Re: [PATCH v1 4/4] ACPI: processor: thermal: Update CPU cooling devices on cpufreq policy changes

Zhang, Rui
2023-03-12T14:44:26Z

On Fri, 2023-03-10 at 19:29 +0100, Rafael J. Wysocki wrote:
> On Tue, Mar 7, 2023 at 5:47 PM Zhang, Rui <rui.zhang@intel.com>
> wrote:
> > On Fri, 2023-03-03 at 20:23 +0100, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > >
> > > When a cpufreq policy appears or goes away, the CPU cooling
> > > devices
> > > for
> > > the CPUs covered by that policy need to be updated so that the
> > > new
> > > processor_get_max_state() value is stored as max_state and the
> > > statistics in sysfs are rearranged for each of them.
> > >
> > > Do that accordingly in acpi_thermal_cpufreq_init() and
> > > acpi_thermal_cpufreq_exit().
> > >
> > > Fixes: a365105c685c("thermal: sysfs: Reuse cdev->max_state")
> > > Reported-by: Wang, Quanxian <quanxian.wang@intel.com>
> > > Link:
> > > https://lore.kernel.org/linux-pm/53ec1f06f61c984100868926f282647e57ecfb2d.camel@intel.com/
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > > ---
> > > drivers/acpi/processor_thermal.c | 16 +++++++++++++---
> > > 1 file changed, 13 insertions(+), 3 deletions(-)
> > >
> > > Index: linux-pm/drivers/acpi/processor_thermal.c
> > > =================================================================
> > > ==
> > > --- linux-pm.orig/drivers/acpi/processor_thermal.c
> > > +++ linux-pm/drivers/acpi/processor_thermal.c
> > > @@ -140,9 +140,14 @@ void acpi_thermal_cpufreq_init(struct cp
> > > ret = freq_qos_add_request(&policy->constraints,
> > > &pr->thermal_req,
> > > FREQ_QOS_MAX, INT_MAX);
> > > - if (ret < 0)
> > > + if (ret < 0) {
> > > pr_err("Failed to add freq constraint for
> > > CPU%d
> > > (%d)\n",
> > > cpu, ret);
> > > + continue;
> > > + }
> > > +
> > > + if (!IS_ERR(pr->cdev))
> > > + thermal_cooling_device_update(pr->cdev);
> >
> > Although thermal_cooling_device_update() handles "pr->cdev == NULL"
> > case, I think it is better to use !IS_ERR_OR_NULL() here.
>
> Why is it?
>
> I was thinking about doing that, but then I realized that the NULL
> case had been covered and that's why I went for the change above. If
> there is a particular reason to check for NULL here, I can do that,
> but I'm not sure what it is.

I don't have a strong objection here.

I thought this was a code bug at first glance, until I double checked t
hermal_cooling_device_update().

So I think the latter would be more straight forward without
introducing code complexity.

thanks,
rui