linux-kernel - Re: [PATCH v3 1/5] PM / devfreq: Fix cpufreq passive unregister erroring on PROBE

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Message-ID: <7f00333d-40f9-34d5-fd84-54c10d7a243d@gmail.com>
Date:   Wed, 15 Jun 2022 07:58:16 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Christian 'Ansuel' Marangi <ansuelsmth@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Sibi Sankar <sibis@...eaurora.org>,
        Saravana Kannan <skannan@...eaurora.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/5] PM / devfreq: Fix cpufreq passive unregister
 erroring on PROBE_DEFER

On 22. 6. 14. 20:06, Christian 'Ansuel' Marangi wrote:
> With the passive governor, the cpu based scaling can PROBE_DEFER due to
> the fact that CPU policy are not ready.
> The cpufreq passive unregister notifier is called both from the
> GOV_START errors and for the GOV_STOP and assume the notifier is
> successfully registred every time. With GOV_START failing it's wrong to
> loop over each possible CPU since the register path has failed for
> some CPU policy not ready. Change the logic and unregister the notifer
> based on the current allocated parent_cpu_data list to correctly handle
> errors and the governor unregister path.
> 
> Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
> Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
> ---
>  drivers/devfreq/governor_passive.c | 23 ++++++-----------------
>  1 file changed, 6 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 72c67979ebe1..0188c32f5198 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -222,8 +222,8 @@ static int cpufreq_passive_unregister_notifier(struct devfreq *devfreq)
>  {
>  	struct devfreq_passive_data *p_data
>  			= (struct devfreq_passive_data *)devfreq->data;
> -	struct devfreq_cpu_data *parent_cpu_data;
> -	int cpu, ret = 0;
> +	struct devfreq_cpu_data *parent_cpu_data, *tmp;
> +	int ret;
>  
>  	if (p_data->nb.notifier_call) {
>  		ret = cpufreq_unregister_notifier(&p_data->nb,
> @@ -232,27 +232,16 @@ static int cpufreq_passive_unregister_notifier(struct devfreq *devfreq)
>  			return ret;
>  	}
>  
> -	for_each_possible_cpu(cpu) {
> -		struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> -		if (!policy) {
> -			ret = -EINVAL;
> -			continue;
> -		}
> -
> -		parent_cpu_data = get_parent_cpu_data(p_data, policy);
> -		if (!parent_cpu_data) {
> -			cpufreq_cpu_put(policy);
> -			continue;
> -		}
> -
> +	list_for_each_entry_safe(parent_cpu_data, tmp, &p_data->cpu_data_list, node) {
>  		list_del(&parent_cpu_data->node);
> +
>  		if (parent_cpu_data->opp_table)
>  			dev_pm_opp_put_opp_table(parent_cpu_data->opp_table);
> +
>  		kfree(parent_cpu_data);
> -		cpufreq_cpu_put(policy);
>  	}

I agree this patch. Just, I'd like to make the separate function
to handle the removing of parent_cpu_data.

Please add new delete_parent_cpu_data() function under get_parent_cpu_data()
implementation and then call delete_parent_cpu_data()
in cpufreq_passive_unregister_notifier().

>  
> -	return ret;
> +	return 0;
>  }
>  
>  static int cpufreq_passive_register_notifier(struct devfreq *devfreq)


-- 
Best Regards,
Samsung Electronics
Chanwoo Choi