linux-kernel - Re: 2.6.31-rc5 regression: Oops when USB Serial disconnected while in use

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Date:	Fri, 21 Aug 2009 11:25:54 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: 2.6.31-rc5 regression: Oops when USB Serial disconnected while
 in use

On Thu, 20 Aug 2009 17:20:35 Alan Stern <stern@...land.harvard.edu> wrote:
> On Thu, 20 Aug 2009, Bruno [UTF-8] Prémont wrote:
> 
> > No, that one does not really help (well it avoids dereferencing a
> > bad pointer (NULL for pl2302 or invalid for ftdi) with
> > serial_do_free() after destroy_serial() but is does underflow
> > module refcount (refcount ends up at 2^32-1) and lets the kernel
> > stall/panic a short time later without any useful information at
> > that moment (only very first line of trace ever appears) [ftdi for
> > the panic/freeze].
> 
> More information, please.  Does the problem occur with the pl2303 or 
> only with the ftdi?  Which module's refcount underflows?  What else
> can you provide?

The module refcount was for both. It's the pl2302/ftdi-sio module's
refcount.

I don't remember for sure about the panic if it also affects
pl2302 or not.
At least one of the panics was when running dmesg after exiting minicom.

I will redo the tests this evening when I get home and report back with
more details.

> I don't see the same sort of thing with my pl2303 device, but maybe
> I'm using a different version of minicom.
> 
> Alan Stern

Bruno
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