linux-kernel - Re: [PATCH 3/3] cpufreq: Don't use cpu removed during cpufreq_driver

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Message-ID: <CAKohpo=Z=nA2Mr23ior8c0Qmt75+bOVLvZwNdc7OXq-+rH1dWQ@mail.gmail.com>
Date:	Fri, 4 Jan 2013 10:49:10 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	rjw@...k.pl, rafael.j.wysocki@...el.com,
	linaro-dev@...ts.linaro.org, nicolas.pitre@...aro.org,
	amit.kucheria@...aro.org, mathieu.poirier@...aro.org,
	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	pdsw-power-team@....com, linux-pm@...r.kernel.org
Subject: Re: [PATCH 3/3] cpufreq: Don't use cpu removed during cpufreq_driver_unregister

On 3 January 2013 19:55, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> I took a quick look at the problem you described above, and the cpufreq code..
> If we cannot avoid calling cpufreq_add_dev() from cpufreq_remove_dev(), then I can't
> think of anything better than what your patch does.

Good :)

> BTW, off-topic, while going through that path, I think I found a memory leak
> in __cpufreq_remove_dev():
>
>         if (unlikely(cpumask_weight(data->cpus) > 1)) {
>                 for_each_cpu(j, data->cpus) {
>                         if (j == cpu)
>                                 continue;
>                         per_cpu(cpufreq_cpu_data, j) = NULL;
>                 }
>         }
>
> We are assigning NULL without freeing that memory.

Not really. All cpus in affected_cpus (data->cpus), share the same
policy structure.
We have already taken backup of cpufreq_cpu_data for the first cpu in "data" and
are freeing it here:

	kfree(data);
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