From mboxrd@z Thu Jan 1 00:00:00 1970 From: Max Krasnyansky Subject: Re: [PATCH] tun: Persistent devices can get stuck in xoff state Date: Thu, 10 Jul 2008 17:53:34 -0700 Message-ID: <4876AF0E.507@qualcomm.com> References: <1215584648-13444-1-git-send-email-maxk@qualcomm.com> <200807091759.39171.borntraeger@de.ibm.com> <48752B60.4050106@qualcomm.com> <20080710.170007.68764077.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: borntraeger@de.ibm.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from wolverine01.qualcomm.com ([199.106.114.254]:9061 "EHLO wolverine01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754877AbYGKAxf (ORCPT ); Thu, 10 Jul 2008 20:53:35 -0400 In-Reply-To: <20080710.170007.68764077.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: David Miller wrote: > From: Max Krasnyansky > Date: Wed, 09 Jul 2008 14:19:28 -0700 > >> Christian Borntraeger wrote: >>> Am Mittwoch, 9. Juli 2008 schrieb Max Krasnyansky: >>>> The scenario goes like this. App stops reading from tun/tap. >>>> TX queue gets full and driver does netif_stop_queue(). >>>> App closes fd and TX queue gets flushed as part of the cleanup. >>>> Next time the app opens tun/tap and starts reading from it but >>>> the xoff state is not cleared. We're stuck. >>>> Normally xoff state is cleared when netdev is brought up. But >>>> in the case of persistent devices this happens only during >>>> initial setup. >>> I was able to reproduce the problem. The patch seems to fix it. >>> >>> Tested-by: Christian Borntraeger >> Oh it definitely fixes that problem. It's very easy to reproduce by just >> suspending (ctrl-z) an app that is ready from the tun, waiting a bit for >> the queue to fill up and then killing the app. I have a simple test app >> that simulates this. It's just that in real life that does not happen >> very often. ie Applications either constantly read from tun or they >> close it. >> >> Thanks a lot for testing and confirming. > > I've applied this, thanks. > > But I had to apply it by hand. You made this against an older > tree, because in the current code there is a get_net() call > right before the new lines you added but in your patch context > it isn't there. Hmm, I though I used latest git tree. Oh, turns out it was 2.6.25.4. Sorry. Thanx for fixing it. Max