From: Jeff Dike <jdike@ka...> - 2000-05-02 16:28:24
> I would like to propose adding interrupt handling to the UM kernel.
Are you volunteering to do it, or just saying it would be a good thing?
> [ much snippage with which I agree ]
> Any comments?
Yeah. I never said that interrupts were never going to happen. They're just
something I haven't gotten around to yet. I add stuff when I miss it. And I
don't really miss real interrupts. The timer handles everything. That hurts
latency, since the timer only happens every 50ms, but you don't really notice
that too much.
That being said, my thinking on interrupts is that we should probably use
SIGIO as the hardware interrupt. I think there are some subtleties on where
SIGIO gets delivered. You'd have to make sure that it gets delivered to the
process that's currently running and not to a stopped process. There's also a
race to be careful of when input happens as a context switch is happening.
You need to make sure that SIGIO doesn't get delivered to a process that has
just been stopped. I don't think that's a big deal, you just need to be a
With SMP, we'd need to find a mechanism to round-robin the interrupts around
to the different running processes. I have no idea how that would work.
I don't think there's any magic here. It might not even be that hard to do.