linux-kernel - Re: [PATCH 2/2] hso: fix deadlock when receiving bursts of data

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Message-ID: <20140711091803.GA19663@hposo>
Date:	Fri, 11 Jul 2014 11:18:03 +0200
From:	Olivier Sobrie <olivier@...rie.be>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	David Laight <David.Laight@...LAB.COM>,
	David Miller <davem@...emloft.net>,
	"j.dumon@...ion.com" <j.dumon@...ion.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] hso: fix deadlock when receiving bursts of data

Hi Alan and Davids,

On Thu, Jul 10, 2014 at 04:50:03PM +0100, One Thousand Gnomes wrote:
> On Thu, 10 Jul 2014 14:37:37 +0000
> David Laight <David.Laight@...LAB.COM> wrote:
> 
> > From: Olivier Sobrie
> > ...
> > > The function put_rxbuf_data() is called from the urb completion handler.
> > > It puts the data of the urb transfer in the tty buffer with
> > > tty_insert_flip_string_flags() and schedules a work queue in order to
> > > push the data to the ldisc.
> > > Problem is that we are in a urb completion handler so we can't wait
> > > until there is room in the tty buffer.
> 
> The tty provides the input queue, if the queue is full then just chuck
> the data in the bitbucket.  hso is trying to be far too clever.
> 
> If hso is fast enough that the buffering isn't sufficient on the tty side
> then we need to fix the tty buffer size.

Ok I'll adapt the patch to drop the data that can't be put in the tty
buffer. I test this and resend a new patch.

Thanks for your help!

-- 
Olivier
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