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

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Date:   Tue, 27 Dec 2022 06:32:53 +0000
From:   "Yuan, Perry" <Perry.Yuan@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        "Huang, Ray" <Ray.Huang@....com>,
        "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        "Meng, Li (Jassmine)" <Li.Meng@....com>,
        "Karny, Wyes" <Wyes.Karny@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v9 04/13] cpufreq: amd-pstate: fix kernel hang issue while
 amd-pstate unregistering

[AMD Official Use Only - General]

Hi Viresh.

> -----Original Message-----
> From: Viresh Kumar <viresh.kumar@...aro.org>
> Sent: Tuesday, December 27, 2022 10:54 AM
> To: Yuan, Perry <Perry.Yuan@....com>
> Cc: rafael.j.wysocki@...el.com; Limonciello, Mario
> <Mario.Limonciello@....com>; Huang, Ray <Ray.Huang@....com>;
> Sharma, Deepak <Deepak.Sharma@....com>; Fontenot, Nathan
> <Nathan.Fontenot@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Huang, Shimmer
> <Shimmer.Huang@....com>; Du, Xiaojian <Xiaojian.Du@....com>; Meng,
> Li (Jassmine) <Li.Meng@....com>; Karny, Wyes <Wyes.Karny@....com>;
> linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org
> 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@....com>
> > Reviewed-by: Mario Limonciello <mario.limonciello@....com>
> > Signed-off-by: Perry Yuan <perry.yuan@....com>
> > Cc: stable@...r.kernel.org
> > ---
> >  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.