Two interrupts can run at the same time even under UP ("same time" in a
very limited sense, obviously - but one interrupt can interrupt the
other). As such, if we are ever in a critical section where this makes a
difference, that critical section obviously has to do a cli/sti.
And they do.
> In any event, I think that the rtlinux soft-interrupts fits into this
> scheme quite well and should make the irq_lock unecessary.
I don't believe you can make the irq_lock unnecessary - _something_ like
that is needed anyway.
Linus