Wait, I just realized something: currently, the kernel lock is
only taken once for a chain of shared interrupts. This way,
it will be taken for each individual call.

I'm not sure if I like that.. though with MP-safe interrupt handlers,
we'd need this construct anyway.. Hm.

Then again, for MP system with ioapics, the chance of shared interrupts
is a lot smaller.

Well, I'm not sure. Do you have an MP system with a shared interrupt
line you can test on?

- Frank