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

[Greg KH <gregkh@suse.de>]

On Fri, Dec 05, 2008 at 05:18:07PM -0600, Larry Finger wrote:
> 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.

See alan's post on linux-usb, it shows the real cause.

thanks,

greg k-h