On Sun, Oct 11, 2015 at 08:12:39PM +0200, Thomas Gleixner wrote:
> On Mon, 28 Sep 2015, Yunhong Jiang wrote:
> > static void internal_add_timer(struct tvec_base *base, struct timer_list
> > *timer)
> > {
> > + bool kick_nohz = false;
> > +
> > /* Advance base->jiffies, if the base is empty */
> > if (!base->all_timers++)
> > base->timer_jiffies = jiffies;
> > @@ -424,9 +426,17 @@ static void internal_add_timer(struct tvec_base *base,
> > struct timer_list *timer)
> > */
> > if (!(timer->flags & TIMER_DEFERRABLE)) {
> > if (!base->active_timers++ ||
> > - time_before(timer->expires, base->next_timer))
> > + time_before(timer->expires, base->next_timer)) {
> > base->next_timer = timer->expires;
> > - }
> > + /*
> > + * CPU in dynticks need reevaluate the timer wheel
> > + * if newer timer added with next_timer updated.
> > + */
> > + if (base->nohz_active)
> > + kick_nohz = true;
> > + }
> > + } else if (base->nohz_active && tick_nohz_full_cpu(base->cpu))
> > + kick_nohz = true;
>
> Why do you want to kick the other cpu when a deferrable timer got added?
This is what happens in current implementation and this patch does not
change the logic. According to the comments, it's to avoid race with
idle_cpu(). Frankly speaking, I didn't get the idea of the race.
Viresh, do you have any hints?
Thanks
--jyh
>
> Thanks,
>
> tglx
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
