linux-kernel - Re: [PATCH v2 2/10] cpufreq: governor: Use common mutex for dbs

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Date:	Sun, 7 Feb 2016 15:01:12 +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>,
	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 v2 2/10] cpufreq: governor: Use common mutex for dbs_data
 protection

On 05-02-16, 23:59, Rafael J. Wysocki wrote:
> One more observation here.
> 
> If we are able to eliminate dbs_data_mutex from update_sampling_rate(),
> then cpufreq_governor_dbs() becomes the only user of that lock.  Further,
> if we can guarantee that the governor's ->governor callback will always
> be invoked under policy->rwsem, dbs_data_mutex becomes unnecessary and
> may be dropped.

That will be guaranteed with my 7 patches, which I will rebase and send again.

But there are cases where a single dbs_data is going to be used for multiple
policies and so relying on policy->rwsem isn't going to be sufficient.

But, yeah, we should be able to narrow down the locked area I believe.

-- 
viresh