presto-main/src/main/java/io/prestosql/execution/StateMachine.java/StateMachine/compareAndSet
class StateMachine:    public boolean compareAndSet(T expectedState, T newState)
    {
        checkState(!Thread.holdsLock(lock), "Can not set state while holding the lock");
        requireNonNull(expectedState, "expectedState is null");
        requireNonNull(newState, "newState is null");

        FutureStateChange<T> futureStateChange;
        ImmutableList<StateChangeListener<T>> stateChangeListeners;
        synchronized (lock) {
            if (!state.equals(expectedState)) {
                return false;
            }

            // change to same state is not a change, and does not notify the notify listeners
            if (state.equals(newState)) {
                return false;
            }

            checkState(!isTerminalState(state), "%s can not transition from %s to %s", name, state, newState);

            state = newState;

            futureStateChange = this.futureStateChange.getAndSet(new FutureStateChange<>());
            stateChangeListeners = ImmutableList.copyOf(this.stateChangeListeners);

            // if we are now in a terminal state, free the listeners since this will be the last notification
            if (isTerminalState(state)) {
                this.stateChangeListeners.clear();
            }
        }

        fireStateChanged(newState, futureStateChange, stateChangeListeners);
        return true;
    }