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

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Message-ID: <be6fb99f-90bc-9ba1-b5a7-034b30734158@linaro.org>
Date:   Mon, 11 Oct 2021 17:17:08 -0400
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Cc:     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 10/7/21 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>

> ---
>   drivers/cpufreq/qcom-cpufreq-hw.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> index a2be0df7e174..0138b2ec406d 100644
> --- a/drivers/cpufreq/qcom-cpufreq-hw.c
> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> @@ -304,7 +304,8 @@ static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
>   	if (capacity > max_capacity)
>   		capacity = max_capacity;
>   
> -	arch_set_thermal_pressure(policy->cpus, max_capacity - capacity);
> +	arch_set_thermal_pressure(policy->related_cpus,
> +				  max_capacity - capacity);
>   
>   	/*
>   	 * In the unlikely case policy is unregistered do not enable
> 

-- 
Warm Regards
Thara (She/Her/Hers)