Re: [PATCH] p54usb: fix usb_kill_urb hang with slub_debug=P

Larry Finger
2008-12-05T23:18:26Z

Greg KH wrote:
> On Fri, Dec 05, 2008 at 03:47:45PM +0100, Christian Lamparter wrote:
>> This patch fixes a problem identified by Johannes Berg.
>
> No, it only papers over the real problem here, let's work on a correct
> patch please.

I can contribute a little info. If SLUB debugging is enabled, and the boot
command includes 'slub_debug=P', I get a GPF in kref_get(), which is called from
kobject_get() with the following code:

if (kobj)
kref_get(&kobj->kref);

>From the dump, &kobj->kref is 0x6b6b6b6b6b6b6dbb, a poisoned value.

Somewhere, the "struct urb" has been freed, but kobj has not been set to NULL.

As everything I've found is a symptom, I'm still looking for the real cause.

Larry