On Tue, Oct 26, 2021 at 11:37:30PM +0800, Ming Lei wrote: > On Tue, Oct 26, 2021 at 10:48:18AM +0200, Petr Mladek wrote: > > Livepatch code never called kobject_del() under a lock. It would cause > > the obvious deadlock. Never? > > The historic code only waited in the > > module_exit() callback until the sysfs interface was removed. > > OK, then Luis shouldn't consider livepatching as one such issue to solve > with one generic solution. It's not what I was told when the deadlock was found with zram, so I was informed quite the contrary. I'm working on a generic coccinelle patch which hunts for actual cases using iteration (a feature of coccinelle for complex searches). The search is pretty involved, so I don't think I'll have an answer to this soon. Since the question of how generic this deadlock is remains questionable, I think it makes sense to put the generic deadlock fix off the table for now, and we address this once we have a more concrete search with coccinelle. But to say we *don't* have drivers which can cause this is obviously wrong as well, from a cursory search so far. But let's wait and see how big this list actually is. I'll drop the deadlock generic fixes and move on with at least a starter kernfs / sysfs tests. Luis
