RE: [PATCH v9 04/13] cpufreq: amd-pstate: fix kernel hang issue while amd-pstate unregistering

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Viresh.

> -----Original Message-----
> From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Sent: Tuesday, December 27, 2022 10:54 AM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> Cc: rafael.j.wysocki@xxxxxxxxx; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; Huang, Ray <Ray.Huang@xxxxxxx>;
> Sharma, Deepak <Deepak.Sharma@xxxxxxx>; Fontenot, Nathan
> <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng,
> Li (Jassmine) <Li.Meng@xxxxxxx>; Karny, Wyes <Wyes.Karny@xxxxxxx>;
> linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v9 04/13] cpufreq: amd-pstate: fix kernel hang issue
> while amd-pstate unregistering
> 
> On 26-12-22, 00:34, Perry Yuan wrote:
> > In the amd_pstate_adjust_perf(), there is one cpufreq_cpu_get() call
> > to increase increments the kobject reference count of policy and make
> > it as busy. Therefore, a corresponding call to cpufreq_cpu_put() is
> > needed to decrement the kobject reference count back, it will resolve
> > the kernel hang issue when unregistering the amd-pstate driver and
> > register the `amd_pstate_epp` driver instance.
> >
> > Acked-by: Huang Rui <ray.huang@xxxxxxx>
> > Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > Signed-off-by: Perry Yuan <perry.yuan@xxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> >  drivers/cpufreq/amd-pstate.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 204e39006dda..c17bd845f5fc 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -307,6 +307,7 @@ static void amd_pstate_adjust_perf(unsigned int
> cpu,
> >  		max_perf = min_perf;
> >
> >  	amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true);
> > +	cpufreq_cpu_put(policy);
> >  }
> >
> >  static int amd_get_min_freq(struct amd_cpudata *cpudata)
> 
> This should have been sent separately and not in this series. It is a bug fix,
> which could have been merged in the 6.1 itself and now is candidate for 6.2-
> rc1, while the rest of the series needs to wait for 6.3.
> 
> --
> Viresh

Thanks for your feedback, will extract the patch and send it out separately.

Perry.