On Sat, Feb 04, 2023 at 10:32:11PM +0900, Tetsuo Handa wrote: > Hello. > > There is a long-standing deadlock problem in driver core code caused by > "struct device"->mutex being marked as "do not apply lockdep checks". The marking of a lock does not cause a deadlock problem, so what do you mean exactly by this? Where is the actual deadlock? > We can make this deadlock visible by applying [1], and we can confirm that > there is a deadlock problem that I think needs to be addressed in core code [2]. Any reason why you didn't cc: us on these patches? > Also, since driver developers are taking it for granted that driver callback > functions can behave as if dev->mutex is not held (because possibility of deadlock > was never reported), it would solve many deadlocks in driver code if you can update > driver core code to avoid calling driver callback functions with dev->mutex held > (by e.g. replacing dev->mutex with dev->spinlock and dev->atomic_flags). > But I'm not familiar enough to propose such change... A driver developer should never be messing with the mutex of a device, that's not for them to touch, that's the driver core's lock to touch, right? So I don't understand the real problem here. What subsystem is having issues and what issues are they exactly? And using a spinlock shouldn't change any locking deadlocks that I can tell, so I don't understand the proposal, sorry. thanks, greg k-h
