Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753100AbaGJPul (ORCPT ); Thu, 10 Jul 2014 11:50:41 -0400 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:41041 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751517AbaGJPuk (ORCPT ); Thu, 10 Jul 2014 11:50:40 -0400 Date: Thu, 10 Jul 2014 16:50:03 +0100 From: One Thousand Gnomes To: David Laight Cc: "'Olivier Sobrie'" , David Miller , "j.dumon@option.com" , "linux-usb@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 2/2] hso: fix deadlock when receiving bursts of data Message-ID: <20140710165003.0309924e@alan.etchedpixels.co.uk> In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D17270044@AcuExch.aculab.com> References: <1404723967-24245-1-git-send-email-olivier@sobrie.be> <1404723967-24245-2-git-send-email-olivier@sobrie.be> <20140708.161633.2130069042930765600.davem@davemloft.net> <20140710142848.GA28056@hposo> <063D6719AE5E284EB5DD2968C1650D6D17270044@AcuExch.aculab.com> Organization: Intel Corporation X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 10 Jul 2014 14:37:37 +0000 David Laight 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. Arguably what we need are tty fastpaths for non N_TTY but thats rather more work. There's no fundamental reason that hso can't throw the buffer at buffer straight at the PPP ldisc and straight into the network stack - just that 1. The tty mid layer glue is standing in the way 2. The change of line discipline code has to lock against it Alan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/