On Wed, 13 Mar 2013, Lorenzo Pieralisi wrote:
> > + /* Take care of enforced broadcast requests */
> > + cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
> > + cpumask_clear(tick_broadcast_force_mask);
>
> I tested the set and it works fine on a dual cluster big.LITTLE testchip
> using broadcast timer to manage deep idle cluster states.
>
> Just asking a question: the force mask is cleared before sending the
> timer IPI. Would not be better to clear it after the IPI is sent in
>
> tick_do_broadcast(...) ?
>
> Can you spot a regression if we do this ? The idle thread checks that
> mask with irqs disabled, so it is possible that we clear the mask before
> the CPU has a chance to get the IPI. If we clear the mask after sending
> the IPI, we are increasing the chances for the idle thread to get it.
>
> It is just a further optimization, just asking, thanks.
Need to think about that.
> > @@ -524,7 +530,16 @@ void tick_broadcast_oneshot_control(unsi
> > WARN_ON_ONCE(cpumask_test_cpu(cpu,
> > tick_broadcast_pending_mask));
> > if (!cpumask_test_and_set_cpu(cpu,
> > tick_broadcast_oneshot_mask)) {
> > clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
> > - if (dev->next_event.tv64 < bc->next_event.tv64)
> > + /*
> > + * We only reprogram the broadcast timer if we
> > + * did not mark ourself in the force mask and
> > + * if the cpu local event is earlier than the
> > + * broadcast event. If the current CPU is in
> > + * the force mask, then we are going to be
> > + * woken by the IPI right away.
> > + */
> > + if (!cpumask_test_cpu(cpu, tick_broadcast_force_mask) &&
> Is the test against tick_broadcast_force_mask necessary if we add the check
> in the idle thread before entering idle ? It does not hurt, agreed, and we'd
> better leave it there, it is just for my own understanding, thanks a lot.
Well, it's necessary for all archs which do not have the check (yet).
> Having said that, on the series:
>
> Tested-by: Lorenzo Pieralisi <lorenzo.pieral...@arm.com>
Thanks,
tglx
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