Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757475Ab1FFPI0 (ORCPT ); Mon, 6 Jun 2011 11:08:26 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:42133 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164Ab1FFPIY (ORCPT ); Mon, 6 Jun 2011 11:08:24 -0400 Date: Mon, 6 Jun 2011 17:08:08 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Arne Jansen , Linus Torvalds , mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, efault@gmx.de, npiggin@kernel.dk, akpm@linux-foundation.org, frank.rowand@am.sony.com, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages Message-ID: <20110606150808.GF30348@elte.hu> References: <4DEBB05C.8090506@die-jansens.de> <4DEBB3DA.8060001@die-jansens.de> <20110605172052.GA1036@elte.hu> <4DEBBFF9.2030101@die-jansens.de> <20110605185957.GA3452@elte.hu> <4DEBD95B.6030901@die-jansens.de> <20110605194419.GA12965@elte.hu> <4DEBE3DF.70104@die-jansens.de> <1307350909.2353.7408.camel@twins> <20110606150409.GE30348@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110606150409.GE30348@elte.hu> 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=3.3.1 -2.0 BAYES_00 BODY: Bayes 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 Content-Length: 896 Lines: 24 * Ingo Molnar wrote: > The real fix might be to remove the lockdep_off()/on() call from > printk(), that looks actively evil ... we had to hack through > several layers of side-effects before we found the real bug - so > it's not like the off()/on() made things more robust! The other obvious fix would be to *remove* the blasted wakeup from printk(). It's a serious debugging robustness violation and it's not like the wakeup is super important latency-wise. We *already* have a timer tick driven klogd wakeup poll routine. So i doubt we'd have many problems from not doing wakeups from printk(). Opinions? Thanks, 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/