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https://issues.apache.org/jira/browse/OPENJPA-1716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12888930#action_12888930
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Rick Curtis commented on OPENJPA-1716:
--------------------------------------

I'll have to say I'm a bit apprehensive about blinding locking the BrokerImpl 
every time the StateManagerImpl needs to be locked... I posted this patch so I 
don't lose the code while I think about it. Ideally we'd be intelligent about 
locking and only lock the BrokerImpl when we need to...

> Deadlock with openjpa.Multithreaded=true
> ----------------------------------------
>
>                 Key: OPENJPA-1716
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-1716
>             Project: OpenJPA
>          Issue Type: Bug
>    Affects Versions: 2.0.0-M1, 2.0.0-M2, 2.0.0-M3, 2.0.0-beta, 2.0.0-beta2, 
> 2.0.0-beta3, 2.0.0
>            Reporter: Stefan Wokusch
>            Assignee: Rick Curtis
>         Attachments: OPENJPA-1716.PATCH
>
>
> There is a Deadlock by using Multithreaded=true and work with some Threads on 
> the same Entitymanager.
> After many hours of debugging, i found a solution for that Deadlock: The 
> Problem could be solved by adding another lock into the lock Method of the 
> StateManagerImpl:
> StateManagerImpl ~line3308
>     /**
>      * Lock the state manager if the multithreaded option is set.
>      */
>     protected void lock() {
>         if (_instanceLock != null){
>               _broker.lock();//<- This is the new Part to fix the Deadlock
>               _instanceLock.lock();
>         }
>     }
> Worked for me without Problems for a long time.
> Some other Configurations:
> <persistence xmlns="http://java.sun.com/xml/ns/persistence";
>       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; version="1.0">
>       <persistence-unit name="default" transaction-type="RESOURCE_LOCAL">
>               <mapping-file>orm.xml</mapping-file>
>               
>               <class>...</class>
>               <class>...</class>
>               
>               <properties>
>                       <property name="openjpa.OrphanedKeyAction" 
> value="log(Channel=Orphans, Level=TRACE)" />
>                       <property name="openjpa.ConnectionFactoryProperties" 
> value="PrettyPrint=true, PrettyPrintLineLength=80" />
>                       <property name="openjpa.Multithreaded" value="true" />
>                       <property name="openjpa.InverseManager" value="true" />
>                       <property name="openjpa.LockManager" value="none" />
>                       <property name="openjpa.WriteLockLevel" value="none" />
>                       <property name="openjpa.Compatibility" value="
>                                       QuotedNumbersInQueries=true, 
>                                       CopyOnDetach=true,
>                                       cascadeWithDetach=true,
>                                       
> superclassDiscriminatorStrategyByDefault=false
>                       " />
>                       <property name="openjpa.DetachState" 
> value="fetch-groups" />
>                       <property name="openjpa.jdbc.SynchronizeMappings" 
> value="buildSchema" />
>                       <!-- Default DataSource -->
>                       <property name="openjpa.ConnectionURL" 
> value="jdbc:h2:db/test" />
>                       <property name="openjpa.ConnectionDriverName" 
> value="org.h2.Driver" />
>               </properties>
>       </persistence-unit>
> </persistence>

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