From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938170AbZDJNij (ORCPT ); Fri, 10 Apr 2009 09:38:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762743AbZDJNi2 (ORCPT ); Fri, 10 Apr 2009 09:38:28 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:37689 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754579AbZDJNi2 (ORCPT ); Fri, 10 Apr 2009 09:38:28 -0400 Date: Fri, 10 Apr 2009 15:38:14 +0200 From: Ingo Molnar To: Frederic Weisbecker Cc: LKML , Peter Zijlstra Subject: Re: [PATCH 1/2] lockdep: warn about lockdep disabling after kernel taint Message-ID: <20090410133814.GA17878@elte.hu> References: <1239312460-13396-1-git-send-email-fweisbec@gmail.com> <20090410121243.GO21506@elte.hu> <20090410133443.GC5988@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090410133443.GC5988@nowhere> 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 * Frederic Weisbecker wrote: > On Fri, Apr 10, 2009 at 02:12:43PM +0200, Ingo Molnar wrote: > > > > * Frederic Weisbecker wrote: > > > > > Impact: provide useful missing info for developers > > > > > > Kernel taint can occur in several situations such as warnings, > > > load of prorietary or staging modules, bad page, etc... > > > > > > But when such taint happens, a developer might still be working on > > > the kernel, expecting that lockdep is still enabled. But a taint > > > disables lockdep without ever warning about it. > > > Such a kernel behaviour doesn't really help for kernel development. > > > > > > This patch adds this missing warning. > > > > > > Since the taint is done most of the time after the main message that > > > explain the real source issue, it seems safe to warn about it inside > > > add_taint() so that it appears at last, without hurting the main > > > information. > > > > > > Signed-off-by: Frederic Weisbecker > > > > > > diff --git a/kernel/panic.c b/kernel/panic.c > > > index 3fd8c5b..9e7420a 100644 > > > --- a/kernel/panic.c > > > +++ b/kernel/panic.c > > > @@ -213,8 +213,14 @@ unsigned long get_taint(void) > > > > > > void add_taint(unsigned flag) > > > { > > > - /* can't trust the integrity of the kernel anymore: */ > > > - debug_locks = 0; > > > + /* > > > + * Can't trust the integrity of the kernel anymore. > > > + * We don't call directly debug_locks_off() because the issue > > > + * is not necessarily serious enough to set oops_in_progress to 1 > > > + */ > > > + if (xchg(&debug_locks, 0)) > > > + printk(KERN_WARNING "Disabling lockdep due to kernel taint\n"); > > > + > > > > nice idea - but please use the proper debug_locks_off() construct > > instead of an open-coded xchg(). Something like: > > > > if (debug_locks_off()) > > printk(...); > > > > should do the trick. > > > > Ingo > > Yeah, I first wanted to do so but was shy about the > oops_in_progress = 1 inside debug_locks_off(). Isn't it a problem? hm, indeed. How about providing a __debug_locks_off() primitive that only does the xchg and none of the oops_in_progress and console_verbose() calls? Ingo