linux-kernel - Re: [PATCH 3/5] cpufreq: qcom-cpufreq-hw: Update offline CPUs per-cpu thermal pressure

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Date:   Fri, 15 Oct 2021 13:13:47 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, sudeep.holla@....com,
        will@...nel.org, catalin.marinas@....com, linux@...linux.org.uk,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        viresh.kumar@...aro.org, amitk@...nel.org,
        daniel.lezcano@...aro.org, amit.kachhap@...il.com,
        bjorn.andersson@...aro.org, agross@...nel.org
Subject: Re: [PATCH 3/5] cpufreq: qcom-cpufreq-hw: Update offline CPUs per-cpu
 thermal pressure



On 10/11/21 10:17 PM, Thara Gopinath wrote:
> 
> 
> On 10/7/21 4:07 AM, Lukasz Luba wrote:
>> The thermal pressure signal gives information to the scheduler about
>> reduced CPU capacity due to thermal. It is based on a value stored in
>> a per-cpu 'thermal_pressure' variable. The online CPUs will get the
>> new value there, while the offline won't. Unfortunately, when the CPU
>> is back online, the value read from per-cpu variable might be wrong
>> (stale data).  This might affect the scheduler decisions, since it
>> sees the CPU capacity differently than what is actually available.
>>
>> Fix it by making sure that all online+offline CPUs would get the
>> proper value in their per-cpu variable when there is throttling
>> or throttling is removed.
>>
>> Fixes: 275157b367f479 ("cpufreq: qcom-cpufreq-hw: Add dcvs interrupt 
>> support")
>> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> 
> Thanks for the fix.
> 
> Reviewed-by: Thara Gopinath <thara.gopinath@...aro.org>
> 

Thank you for the review!