linux-kernel - Re: [PATCH 2/5] cpufreq: governor: Create separate sysfs-ops

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Message-ID: <20160203065143.GU31828@vireshk>
Date:	Wed, 3 Feb 2016 12:21:43 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Saravana Kannan <skannan@...eaurora.org>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Juri Lelli <juri.lelli@....com>,
	Rafael Wysocki <rjw@...ysocki.net>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Turquette <mturquette@...libre.com>,
	Steve Muckle <steve.muckle@...aro.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	dietmar.eggemann@....com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] cpufreq: governor: Create separate sysfs-ops

On 02-02-16, 14:21, Saravana Kannan wrote:
> I also don't like this patch because it forces governors to either implement
> their own macros and management of their attributes or force them to use the
> governor structs that come with cpufreq_governor.h. cpufreq_governor.h IMHO
> is very ondemand and conservative governor specific and is very irrelevant
> for sched-dvfs or any other governors (hint hint).

But who is stopping us from breaking that file and moving some of it
into include/linux/cpufreq.h ?

We can do that today as well, but it would be fine to do that, when we
add more governors to the core. Though, it would only take a simple
patch if people want me to do it now.

> The only time this ABBA locking is an issue is when governor are changing
> and trying to add/remove attributes. That can easily be checked in
> store_governor

store_scaling_governor ??

> and dealt with without holding the policy rwsem if the

Are you saying that we could have taken the rwsem from the generic
cpufreq.c:store() and dropped it from store_scaling_governor() ? That
would have been something similar to what I tried earlier, which I
never posted (I gave the link to that few days back).

> governors can provide their per sys and per policy attribute arrays as part
> of registering themselves.

These per-sys and per-policy attributes really suck. There is nothing
really different in the implementation, just that the show/store
callbacks have different prototype. One accept 'kboj' as the parameter,
other accept 'policy'. I would call that a HACK as well (I only
implemented it though).

That should just die. A single list of attributes is what we should
have had initially as well.

-- 
viresh