linux-kernel - Re: [Update PATCH 1/1] Cpufreq: Make governor data on nonboot cpus across system suspend/resume

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Date:	Fri, 15 Nov 2013 16:24:42 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lan Tianyu <tianyu.lan@...el.com>, rainer.kaluscha@....de
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Update PATCH 1/1] Cpufreq: Make governor data on nonboot cpus
 across system suspend/resume

Adding Rainer as well

On 15 November 2013 13:45, Lan Tianyu <tianyu.lan@...el.com> wrote:
> Currently, governor of nonboot cpus will be put to EXIT when system suspend.
> Since all these cpus will be unplugged and the governor usage_count decreases
> to zero. The governor data and its sysfs interfaces will be freed or released.
> This makes user config of these governors loss during suspend and resume.
>
> This doesn't happen on the governor covering boot cpu because it isn't
> unplugged during system suspend.
>
> To fix this issue, skipping governor exit during system suspend and check
> policy governor data to determine whether the governor is really needed
> to be initialized when do init. If not, return EALREADY to indicate the
> governor has been initialized and should do nothing. __cpufreq_governor()
> convert EALREADY to 0 as return value for INIT event since governor is
> still under INIT state and can do START operation.

Though the patch I have sent fixes a problem similar to this but I don't think
patch of any of us will solve the issue Rainer is facing..

I checked his system configuration and its like this:
- Four CPUs, all having separate clock domains (atleast from kernel
perspective) and so separate policy structure.
- All are using ondemand governor
- not using CPUFREQ_HAVE_GOVERNOR_PER_POLICY feature
- So there is a single set of tunables for ondemand governor that is applicable
across all CPUs..

The way INIT/EXIT are designed in cpufreq_governor.c should take care
of this scenario.

memory for tunables must not be freed unless all the CPUs are removed.
Which can't happen, as we only offline non-boot CPUs and so I believe
that memory isn't getting freed and so your solution wouldn't address his
problem..

Sorry if I said something stupid enough :)

--
viresh
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