On Tue, Sep 07, 2021 at 06:59:18PM +0300, Laurentiu Tudor wrote: > > > On 7/26/2021 10:59 AM, Laurentiu Tudor wrote: > > > > > > On 7/20/2021 1:27 PM, Andy Shevchenko wrote: > >> On Tue, Jul 20, 2021 at 12:22 PM Laurentiu Tudor > >> <laurentiu.tudor@xxxxxxx> wrote: > >>> On 7/19/2021 3:22 PM, Andy Shevchenko wrote: > >>>> On Mon, Jul 19, 2021 at 03:00:17PM +0300, Laurentiu Tudor wrote: > >>>>> On 7/16/2021 8:21 PM, Jon Nettleton wrote: > >>>>>> On Fri, Jul 16, 2021 at 2:17 PM Andy Shevchenko > >>>>>> <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > >>>>>>> > >>>>>>> On Fri, Jul 16, 2021 at 01:16:02PM +0300, laurentiu.tudor@xxxxxxx wrote: > >>>>>>>> From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx> > >>>>>>>> > >>>>>>>> software_node_notify(), on KOBJ_REMOVE drops the refcount twice on managed > >>>>>>>> software nodes, thus leading to underflow errors. Balance the refcount by > >>>>>>>> bumping it in the device_create_managed_software_node() function. > >>>>>>>> > >>>>>>>> The error [1] was encountered after adding a .shutdown() op to our > >>>>>>>> fsl-mc-bus driver. > >>>>>>> > >>>>>>> Looking into the history of adding ->shutdown() to dwc3 driver (it got reverted > >>>>>>> later on), I can tell that probably something is wrong in the ->shutdown() > >>>>>>> method itself. > >>>>>> > >>>>>> Isn't the other alternative to just remove the second kobject_put from > >>>>>> KOBJ_REMOVE ? > >>>>> > >>>>> Or maybe on top of Heikki's suggestion, replace the calls to > >>>>> sysfs_create_link() from KOBJ_ADD with sysfs_create_link_nowarn()? > >>>> > >>>> _noearn will hide the problem. It was there, it was removed from there. > >>>> Perhaps we have to understand the root cause better (some specific flow?). > >>>> > >>>> Any insight from you on the flow when the issue appears? I.o.w. what happened > >>>> on the big picture that we got into the warning you see? > >>> > >>> I encountered the initial issue when trying to shut down a system booted > >>> with ACPI but only after adding a .shutdown() callback to our bus driver > >>> so that the devices are properly taken down. The problem was that > >>> software_node_notify(), on KOBJ_REMOVE was dropping the reference count > >>> twice leading to an underflow error. My initial proposal was to just > >>> bump the refcount in device_create_managed_software_node(). The device > >>> properties that triggered the problem are created here [1]. > >>> > >>> Heikko suggested that instead of manually incrementing the refcount to > >>> use software_node_notify(KOBJ_ADD). This triggered the second issue, a > >>> duplicated sysfs entry warning originating in the usb subsystem: > >>> device_create_managed_software_node() ends up being called twice, once > >>> here [2] and secondly, the place I previous mentioned [1]. > >> > >> This [3] is what I have reported against DWC3 when ->shutdown() has > >> been added there. And here [4] is another thread about the issue with > >> that callback. The ->release() callback is called at put_device() [5] > >> and ->shutdown() is called before that [6]. That said, can you inspect > >> your ->shutdown() implementation once more time and perhaps see if > >> there is anything that can be amended? > >> > > > > Will do, thanks for the pointers. It could be that we mess something out > > in how we use the driver model. > > > > Quick (and late, sorry) update from my side. I've spent time on > debugging our bus, did found some issues but, at least for now, none are > related to sw node. > In the mean time, I noticed in the swnode code that > device_add_software_node() calls software_node_notify(KOBJ_ADD) while > device_create_managed_software_node() doesn't. Updating [1] the later > with the call to software_node_notify(KOBJ_ADD) does seem to fix the > issue I'm seeing. > > Could this be a problem? Any comments appreciated. > > One more thing perhaps worth mentioning is that, at least for now, there > are few uses for this device_create_managed_software_node() api, > mentioning here a couple of them: > - arm64 iort code - this seems to be triggering the issue i'm getting > - dwc3 usb - Andy reported similar issues here, maybe the issue is common? > > [1] > @@ -1113,6 +1125,15 @@ int device_create_managed_software_node(struct > device *dev, > to_swnode(fwnode)->managed = true; > set_secondary_fwnode(dev, fwnode); > > + /* > + * If the device has been fully registered by the time this > function is > + * called, software_node_notify() must be called separately so > that the > + * symlinks get created and the reference count of the node is > kept in > + * balance. > + */ > + if (device_is_registered(dev)) > + software_node_notify(dev, KOBJ_ADD); > + > return 0; > } That should be fixed indeed. Please send that after -rc1 is out. thanks, -- heikki
