Subject: Re: [RFCv6 PATCH 03/10] sched: scheduler-driven cpu frequency
 selection
To: Leo Yan <leo.yan@linaro.org>
References: <1449641971-20827-1-git-send-email-smuckle@linaro.org>
 <1449641971-20827-4-git-send-email-smuckle@linaro.org>
 <20151216034825.GA11303@leoy-linaro>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Juri Lelli <Juri.Lelli@arm.com>,
        Patrick Bellasi <patrick.bellasi@arm.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Ricky Liang <jcliang@chromium.org>
From: Steve Muckle <steve.muckle@linaro.org>
Message-ID: <56720EE8.1090507@linaro.org>
Date: Wed, 16 Dec 2015 17:24:56 -0800
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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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