From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King Subject: Re: [PATCH] kernel/printk.c: Concerns about the console handover Date: Fri, 21 Sep 2007 14:06:00 +0100 Message-ID: <20070921130600.GB20277@flint.arm.linux.org.uk> References: <20070921010349.2caee558.akpm@linux-foundation.org> <46F3BC3A.8060703@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:36451 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757838AbXIUNKj (ORCPT ); Fri, 21 Sep 2007 09:10:39 -0400 Content-Disposition: inline In-Reply-To: <46F3BC3A.8060703@redhat.com> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Gerd Hoffmann Cc: Andrew Morton , "Maciej W. Rozycki" , Gerd Hoffmann , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Yinghai.Lu@Sun.COM, bryan.wu@analog.com, dilinger@queued.net, lethal@linux-sh.org, rgetz@blackfin.uclinux.org, vapier.adi@gmail.com On Fri, Sep 21, 2007 at 02:42:34PM +0200, Gerd Hoffmann wrote: > Andrew Morton wrote: > > On Thu, 20 Sep 2007 18:28:49 +0100 (BST) "Maciej W. Rozycki" wrote: > > > >> Move the hadover message to after the boot console has been released to > >> avoid bad interactions between it and the real console. > > [ longish problem discussion snipped ] > > >> considered fully disabled. Below is a change which makes the problem > >> disappear for me, but I suppose there was a deliberate reason for placing > >> the printk() where it is now and nowhere else. > > Well, I placed the printk there is for user interface reasons. I think > especially in case the early console and the real console go to > different physical devices it is useful to have the reason it stops > printing messages displayed on the early console. So people don't think > the computer hangs although it just prints messages elsewhere ... > > If that isn't going to work due to two instances not knowing each other > (kernel & firmware) should not mess with the same physical device, then > I'd just drop the printk. And I see no pretty and easy way around that > issue :-( > > We could do the printk and unregister before we setup the new console. > Which has the drawback that we are in trouble in case the setup() call > for the new console fails ... > > We could split the printk into two, one early ("trying to setup new > console foo") which goes to the boot console, then (assuming the setup > worked ok) unregister silently and print a message about the successful > init and boot console unregister on the new console only. Which results > in two lines being printed for the handover when both consoles address > the same physical device. Not that nice IMHO, but maybe still the best > way to handle it. I had an issue with the console initialisation on serial ports, which I discovered during my PXA work. My reason for asking about the kernel versions (which Andrew forwarded to LKML) is to determine whether the report is as a result of those changes, or lack of those changes. Those -mm versions with git-arm in probably have that change. Ergo the importance to answer this question about kernel versions. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: