linux-kernel - Re: [RFCv6 PATCH 03/10] sched: scheduler-driven cpu frequency selection

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Message-ID: <56720EE8.1090507@linaro.org>
Date:	Wed, 16 Dec 2015 17:24:56 -0800
From:	Steve Muckle <steve.muckle@...aro.org>
To:	Leo Yan <leo.yan@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Michael Turquette <mturquette@...libre.com>,
	Ricky Liang <jcliang@...omium.org>
Subject: Re: [RFCv6 PATCH 03/10] sched: scheduler-driven cpu frequency
 selection

Hi Leo,

On 12/15/2015 07:48 PM, Leo Yan wrote:
> I also think "set_current_state(TASK_INTERRUPTIBLE)" will introduce
> logic error when software flow run into "else" block. The reason is
> after you set state with TASK_INTERRUPTIBLE, if there have some
> scheduling happen within cpufreq_sched_try_driver_target(), then the
> thread will be remove from rq. But generally we suppose the thread
> will be on rq and can continue run after next tick.
> 
> Juri's suggestion can fix this issue. And we can use atomic_t to
> safely accessing gd->requested_freq.

I agree, it's incorrect. As I replied earlier I believe setting the task
state back to TASK_RUNNING at the top of the else block is the easiest fix.

thanks,
Steve
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