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

[Viresh Kumar]

On 11 November 2014 17:48, Prarit Bhargava <prarit@xxxxxxxxxx> wrote:
> the problem is tht the userful information is the values of initialized,
> enabled, and what the  event was :(
>
> in every case i ended up needing the values.

So, just add a pr_debug instead and let every thing crash as it does today.

>>> @@ -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 ?
>>
>
> we null pointer panic later on, and again the useful values are the ones displayed.

For the values, I would add a pr_debug() for all cases. And maybe just
do s/WARN_ON/BUG_ON

>>>         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 ? :)
>
> oh, is that right?  i'll look into that.

What is right? sorry couldn't understand :(
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