linux-kernel - Re: [REGRESSION] "USB: use kfifo to buffer usb-generic serial writes" causes gobi

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Message-Id: <201002230026.02941.oliver@neukum.org>
Date:	Tue, 23 Feb 2010 00:26:02 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Anssi Hannula <anssi.hannula@....fi>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Matthew Garrett <mjg59@...f.ucam.org>, dvomlehn@...co.com,
	gregkh@...e.de, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [REGRESSION] "USB: use kfifo to buffer usb-generic serial writes" causes gobi_loader to hang

Am Montag, 22. Februar 2010 19:35:35 schrieb Anssi Hannula:
> On maanantai 22 helmikuu 2010 17:28:36 Alan Stern wrote:

> > The major difference between the logs is in the way the data get
> > divided up into packets.  In both the successful logs, there are
> > sequences of bulk-OUT packets with lengths like:
> > 
> > 	44, 1, 15, 1, 13
> > 
> > where the unsuccessful transfer just has a single packet of length 74.
> > Also, the successful transfers show a lot of bulk-IN traffic where the
> > unsuccessful transfer doesn't have any.  I don't know if that is
> > relevant, however.
> > 
> > No other differences stand out.
> 
> I guess that would suggest that the device doesn't allow the initialization 
> data to be broken into packets arbitrarily (though some differences seem 
> allowed, as the windows driver transmits them differently).

Hi,

let's try testing this hypothesis. Can you change the following line in
usb_serial_probe():
		if (kfifo_alloc(&port->write_fifo, PAGE_SIZE, GFP_KERNEL))
			goto probe_error;

to:

		if (kfifo_alloc(&port->write_fifo, 64, GFP_KERNEL))
			goto probe_error;

This may shed some light on the behavior.

	Regards
		Oliver
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