I tested this exploit on a 2.6.5-gentoo-r1 kernel, and can confirm this locks your computer solid. However, when I tried it on a dual-processor box with the same kernel source, it only crashed 1 CPU.

If you have a SMP box with hangcheck timer support compiled in, perhaps you could use it to automatically reinitialise the crashed processor. Not a perfect solution, but it's better than nothing. Of course, I might've just misunderstood the purpose of the hangcheck timer and it might not offer any protection whatsoever...