linux-kernel - Re: [PATCH 1/2] cpufreq: Add governor operation ongoing flag

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Date:	Wed, 14 Aug 2013 10:51:47 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Xiaoguang Chen <chenxg@...vell.com>
Cc:	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Xiaoguang Chen <chenxg.marvell@...il.com>
Subject: Re: [PATCH 1/2] cpufreq: Add governor operation ongoing flag

On 13 August 2013 12:39, Xiaoguang Chen <chenxg@...vell.com> wrote:
> __cpufreq_governor operation needs to be executed one by one.
> If one operation is ongoing, the other operation can't be executed.
> If the order is not guaranteed, there may be unexpected behavior.

What order??

>  For example, governor is in enable state, and one process
> tries to stop the goveror, but it is scheduled out before policy->
> governor->governor() is executed, but the governor enable flag is
> set to false already. Then one other process tries to start governor,
> It finds enable flag is false, and it can process down to do governor
> start operation, So the governor is started twice.

That's not possible. A process will not and should not call START
before calling STOP. And so the order of calling these routines must
be forced.

Hence, we may not need your patch.
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