Hi!
> On Mon, 13 Mar 2000 yodaiken@fsmlabs.com wrote:
>
> > > > Ok. Ingo: does your "low latency" patch violate this rule?
> > >
> > > yep, of course. It's a grave error to schedule during IRQ contexts, and we
> >
> > I think you mean: "of course not"!
>
> [ oops, correct :-) ]
>
> > > do have an assert in schedule() so it's plain impossible. The lowlatency
> > > patch simply works by increasing the effective frequency (occurance) of
> > > rescheduling (preemption) points [without actually rescheduling more
> > > often].
> >
> > This is too subtle for me. I don't know how you can make true
> > the first 2 things without having the third be false.
>
> well, the core of it is really simple:
>
> if (current->need_resched)
> schedule();
>
> current->need_resched is rarely set, mostly only if a process is getting
> preempted by a higher priority process. (which is the case we are
> interested in)
I tried doing something similar for fbcon, but could not. fbcon is by
far worst offender, and will happily block system for 500msec. if
(need_resched) schedule() does not work here. I tried adding
semaphores around fbcon entry points, but it does not seem to work.
(I replaced if (need_resched) schedule() with just schedule() -- I
hope that can not break anything...)
Pavel
-- The best software in life is free (not shareware)! Pavel GCM d? s-: !g p?:+ au- a--@ w+ v- C++@ UL+++ L++ N++ E++ W--- M- Y- R+- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
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