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. --- Best Regards, Laurentiu
