Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to_trip()

Rafael J. Wysocki
2024-08-21T10:52:07Z

On Wed, Aug 21, 2024 at 12:43 PM lihuisong (C) <lihuisong@huawei.com> wrote:
>
>
> 在 2024/8/19 23:51, Rafael J. Wysocki 写道:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > It is not necessary to look up the thermal zone and the cooling device
> > in the respective global lists to check whether or not they are
> > registered. It is sufficient to check whether or not their respective
> > list nodes are empty for this purpose.
> >
> > Use the above observation to simplify thermal_bind_cdev_to_trip(). In
> > addition, eliminate an unnecessary ternary operator from it.
> >
> > Moreover, add lockdep_assert_held() for thermal_list_lock to it because
> > that lock must be held by its callers when it is running.
> >
> > No intentional functional impact.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >
> > v1 -> v3: No changes
> >
> > ---
> > drivers/thermal/thermal_core.c | 16 ++++------------
> > 1 file changed, 4 insertions(+), 12 deletions(-)
> >
> > Index: linux-pm/drivers/thermal/thermal_core.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_core.c
> > +++ linux-pm/drivers/thermal/thermal_core.c
> > @@ -781,25 +781,17 @@ int thermal_bind_cdev_to_trip(struct the
> > {
> > struct thermal_instance *dev;
> > struct thermal_instance *pos;
> > - struct thermal_zone_device *pos1;
> > - struct thermal_cooling_device *pos2;
> > bool upper_no_limit;
> > int result;
> >
> > - list_for_each_entry(pos1, &thermal_tz_list, node) {
> > - if (pos1 == tz)
> > - break;
> > - }
> > - list_for_each_entry(pos2, &thermal_cdev_list, node) {
> > - if (pos2 == cdev)
> > - break;
> > - }
> > + lockdep_assert_held(&thermal_list_lock);
> >
> > - if (tz != pos1 || cdev != pos2)
> > + if (list_empty(&tz->node) || list_empty(&cdev->node))
> The old verification is ensure that tz and cdev already add to
> thermal_tz_list and thermal_cdev_list，respectively.
> Namely, tz and cdev are definitely registered and intialized.
> The check is ok for all untizalized thermal_zone_device and cooling device.
> But the new verification doesn't seem to do that.

It doesn't need to do it and after this series it is only called from
thermal_zone_device_register_with_trips() and
__thermal_cooling_device_register() via thermal_zone_cdev_binding()
after both the cdev and the tz have been added to the list, under
thermal_list_lock.

I guess I can send a patch to remove the check altogether now.