From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757641AbYDGWb2 (ORCPT ); Mon, 7 Apr 2008 18:31:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753063AbYDGWbU (ORCPT ); Mon, 7 Apr 2008 18:31:20 -0400 Received: from one.firstfloor.org ([213.235.205.2]:43462 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751997AbYDGWbU (ORCPT ); Mon, 7 Apr 2008 18:31:20 -0400 Date: Tue, 8 Apr 2008 00:35:40 +0200 From: Andi Kleen To: "Rafael J. Wysocki" Cc: Andi Kleen , Jiri Kosina , Zdenek Kabelac , Kernel development list , Ingo Molnar , Thomas Gleixner Subject: Re: BUG: using smp_processor_id() during suspend with 2.6.25-rc8 Message-ID: <20080407223540.GI16647@one.firstfloor.org> References: <20080407222352.GG16647@one.firstfloor.org> <200804080029.31102.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200804080029.31102.rjw@sisk.pl> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 08, 2008 at 12:29:30AM +0200, Rafael J. Wysocki wrote: > On Tuesday, 8 of April 2008, Andi Kleen wrote: > > On Tue, Apr 08, 2008 at 12:11:17AM +0200, Jiri Kosina wrote: > > > On Tue, 8 Apr 2008, Andi Kleen wrote: > > > > > > > > I know. However preempt_count is a little bit inconsistent in such cases > > > > > though. > > > > And? interrupts off beats preempt count anyways. Why did you write the > > > > patch? Was there a (incorrect) warning triggered? > > > > > > Reported at http://lkml.org/lkml/2008/4/7/130 > > > > > > BTW is also mce_init() (called from mce_resume()) guaranteed to run with > > > IRQs off? > > > > [cc rafael] > > > > The mce resume is a sysdev. > > > > sysdevs were always supposed to run completely with interrupts off. If they > > don't anymore that's some kind of higher level resume code bug which you need > > to fix there, not hack around in the low level code. > > They are executed with interrupts disabled, on one CPU. Well then someone enables them incorrectly, see the report above. > > > If it does that it likely broke more code too. > > > > Obviously turning on preemption anywhere around the machine check is > > fatal because it touches CPU state and if you reschedule you could > > switch to another CPU and change or access the wrong CPU's state. > > FWIW, at the point when sysdevs are resumed we are single-threaded. You mean single CPUed? Even a single thread could switch to another CPU. -Andi