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

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

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

            oldState = state;
            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 oldState;
    }