linux-kernel - Re: [PATCH] thermal/cpufreq: increment i in cpufreq_get_requested

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Date: Mon, 6 May 2024 10:41:52 +0100
From: Lukasz Luba <lukasz.luba@....com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Amit Daniel Kachhap <amit.kachhap@...il.com>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Viresh Kumar <viresh.kumar@...aro.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] thermal/cpufreq: increment i in
 cpufreq_get_requested_power()

Hi Dan,

On 5/4/24 12:25, Dan Carpenter wrote:
> We accidentally deleted the "i++" as part of a cleanup.  Restore it.
> 
> Fixes: 3f7ced7ac9af ("drivers/thermal/cpufreq_cooling : Refactor thermal_power_cpu_get_power tracing")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> This is based on static analysis and not tested.

Thank you for the patch. I have analyzed the code and why it
haven't trigger an issue when I was testing it.

I looks like the function get_load() which is called above that 'i++'
and takes the 'i' as the last argument is compiled in 2 versions:
1. for SMP system and the last argument 'cpu_idx' is ignored
2. for !SMP where we use the last argument 'cpu_idx' which is 'i'
value. Although, for !SMP system we only have 1 cpu, thus the
initialized 'int i = 0' at the beginning of that
cpufreq_get_requested_power() is used correctly.
The loop for !SMP goes only once.

> 
>   drivers/thermal/cpufreq_cooling.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
> index 280071be30b1..a074192896de 100644
> --- a/drivers/thermal/cpufreq_cooling.c
> +++ b/drivers/thermal/cpufreq_cooling.c
> @@ -249,6 +249,7 @@ static int cpufreq_get_requested_power(struct thermal_cooling_device *cdev,
>   			load = 0;
>   
>   		total_load += load;
> +		i++;
>   	}
>   
>   	cpufreq_cdev->last_load = total_load;

Would you agree that I will keep you as 'Reported-by' and send a
separate patch to change that !SMP code completely in that
get_load() function and get rid of the 'cpu_idx' argument?
Or I'm happy that you can develop such code and I can review it.
It's up to you.

Regards,
Lukasz