RE: [PATCH v2] cpufreq: amd-pstate: fix kernel hang issue while amd-pstate unregistering

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Rafael:

> -----Original Message-----
> From: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Sent: Tuesday, January 10, 2023 8:58 PM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> Cc: rafael.j.wysocki@xxxxxxxxx; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; Huang, Ray <Ray.Huang@xxxxxxx>;
> viresh.kumar@xxxxxxxxxx; 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 v2] cpufreq: amd-pstate: fix kernel hang issue while
> amd-pstate unregistering
> 
> On Tue, Jan 10, 2023 at 1:50 PM Perry Yuan <perry.yuan@xxxxxxx> 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>
> > Tested-by: Wyes Karny <wyes.karny@xxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> 
> Can you provide a Fixes tag, please?


Sure, let me add the Fixes tag in v3

> 
> Also, what's the difference between this and the previous version?

Just add the  "Tested-by: Wyes Karny <wyes.karny@xxxxxxx>"  in v2. 

> 
> > ---
> >  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)
> > --
> > 2.34.1
> >