linux-kernel - Re: [PATCH] p54usb: fix usb_kill_urb hang with slub

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Message-ID: <20081205232321.GA8557@suse.de>
Date:	Fri, 5 Dec 2008 15:23:21 -0800
From:	Greg KH <gregkh@...e.de>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	Christian Lamparter <chunkeey@....de>,
	linux-wireless@...r.kernel.org,
	Johannes Berg <johannes@...solutions.net>,
	John W Linville <linville@...driver.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] p54usb: fix usb_kill_urb hang with slub_debug=P

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
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