Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752047AbXARQwv (ORCPT ); Thu, 18 Jan 2007 11:52:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752049AbXARQwv (ORCPT ); Thu, 18 Jan 2007 11:52:51 -0500 Received: from mail.apcon.com ([66.213.199.210]:30601 "EHLO mail.apcon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752047AbXARQwv (ORCPT ); Thu, 18 Jan 2007 11:52:51 -0500 Subject: Re: A question about break and sysrq on a serial console (2.6.19.1) From: Brian Beattie To: Russell King Cc: linux-kernel@vger.kernel.org In-Reply-To: <20070118164747.GD31418@flint.arm.linux.org.uk> References: <1169078214.16802.17.camel@brianb> <20070118091326.GB32068@flint.arm.linux.org.uk> <1169137187.16802.26.camel@brianb> <20070118164747.GD31418@flint.arm.linux.org.uk> Content-Type: text/plain Organization: APCON, Inc. Date: Thu, 18 Jan 2007 08:52:49 -0800 Message-Id: <1169139169.16802.31.camel@brianb> Mime-Version: 1.0 X-Mailer: Evolution 2.6.3 (2.6.3-1.fc5.5) Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 18 Jan 2007 16:53:04.0728 (UTC) FILETIME=[1F3B2D80:01C73B21] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2266 Lines: 50 On Thu, 2007-01-18 at 16:47 +0000, Russell King wrote: > On Thu, Jan 18, 2007 at 08:19:47AM -0800, Brian Beattie wrote: > > On Thu, 2007-01-18 at 09:13 +0000, Russell King wrote: > > > On Wed, Jan 17, 2007 at 03:56:54PM -0800, Brian Beattie wrote: > > > > I'm trying to do a SYSRQ over a serial console. As I understand it a > > > > break will do that, but I'm not seeing the SYSRQ. In looking at > > > > uart_handle_break() in drivers/serial/8250.c it looks like the code will > > > > toggle port->sysrq, rather than just setting it when the port is a > > > > console. I think the correct code would be to move the "port->sysrq = > > > > 0;" to follow the closing brace on the next line, or am I missing > > > > something. > > > > > > Thereby preventing the action of (which may be to cause a SAK > > > event, which would be rather important on a console to ensure that > > > you're really logging in rather than typing your password into another > > > users program which just looks like a login program.) > > > > > > Note that the sequence for sysrq is: > > > > > > (non-break characters or nothing)

> > > > > well the code as is, is not working. Printk's tell me that > > uart_handle_break() is called repeatedly while the break condition is > > active, toggling port->sysrq so that it's a 50/50 chance on whether > > port->sysrq will be set or cleared when the break condition ends. On > > the other hand the 8250 break condition handling code is not working > > anyway, so the problem may be that the 8250 code is not calling > > uart_handle_break() correctly. > > Please learn to use the "reply to all" button when using mailing lists. I don't post much to LKML, I realized after I hit send I needed to reply all. > > Works fine here. Which UART are you actually using? At a guess, it's > probably a bad clone which does not have a correct break implementation. it's the built-in mpc8349 powerpc uart. > -- Brian Beattie Firmware Engineer APCON, Inc. BrianB@apcon.com - 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/