Re: [tip:sched/urgent] Sched: fix skip_clock_update optimization

From: Peter Zijlstra
Date: Thu Dec 09 2010 - 10:33:14 EST


On Wed, 2010-12-08 at 20:40 +0000, tip-bot for Mike Galbraith wrote:
> @@ -4063,6 +4062,8 @@ need_resched_nonpreemptible:
>
> put_prev_task(rq, prev);
> next = pick_next_task(rq);
> + clear_tsk_need_resched(prev);
> + rq->skip_clock_update = 0;
>
> if (likely(prev != next)) {
> sched_info_switch(prev, next);
> @@ -4071,6 +4072,7 @@ need_resched_nonpreemptible:
> rq->nr_switches++;
> rq->curr = next;
> ++*switch_count;
> + WARN_ON_ONCE(test_tsk_need_resched(next));

I just managed to trigger this one.. will try and reproduce to find out
wth happened.
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