Re: [PATCH 5/5] cpufreq, add BUG() messages in critical paths to aid debugging failures

[Viresh Kumar]

On 5 November 2014 20:23, Prarit Bhargava <prarit@xxxxxxxxxx> wrote:
> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index b1ee597..f158882 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -161,9 +161,18 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
>  EXPORT_SYMBOL_GPL(dbs_check_cpu);
>
>  static inline void __gov_queue_work(int cpu, struct dbs_data *dbs_data,
> -               unsigned int delay)
> +                                   unsigned int delay,
> +                                   struct cpufreq_policy *policy)
>  {
> -       struct cpu_dbs_common_info *cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);

I will let it crash right here instead of additional code :)

> @@ -258,7 +268,13 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
> -       WARN_ON(!dbs_data && (event != CPUFREQ_GOV_POLICY_INIT));
> +       if (!dbs_data && (event != CPUFREQ_GOV_POLICY_INIT)) {
> +               pr_emerg("governor_data is NULL but governor %s is initialized = %d [governor_enabled = %d event = %u]\n",
> +                        policy->governor->name,
> +                        atomic_read(&policy->governor->initialized),
> +                        policy->governor_enabled, event);
> +               BUG();

How is the BUG better than the WARN here ?

>         switch (event) {
>         case CPUFREQ_GOV_POLICY_INIT:
> @@ -329,6 +345,12 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
>         case CPUFREQ_GOV_POLICY_EXIT:
>                 mutex_lock(&dbs_data->usage_count_mutex);
>                 if (atomic_dec_and_test(&dbs_data->usage_count)) {
> +                       if (atomic_read(&policy->governor->initialized) > 1) {

Isn't this wrong? Consider 4 CPUs with separate clock line and have set
governor-per-policy to true. EXIT will be called for every CPU hotplug and
initialized will be 4 initially..

Or I am still vacation lag'd ? :)

> +                               pr_emerg("Removing governor %s but initialized = %d, dbs_data->usage_count = 0\n",
> +                                        policy->governor->name,
> +                                  atomic_read(&policy->governor->initialized));
> +                               BUG();
> +                       }
>                         sysfs_remove_group(get_governor_parent_kobj(policy),
>                                         get_sysfs_attr(dbs_data));
>
> --
> 1.7.9.3
>
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