From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759086AbZA2PH2 (ORCPT ); Thu, 29 Jan 2009 10:07:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754695AbZA2PHR (ORCPT ); Thu, 29 Jan 2009 10:07:17 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:55653 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753854AbZA2PHP (ORCPT ); Thu, 29 Jan 2009 10:07:15 -0500 Date: Thu, 29 Jan 2009 16:07:01 +0100 From: Ingo Molnar To: "Rafael J. Wysocki" Cc: =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Steven Rostedt , Linus Torvalds , Maciej Rutecki , Linux Kernel Mailing List , Andrew Morton , Thomas Gleixner Subject: Re: [Linux 2.6.29-rc2] BUG: using smp_processor_id() in preemptible Message-ID: <20090129150701.GE6512@elte.hu> References: <8db1092f0901170058k325dc6ddtddb42deea1ddd098@mail.gmail.com> <200901271628.54037.rjw@sisk.pl> <20090127154946.GA28209@elte.hu> <200901272218.39608.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200901272218.39608.rjw@sisk.pl> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Rafael J. Wysocki wrote: > On Tuesday 27 January 2009, Ingo Molnar wrote: > > > > * Rafael J. Wysocki wrote: > > > > > > In fact whatever check you put in it's _always_ going to be > > > > fundamentally more fragile than direct instrumentation: you cannot > > > > possibly check all possible places that enable interrupts. (they could > > > > be disabling interrupts as a _restore_irqs() sequence for example) > > > > > > In this particular case, I'm not really interested in that. What I'm > > > interested in is which driver's ->suspend_late() or ->resume_early() (or > > > the equivalents for sysdevs) has enabled interrupts, which is quite easy > > > to check directly. > > > > But this is exactly what it does - without any need for debug checks > > spread around! > > > > You'll get a _full stack dump_ from the very driver that is enabling > > interrupts! You dont get a trace - you get a stack dump of the very place > > that is buggy. It does not get any better than that. > > I'm not going to argue. > > Nevertheless, IMO something like the patch below should be sufficient to catch > these bugs. > > Thanks, > Rafael > > > --- > drivers/base/power/main.c | 12 ++++++++++++ > drivers/base/sys.c | 21 ++++++++++++++++----- > include/linux/pm.h | 18 ++++++++++++++++++ > 3 files changed, 46 insertions(+), 5 deletions(-) hm, so now you sprinkle debug checks all around the code, instead of putting in a single pair of: force_irqs_off_start(); ... force_irqs_off_end(); which would catch everything that your checks would catch - and it would catch more. In what way is your approach better? Ingo