NMI handler

Trying to register a NMI handler in the kernel created a lot of kernel crashes.

Oprofile does low level kernel hacks to install there nmi handler.

I found there was a recent patch that reverted an easy to use NMI register function: http://lkml.indiana.edu/hypermail/linux/kernel/0605.1/0524.html

So I reverted some of the code form the patch to register my own.

______________

Looking into the oprofile code, I decided to not do what I orginally posted.

I went ahead and ported the oprofile NMI handler over. It does a low level memory operation to switch out the kernels NMI handler with its own. This way the response time to receive the interrupt is minimized.