linux-kernel - Re: [PATCH 2/11] cpufreq: governor: Use common mutex for dbs

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Message-ID: <CAJZ5v0g7ydctPe52=GPKCt1C9R2+Ao+T0-XA42xW1Wxv++X6gg@mail.gmail.com>
Date:	Fri, 5 Feb 2016 04:33:05 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	"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 2/11] cpufreq: governor: Use common mutex for dbs_data protection

On Fri, Feb 5, 2016 at 4:24 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 05-02-16, 04:17, Rafael J. Wysocki wrote:
>> And don't we switch governors under policy->rwsem anyway?
>
> So ? That is blocking only a single policy only, but with the new
> change, we will block all policies from doing that concurrently.

No, it won't.  Again: one lock instead of two.  How much of a
difference this makes performance-wise?

And the price is the stupid dance we need to do to even get to those
locks!  Come on.

Thanks,
Rafael