unfreezing the database.   The database was frozen but then a connection to the database
could not be established to unfreeze the database.
> Looking at the stack trace of the network server, , I see 3 threads that are trying to
process a connection request.   Each of these is waiting on:
>                 at org.apache.derby.impl.store.access.RAMAccessManager.conglomCacheFind(Unknown
>                 - waiting to lock <0xfffffffd3a7fcc68> (a org.apache.derby.impl.services.cache.ConcurrentCache)
> That object is owned by:
>                 - locked <0xfffffffd3a7fcc68> (a org.apache.derby.impl.services.cache.ConcurrentCache)
>                 at org.apache.derby.impl.store.access.RAMTransaction.findExistingConglomerate(Unknown
>                 at org.apache.derby.impl.store.access.RAMTransaction.openGroupFetchScan(Unknown
>                 at org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.updateIndexStatsMinion(Unknown
>                 at org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.runExplicitly(Unknown
>                 at org.apache.derby.impl.sql.execute.AlterTableConstantAction.updateStatistics(Unknown
> which itself is waiting for the object:
>                 at java.lang.Object.wait(Native Method)
>                 - waiting on <0xfffffffd3ac1d608> (a org.apache.derby.impl.store.raw.log.LogToFile)
>                 at java.lang.Object.wait(Object.java:485)
>                 at org.apache.derby.impl.store.raw.log.LogToFile.flush(Unknown Source)
>                 - locked <0xfffffffd3ac1d608> (a org.apache.derby.impl.store.raw.log.LogToFile)
>                 at org.apache.derby.impl.store.raw.log.LogToFile.flush(Unknown Source)
>                 at org.apache.derby.impl.store.raw.data.BaseDataFileFactory.flush(Unknown
> So basically what I think is happening is that the database is frozen, the statistics
are being updated on another thread which has the "org.apache.derby.impl.services.cache.ConcurrentCache"
locked and then waits for the LogToFile lock and the connecting threads are waiting to lock
"org.apache.derby.impl.services.cache.ConcurrentCache" to connect and these are where the
database is going to be unfrozen.    Not a deadlock as far as the JVM is concerned but it
will never leave this state either.

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