linux-kernel - Re: [PATCH V4 5/7] cpufreq: governor: No need to manage state machine now

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Date:	Wed, 10 Feb 2016 01:36:09 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>,
	Juri Lelli <juri.lelli@....com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 5/7] cpufreq: governor: No need to manage state machine now

On Tue, Feb 9, 2016 at 4:46 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> cpufreq core now guarantees that policy->rwsem wouldn't get dropped

"The cpufreq core ..." and "won't be dropped"

> while calling CPUFREQ_GOV_POLICY_EXIT governor event and will be kept

"while running the ->governor callback for the CPUFREQ_GOV_POLICY_EXIT
event and will be held"

> acquired until the complete sequence of governor state changes has
> finished.
>
> And so we can remove the state machine checks that were put in place
> earlier.

"This allows governor state machine checks to be dropped from multiple
functions in cpufreq_governor.c."

>
> This also means that policy_dbs->policy can be initialized while

"initialized upfront"

> policy_dbs is allocated, to move all initialization together.

"so the entire initialization of struct policy_dbs is carried out in one place."

>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> Tested-by: Juri Lelli <juri.lelli@....com>
> Tested-by: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
> ---
>  drivers/cpufreq/cpufreq_governor.c | 27 +++++----------------------
>  1 file changed, 5 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index 7038ada3915d..464f346815e0 100644

[cut]

> @@ -650,14 +644,7 @@ static int cpufreq_governor_start(struct cpufreq_policy *policy)
>
>  static int cpufreq_governor_stop(struct cpufreq_policy *policy)
>  {
> -       struct policy_dbs_info *policy_dbs = policy->governor_data;
> -
> -       /* State should be equivalent to START */
> -       if (!policy_dbs->policy)
> -               return -EBUSY;
> -
> -       gov_cancel_work(policy_dbs);
> -       policy_dbs->policy = NULL;
> +       gov_cancel_work(policy);
>
>         return 0;
>  }

So maybe we can call gov_cancel_work(policy) from
cpufreq_governor_dbs() directly and get rid of this wrapper too?

Thanks,
Rafael