linux-kernel - Re: [PATCH 3/11] cpufreq: governor: Use common global_dbs

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Date:	Thu, 4 Feb 2016 17:52:46 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Juri Lelli <juri.lelli@....com>,
	Steve Muckle <steve.muckle@...aro.org>,
	Saravana Kannan <skannan@...eaurora.org>
Subject: Re: [PATCH 3/11] cpufreq: governor: Use common global_dbs_data pointer

On Thu, Feb 4, 2016 at 6:36 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 04-02-16, 00:22, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> If the ondemand and conservative governors cannot use per-policy
>> tunables (CPUFREQ_HAVE_GOVERNOR_PER_POLICY is not set in the cpufreq
>> driver), all policy objects point to the same single dbs_data object.
>> Additionally, that object is pointed to by a global pointer hidden in
>> the governor's data structures.
>>
>> There is no reason for that pointer to be buried in those
>> data structures, though, so make it explicitly global.
>>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
>> Index: linux-pm/drivers/cpufreq/cpufreq_governor.c
>> ===================================================================
>> --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c
>> +++ linux-pm/drivers/cpufreq/cpufreq_governor.c
>> @@ -22,6 +22,9 @@
>>
>>  #include "cpufreq_governor.h"
>>
>> +struct dbs_data *global_dbs_data;
>> +EXPORT_SYMBOL_GPL(global_dbs_data);
>
> Oh man, please save me from Rafael's Rant :)
>
> I think, this is simply wrong.
>
> Believe me its very difficult for me to say this to you :). You are
> way better than me, and I am sure that I haven't understood cupfreq
> after so many years :)
>
> Consider a two policy system, who is stopping us from setting ondemand
> for one of them and conservative for the other one ? And so, we will
> have two gdbs_data ..

I don't really regard that as an entirely sane thing to do, but you
have a point here.

> Sorry for the noise, if I am being utterly stupid :(

No, that's something I have overlooked, sorry about that.

Well, I'll need to go back to this patch or maybe drop it even.

Thanks,
Rafael