From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757463Ab0DOHdO (ORCPT ); Thu, 15 Apr 2010 03:33:14 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:44528 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757357Ab0DOHdJ (ORCPT ); Thu, 15 Apr 2010 03:33:09 -0400 Date: Thu, 15 Apr 2010 09:32:56 +0200 From: Ingo Molnar To: David Miller Cc: sfr@canb.auug.org.au, tglx@linutronix.de, hpa@zytor.com, peterz@infradead.org, linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, fweisbec@gmail.com, linuxppc-dev@lists.ozlabs.org Subject: Re: linux-next: PowerPC WARN_ON_ONCE() after merge of the final tree (tip related) Message-ID: <20100415073256.GG9240@elte.hu> References: <20100415161214.04637496.sfr@canb.auug.org.au> <20100415064940.GA9240@elte.hu> <20100414.235557.123118153.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100414.235557.123118153.davem@davemloft.net> 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 * David Miller wrote: > From: Ingo Molnar > Date: Thu, 15 Apr 2010 08:49:40 +0200 > > > Btw., WARN_ON trapping on PowerPC is clearly a PowerPC bug - there's a good > > reason we have WARN_ON versus BUG_ON - it should be fixed. > > I disagree, an implementation should be allowed to use the most > efficient implementation possible for both interfaces. It trades robustness for slightly better space/code efficiency. Such a trap based mechanism exists on x86 as well and we use it for BUG_ON(). We intentionally dont use it to generate warnings and dont override __WARN(), because it would blow up way too often when a warning triggers in some sensitive codepath that cannot take a trap. Anyway, the warning obviously has to be fixed - but the boot crash itself is PowerPC's own doing. Ingo