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From: Oleksandr Natalenko <oleksandr@natalenko.name>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>
Subject: Re: [BUG] oops in cpufreq driver with AMD Kaveri CPU
Date: Tue, 12 Aug 2014 21:18:09 +0300
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Hmm, looks like I've put pr_info to policy notifier instead of transition 
notifier. Will fix it now and post new logs.

On Tuesday 12 August 2014 21:04:30 Oleksandr Natalenko wrote:
> 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@natalenko.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/