linux-kernel - Re: [PATCH v1 01/10] cpufreq: Reference count policy in cpufreq_update

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Message-ID: <CAJZ5v0h_UzXkT5eS9FPq-UBqTsprhHuGK_YHDVRyPNPcYcKC4A@mail.gmail.com>
Date: Sat, 29 Mar 2025 12:48:50 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, 
	Mario Limonciello <mario.limonciello@....com>, Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v1 01/10] cpufreq: Reference count policy in cpufreq_update_limits()

On Sat, Mar 29, 2025 at 3:02 AM Marek Marczykowski-Górecki
<marmarek@...isiblethingslab.com> wrote:
>
> On Fri, Mar 28, 2025 at 09:39:08PM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Since acpi_processor_notify() can be called before registering a cpufreq
> > driver or even in cases when a cpufreq driver is not registered at all,
> > cpufreq_update_limits() needs to check if a cpufreq driver is present
> > and prevent it from being unregistered.
> >
> > For this purpose, make it call cpufreq_cpu_get() to obtain a cpufreq
> > policy pointer for the given CPU and reference count the corresponding
> > policy object, if present.
> >
> > Fixes: 5a25e3f7cc53 ("cpufreq: intel_pstate: Driver-specific handling of _PPC updates")
> > Closes: https://lore.kernel.org/linux-acpi/Z-ShAR59cTow0KcR@mail-itl
> > Reporetd-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
>
> Reported

Right, thanks!

> I wanted to propose also Tested-by tag, but technically it's not me who
> tested it: https://forum.qubes-os.org/t/kernel-latest-6-13-6-boot-loop/32926/18

You can ask the original tester whether or not they would be willing
to give a tag, though.

> > Cc: All applicable <stable@...r.kernel.org>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/cpufreq/cpufreq.c |    6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -2781,6 +2781,12 @@
> >   */
> >  void cpufreq_update_limits(unsigned int cpu)
> >  {
> > +     struct cpufreq_policy *policy __free(put_cpufreq_policy);
> > +
> > +     policy = cpufreq_cpu_get(cpu);
> > +     if (!policy)
> > +             return;
> > +
> >       if (cpufreq_driver->update_limits)
> >               cpufreq_driver->update_limits(cpu);
> >       else
> >
> >
> >
>
> --
> Best Regards,
> Marek Marczykowski-Górecki
> Invisible Things Lab