Re: [BUG] oops in cpufreq driver with AMD Kaveri CPU

From: Oleksandr Natalenko
Date: Tue Aug 12 2014 - 03:26:45 EST

Got that and will try to investigate ASAP.

Just to note: I tried to use powersave governor and got the same result. I believe notifiers are used with powersave governor as well. Am I wrong?

On August 12, 2014 9:16:21 AM EEST, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>On Tue, Aug 12, 2014 at 11:25 AM, Oleksandr Natalenko
><oleksandr@xxxxxxxxxxxxxx> wrote:
>> What should I do to debug it? Is that necessary to recompile kernel
>with full
>> debug?
>Yeah, you need to recompile the kernel for sure but not necessarily
>with debug
>Some background:
>In cpufreq framework, we manage a CPUs frequency based on the load
>on CPU. You are using ondemand governor which tries to
>increase/decrease frequency
>continuously at fixed intervals.
>Now, when we change the frequency we *may* need to communicate this to
>drivers which *may* depend on CPUs frequency for their functioning.
>This is handled via notifications.
>Other drivers are required to do this:
>to register themselves for frequency-change and them a routine of
>theirs would
>be called from cpufreq-core..
>This is exactly where it is crashing for you. i.e. while calling the
>notifier list.
>So, you need to check which all notifiers are registered and out of
>those which
>one is crashing..
>The first parameter of the above register-call should be declared this
>static struct notifier_block xyz_notifier_block = {
> .notifier_call = xyz_freq_notifier,
>I would have done it this way:
>- Add a print in cpufreq_register_notifier() to print the address of
>present in .notifier_call for case: CPUFREQ_TRANSITION_NOTIFIER
>- Then add prints to all the notifiers added for your configuration,
>be much only 4-5 I believe. i.e. you can add print messages to the
>- Then see the sequence/order in which they are called normally, when
>don't crash.. and check that when it crashes..
>- You will be able to make out which notifier is crashing. And then we
>see why?
>- You can add something like this to notifier routines:
>pr_info("%s\n", __func__);
>This will print function name.
>>> Which patch are you talking about here?
>> I thought about this one [1], but I guess that's not my case.
>> [1]
>I guessed so and I don't think it will help as the crashes reported in
>bug-log is something different.

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Sent from my Android device with K-9 Mail. Please excuse my brevity.
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