From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756422Ab2ADSmA (ORCPT ); Wed, 4 Jan 2012 13:42:00 -0500 Received: from mail-ee0-f46.google.com ([74.125.83.46]:55068 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190Ab2ADSl4 (ORCPT ); Wed, 4 Jan 2012 13:41:56 -0500 Message-ID: <4F049D6B.6040503@suse.cz> Date: Wed, 04 Jan 2012 19:41:47 +0100 From: Jiri Slaby User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20111223 Thunderbird/10.0 MIME-Version: 1.0 To: Jiri Slaby CC: LKML , Alan Cox , Arnd Bergmann , Greg KH Subject: Re: UV serial regression since 2.6.36 References: <4EDE988B.6010501@suse.cz> In-Reply-To: <4EDE988B.6010501@suse.cz> X-Enigmail-Version: 1.3.4 Content-Type: text/plain; charset=ISO-8859-2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/06/2011 11:34 PM, Jiri Slaby wrote: > Hi, > > In short, the issue causes serial port traffic to stop after some time > on UV machines. Only when serial is used as a console. It worked > perfectly with 2.6.32. It's a standard 16550 on 0x3f8 (well, it's > emulated to be at that port). Also in the PNP subsys. > > To reproduce that 'debug' kernel parameter must not be used. > > The root cause seems to be that the serial "chip" there has problems > with interrupts. It generates some but doesn't indicate it's the source > or somebody clears it (NOINT is set). And when it is supposed to > generate one (on THRE), it does not. So there are bytes in the TX buffer > which are never sent. Until the port is kicked e.g. by "echo h > > /proc/sysrq-trigger". > > The unhandled interrupts were always an issue, but somehow hidden. It > became a real problem with patches post 2.6.32. > > I bisected it to these two commits _together_: > > commit 3f582b8c11014e4ce310d9839fb335164195333f > Author: Arnd Bergmann > Date: Tue Jun 29 22:31:40 2010 +0200 > > serial: fix termios settings in open > > AND > > commit 74c2107759dc6efaa1b9127014be58a742a1e7ac > Author: Alan Cox > Date: Tue Jun 1 22:53:00 2010 +0200 > > serial: Use block_til_ready helper > > Those reverted on the top of 2.6.37 makes it work again. Those reverted > on the top of 3.0 plus mine 3 reverted which removed update_set_termios > completely makes it work again. > > I didn't look closely to why those patches are causing that. Like > c_cflag copy in uart_update_termios and "tty->termios->c_cflag & CBAUD" > test in tty_port_block_til_ready don't look good to me... My vacation is over. I suppose you haven't had a chance to take a look into the regression? (Just in case any of you is looking into that right now to not duplicate the effort.) > thanks, -- js suse labs