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

Could please those of you, who are able to reproduce the problem, verify
whether the patch below (completely untested) makes everything behave
again? Thanks.



drivers/hid/usbhid/hiddev.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 254a003..0dcb79a 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -266,13 +266,15 @@ static int hiddev_open(struct inode *inode, struct file *file)
{
struct hiddev_list *list;
struct usb_interface *intf;
+ struct hid_device *hid;
struct hiddev *hiddev;
int res;

intf = usb_find_interface(&hiddev_driver, iminor(inode));
if (!intf)
return -ENODEV;
- hiddev = usb_get_intfdata(intf);
+ hid = usb_get_intfdata(intf);
+ hiddev = hid->hiddev;

if (!(list = kzalloc(sizeof(struct hiddev_list), GFP_KERNEL)))
return -ENOMEM;
@@ -888,7 +890,6 @@ int hiddev_connect(struct hid_device *hid, unsigned int force)
hid->hiddev = hiddev;
hiddev->hid = hid;
hiddev->exist = 1;
- usb_set_intfdata(usbhid->intf, usbhid);
retval = usb_register_dev(usbhid->intf, &hiddev_class);
if (retval) {
err_hid("Not able to get a minor for this device.");

--
Jiri Kosina
SUSE Labs, Novell Inc.


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