linux-kernel - Re: [PATCH v2 12/12] cpufreq: governor: Narrow down the dbs_data

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Message-ID: <20160219023814.GD16983@vireshk-i7>
Date:	Fri, 19 Feb 2016 08:08:14 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 12/12] cpufreq: governor: Narrow down the
 dbs_data_mutex coverage

On 18-02-16, 18:58, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: [PATCH] cpufreq: governor: Narrow down the dbs_data_mutex coverage
> 
> Since cpufreq_governor_dbs() is now always called with policy->rwsem
> held, it cannot be executed twice in parallel for the same policy.
> Thus it is not necessary to hold dbs_data_mutex around the invocations
> of cpufreq_governor_start/stop/limits() from it as those functions
> never modify any data that can be shared between different policies.
> 
> However, cpufreq_governor_dbs() may be executed twice in parallal
> for different policies using the same gov->gdbs_data object and
> dbs_data_mutex is still necessary to protect that object against
> concurrent updates.
> 
> For this reason, narrow down the dbs_data_mutex locking to
> cpufreq_governor_init/exit() where it is needed and rename the
> mutex to gov_dbs_data_mutex to reflect its purpose.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/cpufreq/cpufreq_governor.c |   46 ++++++++++++++++++-------------------
>  1 file changed, 23 insertions(+), 23 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh