On Sun, Feb 05, 2023 at 01:12:12AM +0900, Tetsuo Handa wrote: > On 2023/02/05 0:34, Alan Stern wrote: > >> A few of examples: > >> > >> https://syzkaller.appspot.com/bug?extid=2d6ac90723742279e101 > > > > It's hard to figure out what's wrong from looking at the syzbot report. > > What makes you think it is connected with dev->mutex? > > > > At first glance, it seems that the ath6kl driver is trying to flush a > > workqueue while holding a lock or mutex that is needed by one of the > > jobs in the workqueue. That's obviously never going to work, no matter > > what sort of lockdep validation gets used. > > That lock is exactly dev->mutex where lockdep validation is disabled. > If lockdep validation on dev->mutex were not disabled, we can catch > possibility of deadlock before khungtaskd reports real deadlock as hung. > > Lockdep validation on dev->mutex being disabled is really annoying, and > I want to make lockdep validation on dev->mutex enabled; that is the > "drivers/core: Remove lockdep_set_novalidate_class() usage" patch. > Even if it is always safe to acquire a child device's lock while holding > the parent's lock, disabling lockdep checks completely on device's lock is > not safe. I understand the problem you want to solve, and I understand that it can be frustrating. However, I do not believe you will be able to solve this problem. Alan Stern
