On Wed, May 27, 2020 at 9:50 AM Heikki Krogerus <heikki.kroge...@linux.intel.com> wrote: > > On Tue, May 26, 2020 at 10:26:23AM +0200, Rafael J. Wysocki wrote: > > On Tue, May 26, 2020 at 7:58 AM Greg Kroah-Hartman > > <gre...@linuxfoundation.org> wrote: > > > > > > On Mon, May 25, 2020 at 03:49:01PM -0700, Dmitry Torokhov wrote: > > > > On Sun, May 24, 2020 at 8:34 AM Greg Kroah-Hartman > > > > <gre...@linuxfoundation.org> wrote: > > > > > > > > > > It is possible for a KOBJ_REMOVE uevent to be sent to userspace way > > > > > after the files are actually gone from sysfs, due to how reference > > > > > counting for kobjects work. This should not be a problem, but it > > > > > would > > > > > be good to properly send the information when things are going away, > > > > > not > > > > > at some later point in time in the future. > > > > > > > > > > Before this move, if a kobject's parent was torn down before the > > > > > child, > > > > > > > > ^^^^ And this is the root of the problem and what has to be fixed. > > > > > > I fixed that in patch one of this series. Turns out the user of the > > > kobject was not even expecting that to happen. > > > > > > > > when the call to kobject_uevent() happened, the parent walk to try to > > > > > reconstruct the full path of the kobject could be a total mess and > > > > > cause > > > > > crashes. It's not good to try to tear down a kobject tree from top > > > > > down, but let's at least try to not to crash if a user does so. > > > > > > > > One can try, but if we keep proper reference counting then kobject > > > > core should take care of actually releasing objects in the right > > > > order. I do not think you should keep this patch, and instead see if > > > > we can push call to kobject_put(kobj->parent) into kobject_cleanup(). > > > > > > I tried that, but there was a _lot_ of underflow errors reported, so > > > there's something else happening. Or my attempt was incorrect :) > > > > So it looks like there is something in there that's been overlooked so far. > > > > I'll try to look at the Guenter's traces and figure out what went > > wrong after the Heikki's patch. > > At least one problem with that patch was that I was releasing the > parent reference unconditionally.
That actually may be sufficient to explain all of the problems introduced by it.
