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SubjectRe: [BUG] object: is not initialized, yet kobject_put() is being called
On Thu, 12 Aug 2010, Markus Trippelsdorf wrote:

> > > > > > Guys, could you please send me your .config with which you are
> > > > > > experiencing the problem, so that I can try to reproduce it with it?
> > > > >
> > > > > Attached.
> > > >
> > > > So I had to add support for HW of mine (SATA_VIA, PATA_VIA, disabled the
> > > > radeon firmware stuff, and, most importantly, enabled UHCI, which is what
> > > > is on machine I am using now for testing), and disconnect-connect cycle
> > > > works nicely:
> > > >
> > > > usb 3-2: USB disconnect, address 3
> > > > usb 3-2: new low speed USB device using uhci_hcd and address 4
> > > > input: mouse USB mouse with wheel as /devices/pci0000:00/0000:00:10.1/usb3/3-2/3-2:1.0/input/input6
> > > > generic-usb 0003:05B8:3091.0004: input,hidraw0: USB HID v1.10 Mouse [mouse USB mouse with wheel] on usb-0000:00:10.1-2/input0
> > > > input: mouse USB mouse with wheel as /devices/pci0000:00/0000:00:10.1/usb3/3-2/3-2:1.1/input/input7
> > > > generic-usb 0003:05B8:3091.0005: input,hidraw1: USB HID v1.10 Keyboard [mouse USB mouse with wheel] on usb-0000:00:10.1-2/input1
> > > >
> > > > so still no BUG from kobject refcounting, and the hidraw numbers are the
> > > > same. The major difference seems to be that I am using UHCI and you have
> > > > your HID devices connected through OHCI, is that correct?
> > >
> > > Correct. And I should add that it very easy to reproduce here; just
> > > disconnecting the usb receiver triggers the WARNING.
> >
> > Disabling USB_HIDDEV in my .config solves the problem (there is no
> > WARNING anymore when disconnecting the receiver).
>
> Reverting bd25f4dd6972755579d0ea50d1a5ace2e9b00d1a with USB_HIDDEV
> enabled also solves the problem. So there must be a bug in that patch:
>
> commit bd25f4dd6972755579d0ea50d1a5ace2e9b00d1a
> Author: Arnd Bergmann <arnd@arndb.de>
> Date: Sun Jul 11 15:34:05 2010 +0200
>
> HID: hiddev: use usb_find_interface, get rid of BKL
>
> This removes the private hiddev_table in the usbhid
> driver and changes it to use usb_find_interface
> instead.
>
> The advantage is that we can avoid the race between
> usb_register_dev and usb_open and no longer need the
> big kernel lock.
>
> This doesn't introduce race condition -- the intf pointer could be
> invalidated only in hiddev_disconnect() through usb_deregister_dev(),
> but that will block on minor_rwsem and not actually remove the device
> until usb_open().
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Cc: Jiri Kosina <jkosina@suse.cz>
> Cc: "Greg Kroah-Hartman" <gregkh@suse.de>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Thanks, I had my suspicion about this commit (that's why I asked to you
verify with CONFIG_USB_HIDDEV turned off as well).

Adding Arnd to CC and will look into it myself as well soon.

Arnd, the complete thread can be found at
http://lkml.org/lkml/2010/8/10/280

--
Jiri Kosina
SUSE Labs, Novell Inc.


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