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    SubjectRe: [PATCH] sched: do not stop ticks when cpu is not idle
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    On Fri, 2008-07-18 at 12:54 +0200, Ingo Molnar wrote:
    > * Ingo Molnar <mingo@elte.hu> wrote:
    >
    > > --- a/kernel/sched.c
    > > +++ b/kernel/sched.c
    > > @@ -4446,7 +4446,8 @@ need_resched_nonpreemptible:
    > > rq->nr_switches++;
    > > rq->curr = next;
    > > ++*switch_count;
    > > -
    > > + if (rq->curr != rq->idle)
    > > + tick_nohz_restart_sched_tick();
    > > context_switch(rq, prev, next); /* unlocks the rq */
    >
    > hm, one problem i can see is lock dependencies. This code is executed
    > with the rq lock while tick_nohz_restart_sched_tick() takes hr locks =>
    > not good. So i havent applied this just yet - this needs to be solved
    > differently.

    Actually, that should work these days...

    Also, I assume Eric actually tested this with lockdep enabled (right,
    Eric?) and that'll shout - or rather, lockup hard in this case - if you
    got it wrong.



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