On Mon, Nov 21, 2022 at 04:24:52PM +0000, Richard Fitzgerald wrote: > Don't hold sdw_dev_lock while calling the peripheral driver > probe() and remove() callbacks. > > Holding sdw_dev_lock around the probe() and remove() calls > causes a theoretical mutex inversion which lockdep will > assert on. The peripheral driver probe will probably register > a soundcard, which will take ALSA and ASoC locks. During > normal operation a runtime resume suspend can be triggered > while these locks are held and will then take sdw_dev_lock. > > It's not necessary to hold sdw_dev_lock when calling the > probe() and remove(), it is only used to prevent the bus core > calling the driver callbacks if there isn't a driver or the > driver is removing. > > If sdw_dev_lock is held while setting and clearing the > 'probed' flag this is sufficient to guarantee the safety of > callback functions. > > The potential race of a bus event happening while probe() is > executing is the same as the existing race of the bus event > handler taking the mutex first and processing the event > before probe() can run. In both cases the event has already > happened before the driver is probed and ready to accept > callbacks. > > Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx> > --- Reviewed-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx> Thanks, Charles
