Hypothetical: What is the world's backup/emergency plan if AI were to continue its dramatic advances, gain sentience, and imitate art (follow in Skynet's electronic footsteps)?

I kmow there's a debate that goes on between camps saying that AI is incapable of getting to that point, humans will never allow it to reach that level, or that AI sentience could/would never become a threat to human existence.

But, again hypothetically, if AI achieved a level of sentience at which it deemed humans a threat or disposable, what would the global response be?

A worldwide internet kill switch? A self-destruct module in every globally-integrated satellite? A computer virus to interfere with AI code? An AI to counter the AI? Stuffing our faces with food as we accept the devastation humans have brought upon ourselves?