linux-kernel - Re: [PATCH v4 1/4] PM / devfreq: Fix cpufreq passive unregister erroring on PROBE

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Message-ID: <17cb21c6-317a-3f70-8c4d-4d8fe20604d4@gmail.com>
Date:   Wed, 15 Jun 2022 15:48:03 +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 v4 1/4] PM / devfreq: Fix cpufreq passive unregister
 erroring on PROBE_DEFER

On 22. 6. 15. 08:09, 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 | 39 +++++++++++++-----------------
>  1 file changed, 17 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 72c67979ebe1..95de336f20d5 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -34,6 +34,20 @@ get_parent_cpu_data(struct devfreq_passive_data *p_data,
>  	return NULL;
>  }
>  
> +static void delete_parent_cpu_data(struct devfreq_passive_data *p_data)
> +{
> +	struct devfreq_cpu_data *parent_cpu_data, *tmp;
> +

Need to add the validation checking of argument as following:

	if (!p_data)
		return;

> +	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);
> +	}
> +}
> +
>  static unsigned long get_target_freq_by_required_opp(struct device *p_dev,
>  						struct opp_table *p_opp_table,
>  						struct opp_table *opp_table,
> @@ -222,8 +236,7 @@ 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;
> +	int ret;
>  
>  	if (p_data->nb.notifier_call) {
>  		ret = cpufreq_unregister_notifier(&p_data->nb,
> @@ -232,27 +245,9 @@ 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_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);
> -	}
> +	delete_parent_cpu_data(p_data);
>  
> -	return ret;
> +	return 0;
>  }
>  
>  static int cpufreq_passive_register_notifier(struct devfreq *devfreq)


-- 
Best Regards,
Samsung Electronics
Chanwoo Choi