* Mike Galbraith <umgwanakikb...@gmail.com> wrote:
> On Tue, 2014-12-02 at 08:33 -0800, Linus Torvalds wrote:
>
> > Looking again at that patch (the commit message still doesn't strike
> > me as wonderfully explanatory :^) makes me worry, though.
> >
> > Is that
> >
> > if (rq->skip_clock_update-- > 0)
> > return;
> >
> > really right? If skip_clock_update was zero (normal), it now gets set
> > to -1, which has its own specific meaning (see "force clock update"
> > comment in kernel/sched/rt.c). Is that intentional? That seems insane.
>
> Yeah, it was intentional. Least lines.
>
> > Or should it be
> >
> > if (rq->skip_clock_update > 0) {
> > rq->skip_clock_update = 0;
> > return;
> > }
> >
> > or what? Maybe there was a reason the patch never got applied even to -tip.
>
> Peterz was looking at corner case proofing the thing. Saving those
> cycles has been entirely too annoying.
>
> https://lkml.org/lkml/2014/4/8/295
Hm, so that discussion died with:
https://lkml.org/lkml/2014/4/8/343
Did you ever get around to trying Peter's patch?
But ... I've yet to see rq_clock problems cause actual lockups.
That's the main problem we have with its (un)robustness and why
Peter created that rq_clock debug facility: bugs there cause
latencies but no easily actionable symptoms, which are much
harder to debug.
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
