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

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Date:	Tue, 12 Aug 2014 21:04:30 +0300
From:	Oleksandr Natalenko <oleksandr@...alenko.name>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [BUG] oops in cpufreq driver with AMD Kaveri CPU

Well, I've added the following code to cpufreq_register_notifier() 
(drivers/cpufreq/cpufreq.c) to CPUFREQ_TRANSITION_NOTIFIER case:

===
pr_info("Registered transition notifier: %p, (%p)\n", nb->notifier_call, &nb-
>notifier_call);
===

And got the following in my dmesg (only 1 line):

===
$ cat /var/log/kern.log | grep "Registered transition notifier"
Aug 12 17:23:45 defiant kernel: [    3.084977] cpufreq: Registered transition 
notifier: ffffffff81590378, (ffffffff81cb0ba0)
===

System.map tells me, that ffffffff81590378 corresponds to 
cpufreq_stat_notifier_trans() (in drivers/cpufreq/cpufreq_stats.c).

Also I've added

===
pr_info("%s\n", __func__);
===

to all callbacks (hello, LXR :)), and got the following occurrences in dmesg:

===
$ cat /var/log/kern.log | egrep -e '(acpi_|cpufreq|notifier)' | awk 
'{print($7)}' | sort -u
acpi_processor_ppc_notifier
acpi_thermal_cpufreq_notifier
cpufreq_stat_notifier_policy
===

No extra notifiers are involved so far, but also I haven't caught new hang yet 
as it occurs randomly. Still waiting for it, but I hope my little 
investigation could help somehow.

On Tuesday 12 August 2014 13:16:25 Viresh Kumar wrote:
> On Tue, Aug 12, 2014 at 12:56 PM, Oleksandr Natalenko
> 
> <oleksandr@...alenko.name> wrote:
> > 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?
> Notifiers are used from the cpufreq core when frequency is changed.
> And the powersave governor should have changed the frequency only
> ONCE, i.e. to go to lowest frequency.
> 
> So, it probably happened at the first & only change at that time as well..
> But it shouldn't happen any later. So, see what the log looks like on
> that crash.
-- 
Oleksandr post-factum Natalenko, MSc
pf-kernel community
https://natalenko.name/
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