On Sat, Feb 04, 2023 at 11:21:27PM +0900, Tetsuo Handa wrote: > On 2023/02/04 22:47, Greg Kroah-Hartman wrote: > > 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? > > A few of examples: > > https://syzkaller.appspot.com/bug?extid=2d6ac90723742279e101 > https://syzkaller.appspot.com/bug?extid=2e39bc6569d281acbcfb > https://syzkaller.appspot.com/bug?extid=9ef743bba3a17c756174 Random links to syzkaller reports that are huge and not descriptive does not actually persuade me as I don't have the inclination to dig through them, sorry. Specific examples, with code, please. > >> 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? > > We can't apply this "drivers/core: Remove lockdep_set_novalidate_class() usage" patch What patch is that? I do not see that in my inbox anywhere. I don't even see it in my lkml archive, so I do not know what you are talking about. > until we fix all lockdep warnings that happen during the boot stage; What lockdep warnings? > otherwise syzbot testing can't work which is more painful than > applying this patch now. Again, I'm totally confused. What is the real bug/problem/issue here? Where is the deadlock? > Therefore, I locally tested this patch (in order not to be applied now). What patch? I'm totally confused. > And I got a lockdep warning on the perf_event code. What warning? > I got next lockdep warning on the driver core code when I tried a fix > for the perf_event code suggested by Peter Zijlstra. Again, what warning? > Since Peter confirmed that this is a problem that led to commit > 1704f47b50b5 ("lockdep: Add novalidate class for dev->mutex > conversion"), this time I'm reporting this problem to you (so that you > can propose a fix for the driver core code). Again, I have no idea what the real problem is! Please show me in the driver core code, where the deadlock is that needs to be resolved. Without that, I can't answer anything... totally and throughly confused, greg k-h
