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

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Message-ID: <20160204050954.GU3469@vireshk>
Date:	Thu, 4 Feb 2016 10:39:54 +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 2/11] cpufreq: governor: Use common mutex for dbs_data
 protection

On 04-02-16, 00:16, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Every governor relying on the common code in cpufreq_governor.c
> has to provide its own mutex in struct common_dbs_data.  However,
> those mutexes are never used at the same time

Why do you think so? I thought they can always be used in parallel.

Consider 2 or more policies, one can have ondemand as the governor,
whereas other one can have conservative.

If CPUs go online/offline or if governors are switching in parallel,
then cpufreq_governor_dbs() can very much run in parallel for ondemand
and conservative.

Or am I missing something here ?

-- 
viresh