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Date:   Tue, 9 Feb 2021 16:41:23 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Yue Hu <zbestahu@gmail.com>
Cc:     rjw@rjwysocki.net, rafael.j.wysocki@intel.com, mingo@redhat.com,
        peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, huyue2@yulong.com, zbestahu@163.com,
        zhangwen@yulong.com
Subject: Re: [PATCH] cpufreq: schedutil: Don't use the limits_changed flag
 any more
Message-ID: <20210209111123.kzx36ghdac4rpfuh@vireshk-i7>
References: <20210208030723.781-1-zbestahu@gmail.com>
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On 08-02-21, 11:07, Yue Hu wrote:
> From: Yue Hu <huyue2@yulong.com>
> 
> The limits_changed flag was introduced by commit 600f5badb78c
> ("cpufreq: schedutil: Don't skip freq update when limits change") due
> to race condition where need_freq_update is cleared in get_next_freq()
> which causes reducing the CPU frequency is ineffective while busy.
> 
> But now, the race condition above is gone because get_next_freq()
> doesn't clear the flag any more after commit 23a881852f3e ("cpufreq:
> schedutil: Don't skip freq update if need_freq_update is set").
> 
> Moreover, need_freq_update currently will be set to true only in
> sugov_should_update_freq() if CPUFREQ_NEED_UPDATE_LIMITS is not set
> for the driver. However, limits may have changed at any time. And
> subsequent frequence update is depending on need_freq_update. So, we
> may skip this update.
> 
> Hence, let's remove it to avoid above issue and make code more simple.
> 
> Signed-off-by: Yue Hu <huyue2@yulong.com>
> ---
>  kernel/sched/cpufreq_schedutil.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh