[jboss-jira] [JBoss JIRA] (WFLY-5596) MessageDrivenComponent startDelivery/stopDelivery is not thread safe

[James Livingston (JIRA)]

James Livingston created WFLY-5596:
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             Summary: MessageDrivenComponent startDelivery/stopDelivery is not thread safe
                 Key: WFLY-5596
                 URL: https://issues.jboss.org/browse/WFLY-5596
             Project: WildFly
          Issue Type: Bug
          Components: EJB, JMS
    Affects Versions: 10.0.0.CR4
            Reporter: James Livingston
            Assignee: Jeff Mesnil


WFLY-4470 made a change to prevent MDBs being activated or deactivated multiple times, but it is not thread safe. A volatile boolean is used for the flag, but there is no protection against multiple threads invoking the methods simultaneously.

Possible effects include:
* activating the endpoint twice, with (probably) only one deactivation later, leading to not de-registering XA resources from the recovery manager properly
* activate() and deactivate() running in the wrong order if done by separate threads

Several simple solutions probably will not work correctly. Using an AtomicBoolean would stop multiple activations/deactivations from concurrent calls, but would mean that startDelivery() could return before the activation was one. Using a synchronized block or other exclusive lock would work, however since it involves invoking non-container code (the resource adapter), there could potentially be a deadlock risk if that invoked some related container functionality.



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