linux-kernel - Re: [PATCH v3 5/5] thermal: cpu_cooling: update the cpu device when cpufreq updates the policy cpu

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Date:	Tue, 3 Mar 2015 18:37:21 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Kapileshwar Singh <kapileshwar.singh@....com>
Cc:	Javi Merino <Javi.Merino@....com>,
	Eduardo Valentin <edubezval@...il.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Punit Agrawal <Punit.Agrawal@....com>,
	Lina Iyer <lina.iyer@...aro.org>,
	Mark Brown <broonie@...nel.org>, Jon Medhurst <tixy@...aro.org>
Subject: Re: [PATCH v3 5/5] thermal: cpu_cooling: update the cpu device when
 cpufreq updates the policy cpu

On 3 March 2015 at 17:11, Kapileshwar Singh <kapileshwar.singh@....com> wrote:
> Yes I indeed tested the case where we cache the device pointer of the CPU for which the OPP's are populated.
> When this CPU is hotplugged out, it invalidates the device pointer itself. Here are the error we get in dmesg:

What do you mean by 'invalidates the device pointer' ? that cpu_dev is NULL ?

> <3>[67203.216774] opp_get_voltage: Invalid parameters
> <3>[67203.326774] opp_get_voltage: Invalid parameters
> <3>[67203.326774] opp_get_voltage: Invalid parameters

Have you handwritten them ? Why don't they precede with dev_pm_* ??

>
> Which happens because:
>
> unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
> {
> ..
>         tmp_opp = rcu_dereference(opp);
>         if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
>                 pr_err("%s: Invalid parameters\n", __func__);

This %s should print routine name ..

>         else
> ..
>
> Which happens when
>
>         opp = dev_pm_opp_find_freq_exact(cpufreq_device->cpu_dev, freq_hz,
>                                          true);
>
> returns a an erroneous or NULL OPP or the opp is unavailable (in the above condition)

Please goto the depth of this thing, as I don't think it should happen.

Over that I was asking you if you have tested the solution Javi gave,
because OPPs
wouldn't have been initialized for other CPUs once policy->cpu goes down.
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