linux-kernel - Re: [PATCH v1 1/4] ACPI: processor: Reorder acpi_processor_driver

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Message-ID: <CAJZ5v0hm3S_3eOsVm5vTUX23ynPXhY469ctZUpLdHZFt+b2KHA@mail.gmail.com>
Date:   Mon, 13 Mar 2023 14:48:23 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Zhang, Rui" <rui.zhang@...el.com>
Cc:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "srinivas.pandruvada@...ux.intel.com" 
        <srinivas.pandruvada@...ux.intel.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Wang, Quanxian" <quanxian.wang@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v1 1/4] ACPI: processor: Reorder acpi_processor_driver_init()

On Sun, Mar 12, 2023 at 5:09 PM Zhang, Rui <rui.zhang@...el.com> wrote:
>
> On Fri, 2023-03-03 at 20:19 +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > The cpufreq policy notifier in the ACPI processor driver may as
> > well be registered before the driver itself, which causes
> > acpi_processor_cpufreq_init to be true (unless the notifier
> > registration fails, which is unlikely at that point) when the
> > ACPI CPU thermal cooling devices are registered, so the
> > processor_get_max_state() result does not change while
> > acpi_processor_driver_init() is running.
> >
> > Change the ordering in acpi_processor_driver_init() accordingly
> > to prevent the max_state value from remaining 0 permanently for all
> > ACPI CPU cooling devices.
> >
> > Fixes: a365105c685c("thermal: sysfs: Reuse cdev->max_state")
> > Reported-by: Wang, Quanxian <quanxian.wang@...el.com>
> > Link:
> > https://lore.kernel.org/linux-pm/53ec1f06f61c984100868926f282647e57ecfb2d.camel@intel.com/
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> The full patch series fixes the problem but this one does not.

That is a correct observation, but the $subject patch fixes part of
the problem (which is not addressed by the rest of the series AFAICS)
and so it deserves a Fixes tag of its own IMO.

I guess I should clarify that in the changelog.

> This is because,
>
> static int cpu_has_cpufreq(unsigned int cpu)
> {
>         struct
> cpufreq_policy *policy;
>
>         if (!acpi_processor_cpufreq_init)
>                 return 0;
>
>         policy = cpufreq_cpu_get(cpu);
>         if (policy) {
>                 cpufreq_cpu_put(policy);
>                 return 1;
>         }
>         return 0;
> }
>
> Although acpi_processor_cpufreq_init is set to true with patch 1/4, but
> we don't have cpufreq driver registered, thus cpufreq_cpu_get() return
> NULL.
> so acpi_processor_cpufreq_init is not the only dependency here. :(

Right.  That's why the other patches in the series are needed too.

> > ---
> >  drivers/acpi/processor_driver.c |   12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > Index: linux-pm/drivers/acpi/processor_driver.c
> > ===================================================================
> > --- linux-pm.orig/drivers/acpi/processor_driver.c
> > +++ linux-pm/drivers/acpi/processor_driver.c
> > @@ -263,6 +263,12 @@ static int __init acpi_processor_driver_
> >       if (acpi_disabled)
> >               return 0;
> >
> > +     if (!cpufreq_register_notifier(&acpi_processor_notifier_block,
> > +                                    CPUFREQ_POLICY_NOTIFIER)) {
> > +             acpi_processor_cpufreq_init = true;
> > +             acpi_processor_ignore_ppc_init();
> > +     }
> > +
> >       result = driver_register(&acpi_processor_driver);
> >       if (result < 0)
> >               return result;
> > @@ -276,12 +282,6 @@ static int __init acpi_processor_driver_
> >       cpuhp_setup_state_nocalls(CPUHP_ACPI_CPUDRV_DEAD, "acpi/cpu-
> > drv:dead",
> >                                 NULL, acpi_soft_cpu_dead);
> >
> > -     if (!cpufreq_register_notifier(&acpi_processor_notifier_block,
> > -                                    CPUFREQ_POLICY_NOTIFIER)) {
> > -             acpi_processor_cpufreq_init = true;
> > -             acpi_processor_ignore_ppc_init();
> > -     }
> > -
> >       acpi_processor_throttling_init();
> >       return 0;
> >  err:
> >
> >
> >