Re: [PATCH 1/1] thermal: core: call thermal_zone_device_update() after mode update

Eduardo Valentin
2016-07-01T20:53:46Z

On Thu, Jun 23, 2016 at 02:27:12PM +0200, Rafael J. Wysocki wrote:
> On Wed, Jun 22, 2016 at 7:06 AM, Eduardo Valentin <edubezval@gmail.com> wrote:
> > Because several drivers do the following pattern:
> > .set_mode()
> > ...
> > local_data->mode = new_mode;
> > thermal_zone_device_update(tz);
> >
> > makes sense to simply do the thermal_zone_device_update()
> > in thermal core, after setting the new mode.
> >
> > Also, this patch also remove deadlocks on drivers that
> > call thermal_zone_device_update() on .set_mode(),
> > as .set_mode() is now called always with tz->lock held.
>
> To me, this part of the patch is way more important than the
> optimization mentioned before.
>
> Apparently, the problem is that drivers deadlock, because the
> thermal_zone_device_update() invoked from ->set_mode() is called under
> tz->lock.
>
> So to address that problem you make the core call
> thermal_zone_device_update() after ->set_mode() outside of tz->lock
> and the drivers don't have to do it any more.
>
> Is that correct?

Yes this is correct. The optimization is simply a consequence of the bug
fix, as reported by Keerthy.

>
> Thanks,
> Rafael