Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760325AbWLFIzp (ORCPT ); Wed, 6 Dec 2006 03:55:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760330AbWLFIzp (ORCPT ); Wed, 6 Dec 2006 03:55:45 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:44888 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760325AbWLFIzo (ORCPT ); Wed, 6 Dec 2006 03:55:44 -0500 Date: Wed, 6 Dec 2006 09:54:28 +0100 From: Ingo Molnar To: Jiri Kosina Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] let WARN_ON() output the condition Message-ID: <20061206085428.GA28160@elte.hu> References: <20061206083730.GB24851@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=no SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1829 Lines: 43 * Jiri Kosina wrote: > On Wed, 6 Dec 2006, Ingo Molnar wrote: > > > a WARN_ON() also triggers a stack dump, which should pinpoint the exact > > location. (especially if combined with kallsyms) For example: > > Actually, I was referring to something a little bit different. For example > kernel/mutex.c:__mutex_lock_common() calls spin_lock_mutex() on line 132. > spin_lock_mutex() contains > > DEBUG_LOCKS_WARN_ON(in_interrupt()); \ > local_irq_save(flags); \ > __raw_spin_lock(&(lock)->raw_lock); \ > DEBUG_LOCKS_WARN_ON(l->magic != l); \ > > When one of these two WARN_ONs trigger, we get only > > WARNING at kernel/mutex.c:132 __mutex_lock_common() no, that's not all we get - we should also get a stackdump. Are you not getting a stackdump perhaps? but i agree with you in theory that your proposed output is better, but the side-effect issue is a killer i think. Could you try to rework it to not evaluate the condition twice and to make it dependent on CONFIG_DEBUG_BUGVERBOSE? You can avoid the evaluation side-effect issue by doing something like: int __c = (c); \ \ if (unlikely(__c)) { \ if (debug_locks_off()) \ WARN_ON(__c); \ __ret = 1; \ Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/