Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757697Ab1FFPwy (ORCPT ); Mon, 6 Jun 2011 11:52:54 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:48601 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757480Ab1FFPwx (ORCPT ); Mon, 6 Jun 2011 11:52:53 -0400 Date: Mon, 6 Jun 2011 17:52:36 +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: <20110606155236.GA7374@elte.hu> References: <4DEB6F3A.3000109@die-jansens.de> <20110605133958.GA27812@elte.hu> <4DEB8A93.30601@die-jansens.de> <20110605141003.GB29338@elte.hu> <4DEB933C.1070900@die-jansens.de> <20110605151323.GA30590@elte.hu> <1307349530.2353.7374.camel@twins> <20110606145827.GD30348@elte.hu> <1307372989.2322.136.camel@twins> <1307375227.2322.161.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1307375227.2322.161.camel@twins> 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: 858 Lines: 24 * Peter Zijlstra wrote: > Needs more staring at, preferably by someone who actually > understands that horrid mess :/ Also, this all still doesn't make > printk() work reliably while holding rq->lock. So, what about my suggestion to just *remove* the wakeup from there and use the deferred wakeup mechanism that klogd uses. That would make printk() *visibly* more robust in practice. [ It would also open up the way to possibly make printk() NMI entry safe - currently we lock up if we printk in an NMI or #MC context that happens to nest inside a printk(). ] 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/