Thread safety issue with GracefulShutdownHandler#decrementRequests

Given the GracefulShutdownHandler#decrementRequests function!

    private void decrementRequests() {
        long active = activeRequestsUpdater.decrementAndGet(this);
        // A
        if (shutdown) {
            synchronized (lock) {
                if (active == 0) {
                    shutdownComplete();
                }
            }
        }
    }

A thread T1 is at A. During this instant:

• A thread T2 handles a new request GracefulShutdownHandler#handleRequest
• A thread T3 shutdown the handler GracefulShutdownHandler#shutdown() but after T2 has started to handle its request (ie. after the if (shutdown) condition.

In this case even if there is an active request, T0 will call shutdownComplete()