On Mon, Jun 1, 2020 at 6:31 PM Johan Hovold <johan@xxxxxxxxxx> wrote: > On Mon, Jun 01, 2020 at 06:09:23PM +0300, Andy Shevchenko wrote: > > On Mon, Jun 1, 2020 at 5:29 PM Johan Hovold <johan@xxxxxxxxxx> wrote: > > > On Mon, Jun 01, 2020 at 05:08:40PM +0300, Andy Shevchenko wrote: > > > > On Mon, Jun 1, 2020 at 5:01 PM Johan Hovold <johan@xxxxxxxxxx> wrote: > > > > > On Mon, Jun 01, 2020 at 04:51:01PM +0300, Andy Shevchenko wrote: ... > > > > > That's not the issue here. The child driver is allocating memory for the > > > > > class device (for example using devres), and that will end up being > > > > > freed on unbind while said device is still registered. The child driver > > > > > may then even be unloaded. No extra reference can fix this. > > > > > > > > Okay, I didn't still get how dropping devres will help here. > > > > Any driver which frees a resource before making sure it's no longer used > > > it is just plain broken. Unfortunately, devres makes this harder to > > > reason about and people get it wrong. This is roughly the current > > > situation with these drivers: > > > > > > drv->probe(dev) > > > foo = devm_kzalloc(dev); > > > > > devm_foo_register(dev->parent, foo); // NOTE: dev->parent > > > > A-ha! Thanks for this detail. > > But why are they doing so? > > As I mentioned in a commit message, we have quite a few MFD drivers that > register class devices under the parent device directly and have been > doing so for a very long time. > > As this is reflected in sysfs and we may have users relying on the > current topology, changing this shouldn't be taken too lightly (drivers > may also depend on it). And in any case, it wouldn't be stable material > to fix the regressions at hand. I see. > > > drv->remove(dev) > > > devres_release_all(dev) > > > kfree(foo); // foo still registered > > > > > but foo remains registered until the parent driver is unbound. > > > > Since the last fixes against kobject elimination, shouldn't be this > > simple fixed by not supplying dev->parent above? > > No, that's a separate issue as it also changes the device tree. Thanks for elaboration. -- With Best Regards, Andy Shevchenko
