i wasn't clear enough what i meant by `interrupt handler'. i didn't mean
the device-specific function, but its caller. in pc/trap.c you see
if(up && !clockintr)
preempted();
and on other platforms (perhaps not enough) there are calls to preempted()
in the interrupt handler(s) that despatch the device-specific ones.
preempted calls sched, which can switch to another process before returning.--- Begin Message ---
> that's only because the clock interrupt handler directly or indirectly (eg,
> via sched) calls spllo, and other trap or interrupt handlers could do that.
wouldn't that be fatal with shared 8259 interrupts?
- erik
--- End Message ---
