Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161276AbXBGM7T (ORCPT ); Wed, 7 Feb 2007 07:59:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965563AbXBGM7T (ORCPT ); Wed, 7 Feb 2007 07:59:19 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:2114 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965542AbXBGM7S (ORCPT ); Wed, 7 Feb 2007 07:59:18 -0500 Date: Wed, 7 Feb 2007 12:35:52 +0000 From: Pavel Machek To: Zachary Amsden Cc: Andi Kleen , Linux Kernel Mailing List , Andrew Morton , Rusty Russell , Jeremy Fitzhardinge , Chris Wright Subject: Re: [PATCH 9/11] Panic delay fix Message-ID: <20070207123552.GD4481@ucw.cz> References: <200702060353.l163rUmj000771@zach-dev.vmware.com> <20070206122729.GC47229@muc.de> <45C8FA2D.6010706@vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45C8FA2D.6010706@vmware.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1403 Lines: 38 Hi! > > > >>Failure to use real-time delay here causes the > >>keyboard to become demonically > >>possessed in the event of a kernel crash, with wildly > >>blinking lights and > >>unpredictable behavior. This has resulted in several > >>injuries. > > > >There must be a reason why it wasn't default before. > >Has this > >reason changed? > > This only matters under paravirt; non-paravirt kernels > and kernels running on native hardware will always > behave properly. > > But paravirtualized kernels with fake devices have no > need to udelay to accommodate slow hardware - the > hardware is just virtual. The USE_REAL_TIME_DELAY > define allows udelay to be specifically reverted back to > being a real delay. There are only a couple cases where Ugh, it sounds like paravirt is more b0rken then I thought. It should always to the proper delay, then replace those udelays that are not needed on virtualized hardware with something else. Just magically defining udelay into nop is broken. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/