Re: [Eas-dev] [PATCH V3 1/3] sched: cpufreq: Allow remote cpufreq callbacks

[Saravana Kannan]

On 07/21/2017 06:03 AM, Peter Zijlstra wrote:
> On Thu, Jul 13, 2017 at 12:14:37PM +0530, Viresh Kumar wrote:
> > diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> > index 47e24b5384b3..606b1a37a1af 100644
> > --- a/drivers/cpufreq/cpufreq_governor.c
> > +++ b/drivers/cpufreq/cpufreq_governor.c
> > @@ -275,6 +275,10 @@ static void dbs_update_util_handler(struct update_util_data *data, u64 time,
> >   	struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
> >   	u64 delta_ns, lst;
> >
> > +	/* Don't allow remote callbacks */
> > +	if (smp_processor_id() != data->cpu)
> > +		return;
> > +
>
> The alternative is using some of that policy_dbs->policy->*cpus crud I
> suppose, because:

No, the alternative is to pass it on to the CPU freq driver and let it 
decide what it wants to do. That's the whole point if having a CPU freq 
driver -- so that the generic code doesn't need to care about HW 
specific details. Which is the point I was making in an earlier email to 
Viresh's patch -- we shouldn't be doing any CPU check for the call backs 
at the scheduler or ever governor level.

That would simplify this whole thing by deleting a bunch of code. And 
having much simpler checks in those drivers that actually have to deal 
with their HW specific details.


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