checkHelperVersion(getClass().getClassLoader(), "AtomicReferenceFieldUpdaterAtomicHelper");
    /*
     * Since we use AtomicReferenceFieldUpdaterAtomicHelper by default, we'll "obviously" use it
     * even when Unsafe isn't available. But it's nice to have a check here to make sure that
     * nothing somehow goes wrong as the JDK restricts access to Unsafe.
     */

    // that simply loops through the subscribers and dispatches the event to each would actually
    // probably provide a stronger order guarantee, though that order would obviously be different
    // in some cases.

    /** Global event queue. */
    private final ConcurrentLinkedQueue<EventWithSubscriber> queue = new ConcurrentLinkedQueue<>();

    @Override