linux-kernel - Re: debugging oops after disconnecting Nexio USB touchscreen

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Message-Id: <200912021042.04557.oliver@neukum.org>
Date:	Wed, 2 Dec 2009 10:42:04 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Ondrej Zary <linux@...nbow-software.org>
Cc:	Alan Stern <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: debugging oops after disconnecting Nexio USB touchscreen

Am Mittwoch, 2. Dezember 2009 09:52:08 schrieb Ondrej Zary:
> It shows "prev is NULL, qh=f6581080, ehci->async=f6581000".
> 
> The problem is that activating usbmon causes the problem to disappear. No
>  errors in maybe 15 attempts. It appeared on 2nd attempt after unloading
>  usbmon.

That suggests a use after free bug, which usbmon prevents holding
an additional reference.
Are you using SLAB_DEBUG?

	Regards
		Oliver
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