From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964906AbWFSVli (ORCPT ); Mon, 19 Jun 2006 17:41:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964907AbWFSVli (ORCPT ); Mon, 19 Jun 2006 17:41:38 -0400 Received: from mail-in-09.arcor-online.net ([151.189.21.49]:16780 "EHLO mail-in-09.arcor-online.net") by vger.kernel.org with ESMTP id S964906AbWFSVlg (ORCPT ); Mon, 19 Jun 2006 17:41:36 -0400 From: Bodo Eggert <7eggert@elstempel.de> Subject: Re: [RFC/SERIOUS] grilling troubled CPUs for fun and profit? To: "linux-os (Dick Johnson)" , Andreas Mohr , linux-kernel@vger.kernel.org Reply-To: 7eggert@gmx.de Date: Mon, 19 Jun 2006 23:40:46 +0200 References: <6pxs2-1AR-5@gated-at.bofh.it> <6pyer-2Pt-1@gated-at.bofh.it> User-Agent: KNode/0.7.2 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8Bit X-Troll: Tanz Message-Id: X-be10.7eggert.dyndns.org-MailScanner-Information: See www.mailscanner.info for information X-be10.7eggert.dyndns.org-MailScanner: Found to be clean X-be10.7eggert.dyndns.org-MailScanner-From: 7eggert@elstempel.de Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org linux-os (Dick Johnson) wrote: > On Mon, 19 Jun 2006, Andreas Mohr wrote: >> while looking for loop places to apply cpu_relax() to, I found the >> following gems: >> >> arch/i386/kernel/crash.c/crash_nmi_callback(): >> >> /* Assume hlt works */ >> halt(); >> for(;;); >> >> return 1; >> } This will result in the processor burning energy again after the first interrupt, won't it? >> arch/i386/kernel/doublefault.c/doublefault_fn(): >> >> for (;;) /* nothing */; >> } >> >> Let's assume that we have a less than moderate fan failure that causes >> the CPU to heat up beyond the critical limit... >> That might result in - you guessed it - crashes or doublefaults. >> In which case we enter the corresponding handler and do... what? > > The double-fault is just a place-holder. The CPU will actually > reset without even executing this (try it). If it does reset, you don't need that fuctions (you can use anything), and if not, doing while(1) halt(); in both cases should DTRT even if the system is FUBAR, and it should be even smaller. >> Exactly, we accelerate the CPUs happy march into bit heaven by letting it >> execute a busy-loop under a non-working fan. > > You accelerate nothing. Bit heaven? A CPU without a fan will go into > a cold, cold, shutdown, requiring a hardware reset to get it out of > that latched, no internal clock running, mode. Some CPU may do this, others will go via the random-generator mode into the self-deformation-mode instead. -- Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF verbreiteten Lügen zu sabotieren. http://david.woodhou.se/why-not-spf.html