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.