linux-kernel - Re: [PATCH] USB: cdc-acm: Prevent data loss when filling tty buffer.

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Message-ID: <4D89E479.7000100@realvnc.com>
Date:	Wed, 23 Mar 2011 12:15:53 +0000
From:	Toby Gray <toby.gray@...lvnc.com>
To:	Oliver Neukum <oneukum@...e.de>
CC:	Greg Kroah-Hartman <gregkh@...e.de>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: cdc-acm: Prevent data loss when filling tty buffer.

On 22/03/2011 07:43, Oliver Neukum wrote:
> Have you tested whether the driver recovers from running out of buffers?
> Other than that it is looking good to me.
I had tested the driver running out of buffers quite extensively, but I 
think I must have just been lucky with the timings. Now that I've had a 
look at the code in more detail, I believe it would be possible for a 
throttle/unthrottle not to occur, in which case no more new URB reads 
would be submitted.

I've attached a v3 version of the patch which ensures that either the 
tty is throttled or the tasklet is rescheduled. I assume that it would 
be preferable to wait until Johan Hovold's '[PATCH 16/16] USB: cdc-acm: 
re-write read processing' has been submitted and then for me to submit 
another similar patch to this one, but which doesn't need the rx tasklet.

I decided it was still worth attaching the patch as it'll allow people 
to fix this issue on older kernel versions

Regards,

Toby

View attachment "0001-USB-cdc-acm-Prevent-data-loss-when-filling-tty-buffe.patch" of type "text/x-patch" (6357 bytes)