linux-kernel - Re: [PATCH v3] cpufreq: ondemand: handle SW coordinated CPUs

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Message-ID: <7225350.Xenu33kWOn@vostro.rjw.lan>
Date:	Thu, 22 Nov 2012 22:27:10 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Fabio Baltieri <fabio.baltieri@...aro.org>
Cc:	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	Rickard Andersson <rickard.andersson@...ricsson.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] cpufreq: ondemand: handle SW coordinated CPUs

On Thursday, November 22, 2012 06:02:37 PM Fabio Baltieri wrote:
> Hello Rafael,
> 
> thanks for the review!  I only have one concern before sending a v4:
> 
> On Thu, Nov 22, 2012 at 01:10:15AM +0100, Rafael J. Wysocki wrote:
> > > @@ -627,32 +659,41 @@ static void do_dbs_timer(struct work_struct *work)
> > >  				delay -= jiffies % delay;
> > >  		}
> > >  	} else {
> > > -		__cpufreq_driver_target(dbs_info->cur_policy,
> > > -			dbs_info->freq_lo, CPUFREQ_RELATION_H);
> > > +		if (sample)
> > > +			__cpufreq_driver_target(dbs_info->cur_policy,
> > > +						dbs_info->freq_lo,
> > > +						CPUFREQ_RELATION_H);
> > >  		delay = dbs_info->freq_lo_jiffies;
> > >  	}
> > > -	schedule_delayed_work_on(cpu, &dbs_info->work, delay);
> > > +	schedule_delayed_work_on(smp_processor_id(), dw, delay);
> > 
> > We're not supposed to be using smp_processor_id() any more.
> > get_cpu()/put_cpu() should be used instead.
> 
> That's going to add preemption protection, do I need that?  The function
> is called from a kworker with the affinity set on a specific CPU, so it
> should not migrate to a different one during execution.

Yes, you're right, in that case it should be OK.

> I agree with you for all the other comments.

Cool. :-)

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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