[Bug 55411] sysfs per-cpu cpufreq subdirs/symlinks screwed up after s2ram

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https://bugzilla.kernel.org/show_bug.cgi?id=55411





--- Comment #38 from Viresh Kumar <viresh.kumar@linaro.org>  2013-03-25 11:23:40 ---
On 25 March 2013 16:45, Duncan <1i5t5.duncan@cox.net> wrote:
> FWIW, with this patch, pre-s2ram and post-resume are indeed consistent,
> but it's not back to where it was.
>
> With this patch, each core is a cpufreq law unto itself.  Maybe that's
> what you meant with the note, maybe not (I know the mapping of sysfs
> files to cpufreq-info output was stated up-thread, but I lost track,
> and how affected vs related maps to hardware vs software coordinated
> and what it all actually means other than what I'm seeing isn't ideal,
> is apparently a bit more than I'm able to keep in my head ATM), but it's
> what I get. The relevant bits of cpufreq-info output:
>
> analyzing CPU 0:
>   CPUs which run at the same hardware frequency: 0
>   CPUs which need to have their frequency coordinated by software: 0
> analyzing CPU 1:
>   CPUs which run at the same hardware frequency: 1
>   CPUs which need to have their frequency coordinated by software: 1
> analyzing CPU 2:
>   CPUs which run at the same hardware frequency: 2
>   CPUs which need to have their frequency coordinated by software: 2
> analyzing CPU 3:
>   CPUs which run at the same hardware frequency: 3
>   CPUs which need to have their frequency coordinated by software: 3
> analyzing CPU 4:
>   CPUs which run at the same hardware frequency: 4
>   CPUs which need to have their frequency coordinated by software: 4
> analyzing CPU 5:
>   CPUs which run at the same hardware frequency: 5
>   CPUs which need to have their frequency coordinated by software: 5
>
> But at least it's consistent:  The same results both before and after a
> suspend/resume cycle.
>
> And given that 3.8 wasn't ideal either, maybe that's good enough for
> this cycle, and a real fix will have to wait until the next commit
> window and stable-tree.  That'd give us more leeway to fix it right, as
> well as a full cycle for testing anything else the "correct" fix might
> dredge up.

This is exactly what i expected and i wrote in Note. Because cpufreq core
does a lot of work based on related_cpus now, its better we don't set it
blindly for x86.

Following code was the only user of relatead_cpus in 3.8 code:

        /* Set governor before ->init, so that driver could check it */
#ifdef CONFIG_HOTPLUG_CPU
        for_each_online_cpu(sibling) {
                struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
                if (cp && cp->governor &&
                    (cpumask_test_cpu(cpu, cp->related_cpus))) {
                        policy->governor = cp->governor;
                        found = 1;
                        break;
                }
        }
#endif


There is no other user of relatead_cpus earlier in cpufreq core and that's why
i wonder why it was added earlier.

But a grep of relatead_cpus for 3.8 showed some interesting users in:
tools/power/cpupower/

I will try to check what they are doing with it, but for the kernel it
was almost unused.
And not it is very much used :)

But for 3.9 i believe this patch should be good enough.

Thanks for testing it.

--
viresh

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