From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754841Ab0CNHAQ (ORCPT ); Sun, 14 Mar 2010 03:00:16 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:58436 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754349Ab0CNHAM (ORCPT ); Sun, 14 Mar 2010 03:00:12 -0400 Date: Sun, 14 Mar 2010 07:59:52 +0100 From: Ingo Molnar To: Linus Torvalds , Peter Zijlstra , Thomas Gleixner Cc: "Eric W. Biederman" , Jiri Kosina , Larry Finger , WANG Cong , Greg Kroah-Hartman , Tejun Heo , Linux Kernel Mailing List Subject: Re: [PATCH] base firmware: Fix BUG from sysfs attributes change in commit a2db6842873c8e5a70652f278d469128cb52db70 Message-ID: <20100314065952.GA24489@elte.hu> References: <4b9be956.x5+yAHXGDfXer810%Larry.Finger@lwfinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 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 * Linus Torvalds wrote: > On Sat, 13 Mar 2010, Eric W. Biederman wrote: > > > > It also only affects those fairly rare lockdep users as well, and the only > > affect is to throw a nasty warning message. Isn't lockdep all about throwing > > nasty warning messages? > > Hmm. The report has that "BUG: " message in it (and in the subject line), > but you're right - it ends up being just a warning, not actually a real > BUG() (which is a machine killer). > > So yeah - it's not as bad as I thought. Sorry. > > [ And that "BUG:" in turn seems to be due to Ingo for some reason wanting > to confuse BUG_ON() messages (which have that "BUG: " prefix thing) with > whatever warning conditions he adds. > > Our warnings used to have that bug too (see commit 8f53b6fcc4: "Don't > call a warnign a bug. It's a warning."). > > Ingo: can we agree to not put "BUG: " messages in warnings, ok? It may > be a bug (lower-case) that triggers them, but that whole "BUG()" thing > has it's own semantics with rather more serious consequences than some > warning that lets things continue. Sure - will change those too over to the "INFO: " pattern we've been using for some time. All new warnings that come via our trees use 'INFO: ', the 'BUG: ' ones are there for historic reasons. There's a few that are external to lockdep and are likely fatal conditions: printk( "[ BUG: bad unlock balance detected! ]\n"); printk( "[ BUG: bad contention detected! ]\n"); printk( "[ BUG: held lock freed! ]\n"); printk( "[ BUG: lock held at task exit time! ]\n"); (these things often tend to cause hangs/crashes later on.) and then there's a few that are mostly internal to lockdep, and should never be fatal: printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n"); printk("BUG: MAX_LOCKDEP_KEYS too low!\n"); printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n"); printk("BUG: MAX_LOCKDEP_CHAINS too low!\n"); printk("BUG: key %p not in .data!\n", key); printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n"); printk("BUG: MAX_LOCK_DEPTH too low!\n"); [ there's rare exceptions - i've seen 'BUG: key' + real crash on a few occasions, when the warning was caused by memory corruption. But typically the warning is not fatal, and this is what matters to the severity of the message. ] So i'm wondering whether we should/could keep those first four with a 'BUG: ' message, as lockdep wont crash the machine in the BUG() fashion. The other 7 should definitely be less alarming messages. Ingo