linux-kernel - Re: [PATCH 2/8] cpufreq: Fix misplaced call to cpufreq_update

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Date:	Fri, 12 Jul 2013 12:36:59 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	rjw@...k.pl, toralf.foerster@....de, robert.jarzmik@...el.com,
	durgadoss.r@...el.com, tianyu.lan@...el.com,
	lantianyu1986@...il.com, dirk.brandewie@...il.com,
	stern@...land.harvard.edu, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] cpufreq: Fix misplaced call to cpufreq_update_policy()

On 12 July 2013 03:45, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> The call to cpufreq_update_policy() is placed in the CPU hotplug callback
> of cpufreq_stats, which has a higher priority than the CPU hotplug callback
> of cpufreq-core. As a result, during CPU_ONLINE/CPU_ONLINE_FROZEN, we end up
> calling cpufreq_update_policy() *before* calling cpufreq_add_dev() !
> And for uninitialized CPUs, it just returns silently, not doing anything.

Hmm..

> To add to it, cpufreq_stats is not even the right place to call
> cpufreq_update_policy() to begin with. The cpufreq core ought to handle
> this in its own callback, from an elegance/relevance perspective.
>
> So move the invocation of cpufreq_update_policy() to cpufreq_cpu_callback,
> and place it *after* cpufreq_add_dev().
>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
>  drivers/cpufreq/cpufreq.c       |    1 +
>  drivers/cpufreq/cpufreq_stats.c |    6 ------
>  2 files changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index ccc6eab..f8c3100 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1943,6 +1943,7 @@ static int __cpuinit cpufreq_cpu_callback(struct notifier_block *nfb,
>                 case CPU_ONLINE:
>                 case CPU_ONLINE_FROZEN:
>                         cpufreq_add_dev(dev, NULL);
> +                       cpufreq_update_policy(cpu);

Do we need to call this for every hotplug of cpu? I am not
talking about suspend/resume here.
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