Bug creating USB endpoints in 2.6.20.x (kernel bug 8198)

Hi,

I have been hitting this bug regularly in the 2.6.20.x kernels:

http://bugzilla.kernel.org/show_bug.cgi?id=8198

What *seems* to be happening is that something (winecfg?) is causing the USB layer to allocate a
new endpoint directory in /sys, and then quickly deallocate it again. However, sometimes the
endpoint directory is deallocated while udevd is still browsing it, and this causes an oops.

The endpoint directory shown in the oops report does not exist if I'm not thrashing the box with
winecfg. On Tejun Heo's suggestion, I put some debug code at the beginning of sysfs_release() to
print a stack-dump and the kobject's path if the attr->owner field contains 0x6b6b6b6b or
0x5a5a5a5a poison:

XXX debug trap owner=6b6b6b6b, path=/class/usb_endpoint/usbdev1.3_ep84
XXX debug stack-dump
 [<c018462a>] sysfs_release+0x70/0xa5
 [<c0151837>] __fput+0x96/0x13c
 [<c014f358>] filp_close+0x51/0x58
 [<c0150351>] sys_close+0x70/0xa7
 [<c0102bde>] sysenter_past_esp+0x5f/0x85
 [<c0270033>] unix_create1+0xa2/0xee
 =======================

Does anyone have any idea what's happening, please? According to /proc/bus/usb/devices, this
particular endpoint should only exist if we are using the Alt > 0 version of this USB device's
interface:

I:  If#= 1 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=snd-usb-audio
I:  If#= 2 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
I:  If#= 2 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=84(I) Atr=01(Isoc) MxPS=  90 Ivl=1ms
I:  If#= 2 Alt= 2 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=84(I) Atr=01(Isoc) MxPS=  46 Ivl=1ms
I:  If#= 2 Alt= 3 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=84(I) Atr=01(Isoc) MxPS=  25 Ivl=1ms
I:  If#= 2 Alt= 4 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=84(I) Atr=01(Isoc) MxPS=  16 Ivl=1ms

Thanks for any help,
Cheers,
Chris



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