Re: [PATCH v2 1/2] thermal: core: Reference count the zone in thermal_zone_get_by_id()

[Rafael J. Wysocki]

On Fri, Oct 4, 2024 at 3:52 PM Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
>
>
>
> On 10/4/24 14:48, Rafael J. Wysocki wrote:
> > On Fri, Oct 4, 2024 at 3:43 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> >>
> >> On Fri, Oct 4, 2024 at 3:37 PM Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> >>>
> >>>
> >>>
> >>> On 10/4/24 14:25, Rafael J. Wysocki wrote:
> >>>> Hi Łukasz,
> >>>>
> >>>> On Fri, Oct 4, 2024 at 10:01 AM Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> >>>>>
> >>>>> Hi Rafael,
> >>>>>
> >>>>> On 10/3/24 13:25, Rafael J. Wysocki wrote:
> >>>>>> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >>>>>>
>
> [snip]
>
> >>>>>>
> >>>>>
> >>>>> I wasn't aware of that helpers in cleanup.h.
> >>>>>
> >>>>> Could you help me to understand when this this
> >>>>> 'if (_T) put_device((&_T->device)' will be called?
> >>>>
> >>>> When the pointer variable initialized via the CLASS() macro goes out
> >>>> of scope (that is, before freeing the memory occupied by the pointer
> >>>> itself).
> >>>
> >>>
> >>> OK, so do we still need the old code in
> >>> thermal_zone_device_unregister(), which calls
> >>> put_device(&tz->device) ?
> >>
> >> Yes, we do.
> >>
> >>> Maybe that code can go away?
> >>
> >> That particular one drops the reference acquired by device_register()
> >> and I don't see an alternative clean way to drop it.
> >
> > The problem there is that local variable tz goes out of scope at the
> > end of the function (at least formally) and put_device(&tz->device)
> > needs to be called before the wait_for_completion(&tz->removal) which
> > definitely needs tz to be still around.
>
> OK, I see now. That makes sense. With that feel free to add:
>
> Reviewed-by: Lukasz Luba <lukasz.luba@xxxxxxx>

Thank you!