[jboss-jira] [JBoss JIRA] Created: (JBRULES-2135) Deadlock occurs in Multithreaded Environment NamedEntryPoint lock and AbstractWorkingMemory actionQueue sync block.

Mon Jun 22 09:53:56 EDT 2009

Deadlock occurs in Multithreaded Environment NamedEntryPoint lock and AbstractWorkingMemory actionQueue sync block.
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                 Key: JBRULES-2135
                 URL: https://jira.jboss.org/jira/browse/JBRULES-2135
             Project: JBoss Drools
          Issue Type: Bug
      Security Level: Public (Everyone can see)
          Components: drools-core (fusion)
    Affects Versions: 5.0.1.FINAL
         Environment: java version "1.6.0_0"
OpenJDK Runtime Environment (IcedTea6 1.4.1) (6b14-1.4.1-0ubuntu7)
OpenJDK Client VM (build 14.0-b08, mixed mode, sharing)
            Reporter: Jonathon Leibundguth
            Assignee: Mark Proctor
            Priority: Critical

While running drools using fireUntilHalt in multithreaded environment, the following situation results in deadlock:

Thread A (Drools' Thread):  AbstractWorkingMemory method executeQueuedActions() locks actionQueue:

synchronized ( this.actionQueue )

Calls action.execute( this ) for each item in queue, in this case WorkingMemoryReteExpireAction to expire an event object.  The  WorkingMemoryReteExpireAction tries to obtain the lock in NamedEntryPoint during call to retract().

Thread B (User's Thread):  attempts to execute a NamedEntryPoint insert() action simultaneously with the above.  The thread obtains the NamedEntryPoint lock and blocks waiting for the lock on actionQueue.

Deadlock:
Thread A is blocked waiting for NamedEntryPoint lock, owned by Thread B.
Thread B is blocked waiting for lock on actionQueue, owned by Thread A.

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