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https://issues.apache.org/jira/browse/DERBY-4129?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Knut Anders Hatlen updated DERBY-4129:
--------------------------------------
Attachment: BlobDeadlock.java
threaddump.txt
I am able to reproduce this deadlock. See the attached files BlobDeadlock.java
and threaddump.txt.
Note that the repro has two threads performing queries using the same
Connection object. As far as I can see, that's the only way two threads can end
up accessing the same BaseContainerHandle, and thereby running into this
deadlock. Having concurrent threads using the same Connection object is not
recommended, but it should of course not cause a Java-level deadlock.
Normally, deadlock between threads sharing the same Connection is prevented by
only allowing one thread at a time to enter the engine through a single
Connection. For instance, EmbedResultSet.next() and EmbedResultSet.close() will
synchronize on the parent EmbedConnection object before calling the engine
code. The getters don't synchronize on the EmbedConnection because they just
return a value that was cached in the ResultSet when next() was called.
The reason why this doesn't work as intended in this case, is that
EmbedResultSet.getBytes() will have to go to the store to fetch the value if
the BLOB column is larger than what EmbedResultSet.next() will cache
(basically, it doesn't fit on one page). But since the getters don't
synchronize on the EmbedConnection, we now enter the engine without making sure
that no other thread is actively using the same connection. If getBytes() had
synchronized on the connection, we would have been stopped from entering the
engine much earlier because the other thread involved in the deadlock enters
the engine from close(), where it does synchronize on the connection, and we
wouldn't run into the deadlock.
> Deadlock
> --------
>
> Key: DERBY-4129
> URL: https://issues.apache.org/jira/browse/DERBY-4129
> Project: Derby
> Issue Type: Bug
> Affects Versions: 10.4.2.0
> Environment: Linux 2.6.18-53.1.14.el5 #1 SMP Wed Mar 5 11:36:49 EST
> 2008 i686 i686 i386 GNU/Linux
> Reporter: Malchenko Inna
> Attachments: BlobDeadlock.java, threaddump.txt
>
>
> Threads working with embedded derby get deadlocked.
> Thread dump:
> Found one Java-level deadlock:
> =============================
> "http-8080-13":
> waiting to lock monitor 0x09d1a37c (object 0x9560fcd8, a
> org.apache.derby.impl.store.raw.data.BaseContainerHandle),
> which is held by "dwc.ma.MAJobsManager:dwc.ma.MAManager"
> "dwc.ma.MAJobsManager:dwc.ma.MAManager":
> waiting to lock monitor 0x09d1a57c (object 0x93da0180, a
> org.apache.derby.impl.store.raw.data.StoredPage),
> which is held by "http-8080-13"
> Java stack information for the threads listed above:
> ===================================================
> "http-8080-13":
> at java.util.Observable.deleteObserver(Observable.java:78)
> - waiting to lock <0x9560fcd8> (a
> org.apache.derby.impl.store.raw.data.BaseContainerHandle)
> at
> org.apache.derby.impl.store.raw.data.BasePage.releaseExclusive(Unknown Source)
> - locked <0x93da0180> (a
> org.apache.derby.impl.store.raw.data.StoredPage)
> at
> org.apache.derby.impl.store.raw.data.CachedPage.releaseExclusive(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.StoredPage.releaseExclusive(Unknown
> Source)
> at org.apache.derby.impl.store.raw.data.BasePage.unlatch(Unknown Source)
> at
> org.apache.derby.impl.store.raw.data.OverflowInputStream.fillByteHolder(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.BufferedByteHolderInputStream.read(Unknown
> Source)
> at java.io.DataInputStream.readFully(DataInputStream.java:176)
> at java.io.DataInputStream.readFully(DataInputStream.java:152)
> at org.apache.derby.iapi.types.SQLBinary.readExternal(Unknown Source)
> at org.apache.derby.iapi.types.SQLBinary.getValue(Unknown Source)
> at org.apache.derby.iapi.types.SQLBinary.getBytes(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedResultSet.getBytes(Unknown Source)
> at dwc.ma.MAOrderProcessor.loadData(MAOrderProcessor.java:147)
> - locked <0x91f211b0> (a java.lang.Object)
> - locked <0x91f6a068> (a dwc.ma.MAOrderProcessor)
> at
> dwc.ma.MAOrderProcessor.generateBundlesForUser(MAOrderProcessor.java:538)
> - locked <0x91f6a068> (a dwc.ma.MAOrderProcessor)
> at
> dwc.ma.MARequestProcessor$HBundleRequest.process(MARequestProcessor.java:239)
> at dwc.ma.MARequestProcessor.processRequest(MARequestProcessor.java:39)
> at dwc.ma.doProc.doPost(doProc.java:92)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
> at
> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
> at
> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
> at
> org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:738)
> at
> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
> at
> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
> at
> org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
> at
> org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
> at
> org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
> at
> org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
> at
> org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
> at
> org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
> at
> org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
> at
> org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
> at
> org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
> at java.lang.Thread.run(Thread.java:595)
> "dwc.ma.MAJobsManager:dwc.ma.MAManager":
> at
> org.apache.derby.impl.store.raw.data.BasePage.releaseExclusive(Unknown Source)
> - waiting to lock <0x93da0180> (a
> org.apache.derby.impl.store.raw.data.StoredPage)
> at
> org.apache.derby.impl.store.raw.data.CachedPage.releaseExclusive(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.StoredPage.releaseExclusive(Unknown
> Source)
> at org.apache.derby.impl.store.raw.data.BasePage.update(Unknown Source)
> at java.util.Observable.notifyObservers(Observable.java:142)
> at java.util.Observable.notifyObservers(Observable.java:98)
> at
> org.apache.derby.impl.store.raw.data.BaseContainerHandle.informObservers(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.BaseContainerHandle.close(Unknown Source)
> - locked <0x9560fcd8> (a
> org.apache.derby.impl.store.raw.data.BaseContainerHandle)
> at
> org.apache.derby.impl.store.access.conglomerate.OpenConglomerate.close(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.conglomerate.GenericController.close(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.conglomerate.GenericConglomerateController.closeForEndTransaction(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.RAMTransaction.closeControllers(Unknown
> Source)
> at org.apache.derby.impl.store.access.RAMTransaction.commit(Unknown
> Source)
> at
> org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.doCommit(Unknown
> Source)
> at
> org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.userCommit(Unknown
> Source)
> at org.apache.derby.impl.jdbc.TransactionResourceImpl.commit(Unknown
> Source)
> at
> org.apache.derby.impl.jdbc.EmbedConnection.commitIfAutoCommit(Unknown Source)
> at
> org.apache.derby.impl.jdbc.ConnectionChild.commitIfAutoCommit(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.resultSetClosing(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedResultSet.close(Unknown Source)
> - locked <0x91f0b7d0> (a org.apache.derby.impl.jdbc.EmbedConnection30)
> at
> dwc.ma.MAStatsProcessor$UserStatsBundlesProc.run(MAStatsProcessor.java:117)
> at dwc.ma.MAJobsManager$Runner.run(MAJobsManager.java:84)
> - locked <0x91fce338> (a java.util.LinkedList)
> at java.lang.Thread.run(Thread.java:595)
> Found 1 deadlock.
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