linux-kernel - Re: [PATCH 1/3 v6] cpufreq: Add debugfs directory for cpufreq

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Date:	Wed, 24 Jul 2013 10:35:54 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	rjw@...k.pl, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, cpufreq@...r.kernel.org,
	kyungmin.park@...sung.com, myungjoo.ham@...sung.com,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH 1/3 v6] cpufreq: Add debugfs directory for cpufreq

On 24 July 2013 06:55, Chanwoo Choi <cw00.choi@...sung.com> wrote:
> On 07/22/2013 07:11 PM, Viresh Kumar wrote:
>> On 18 July 2013 16:47, Chanwoo Choi <cw00.choi@...sung.com> wrote:

>>> +static void cpufreq_remove_debugfs_dir(struct cpufreq_policy *policy,
>>> +                                      unsigned int cpu)
>>> +{
>>> +       unsigned int idx = cpumask_weight(policy->cpus) > 1 ? cpu : 0;
>>> +
>>> +       if (!policy->cpu_debugfs[idx])
>>> +               return;
>>> +
>>> +       debugfs_remove_recursive(policy->cpu_debugfs[idx]);
>>
>> Whey do we need recursive here? And what exactly does recursive will
>> do?
>>
>
> If cpu is last user of policy, __cpufreq_remove_dev() have to remove debugfs directory
> and child file/directory of root debugfs directory. So, I used debugfs_remove_recursive() function.

You are calling this routine even when we aren't at the last cpu of a policy.
And so, eventually you are calling this routine for a link you have created.

Have you actually tested your code? What kind of platform? What is cpu
topology ?? And what exactly you tested..

We are already on v6 and this patch still looks like the v1.. It still has lots
of basic mistakes, which I don't expect so later in the series..

Its very difficult for me to review the same patchset again and again.. So,
normally people might not review it well after v3-v4 and just trust the sender..
But I am nowhere close to getting that.. And so discouraged to review it..

Please review/test it well on multiple kind of systems if possible. Test on
your intel laptop and see if it has multiple policy structures with
multiple cpus
in it.. cpuX/cpufreq/related_cpus gives you all cpus that share policy
structure.

>>> +}
>>> +
>>
>> same problem here too.
>>> +static void cpufreq_move_debugfs_dir(struct cpufreq_policy *policy,
>>> +                                    unsigned int new_cpu)
>>> +{
>>> +       struct dentry *old_entry, *new_entry;
>>> +       char new_dir_name[CPUFREQ_NAME_LEN];
>>> +       unsigned int j, old_cpu = policy->cpu;
>>> +
>>> +       if (!policy->cpu_debugfs[new_cpu])
>>> +               return;
>>> +
>>> +       /*
>>> +        * Remove symbolic link of debugfs directory except for debugfs
>>> +        * directory of old_cpu.
>>> +        */
>>> +       for_each_present_cpu(j) {
>>> +               if (old_cpu == j)
>>> +                       continue;
>>> +
>>> +               debugfs_remove(policy->cpu_debugfs[j]);
>>
>> Why you need this? We aren't removing the earlier dentry at all here.

haven't answered this.

>>> +       if (!new_entry) {
>>> +               pr_err("changing debugfs directory name failed\n");
>>> +               goto err_rename;
>>> +       }
>>> +
>>> +       policy->cpu_debugfs[new_cpu] = new_entry;
>>> +       policy->cpu_debugfs[old_cpu] = NULL;
>>> +
>>> +       /* Create again symbolic link of debugfs directory */
>>> +       for_each_present_cpu(j) {
>>
>> present_cpu?? We discussed this before.. You will break multi cluster
>> systems.
>
> My mistake. I'll use for_each_cpu() macro instead of for_each_present_cpu().

Go through earlier comments about this.. you are still wrong.. You need to
run over cpus that are in this policy.. i.e. policy->cpus.

>>> +               if (new_cpu == j)
>>> +                       continue;
>>> +

>>> @@ -1894,6 +2065,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>>>         cpufreq_driver = driver_data;
>>>         write_unlock_irqrestore(&cpufreq_driver_lock, flags);
>>>
>>> +       cpufreq_create_debugfs();
>>
>> Why you moved this to register_driver? It was fine at cpufreq_core_init()
>
> If we moved this to cpufreq_core_int(), I have to create cpufreq_core_exit().
> Do you agree about creating cpufreq_core_exit()(?

No you don't need that routine. Or in other words there isn't any exit
for cpufreq core and so this directory must not be removed.
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