On Wed, Mar 01, 2023 at 09:14:44PM +0100, Daniel Lezcano wrote: > The function tegra_tsensor_enable_hw_channel() takes the thermal zone > lock to prevent "a potential" race with a call to set_trips() > callback. > > The driver must not play with the thermal framework core code > internals. > > The tegra_tsensor_enable_hw_channel() is called by: > > - the suspend / resume callbacks > - the probe function after the thermal zones are registered > > The thermal zone lock taken in this function is supposed to protect > from a call to the set_trips() callback which writes in the same > register. > > The potential race is when suspend / resume are called at the same > time as set_trips. This one is called only in > thermal_zone_device_update(). > > - At suspend time, the 'in_suspend' is set, thus the > thermal_zone_device_update() bails out immediately and set_trips is > not called during this moment. > > - At resume time, the thermal zone is updated at PM_POST_SUSPEND, > thus the driver has already set the TH2 temperature. > > - At probe time, we register the thermal zone and then we set the > TH2. The only scenario I can see so far is the interrupt fires, the > thermal_zone_update() is called exactly at the moment > tegra_tsensor_enable_hw_channel() a few lines after registering it. > > Enable the channels before setting up the interrupt. We close the > potential race window without using the thermal zone's lock. > > Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> > Suggested-by: Thierry Reding <thierry.reding@xxxxxxxxx> > --- > drivers/thermal/tegra/tegra30-tsensor.c | 25 ++++++++++++++----------- > 1 file changed, 14 insertions(+), 11 deletions(-) Acked-by: Thierry Reding <treding@xxxxxxxxxx>
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