Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756036Ab1FEL6A (ORCPT ); Sun, 5 Jun 2011 07:58:00 -0400 Received: from mo-p00-ob.rzone.de ([81.169.146.161]:49819 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753646Ab1FEL57 (ORCPT ); Sun, 5 Jun 2011 07:57:59 -0400 X-RZG-AUTH: :IGUXYVOIf/Z0yAghYbpIhzghmj8icP68r1arC3zTx2B9G7/X5zri/u5Y1+fsZ6BmRA== X-RZG-CLASS-ID: mo00 Message-ID: <4DEB6F3A.3000109@die-jansens.de> Date: Sun, 05 Jun 2011 13:57:46 +0200 From: Arne Jansen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.17) Gecko/20110424 Thunderbird/3.1.10 MIME-Version: 1.0 To: Ingo Molnar CC: Peter Zijlstra , 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 References: <1307092535.2353.2973.camel@twins> <4DE8B13D.9020302@die-jansens.de> <1307097052.2353.3061.camel@twins> <20110605081747.GA17920@elte.hu> <4DEB4FA7.3050400@die-jansens.de> <20110605095555.GA22058@elte.hu> <4DEB58D8.4000805@die-jansens.de> <20110605110132.GB23463@elte.hu> <20110605111933.GA24592@elte.hu> <20110605113627.GA25724@elte.hu> In-Reply-To: <20110605113627.GA25724@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 50 On 05.06.2011 13:36, Ingo Molnar wrote: > > * Ingo Molnar wrote: > >>> If the ticks stop this suggests a lockup within the printk code. >>> [...] >> >> In which case the printk-killswitch patch below (to be applied >> *instead* of the previous debugging patch i sent) should provide >> the desired NMI watchdog output on the serial console. >> >> Warning: it's entirely untested. How is the output supposed to come through? shouldn't printk revert to early_printk instead of just returning? > > Note, since this is an SMP box, if the lockup messages show up with > this patch but are mixed up with each other then adding a spinlock > around the WARN() would probably help keeping the output serialized. > > A simple: > > static DEFINE_SPINLOCK(watchdog_output_lock); > > ... > spin_lock(&watchdog_output_lock); > ... > [ the WARN_ON() logic. ] > ... > spin_unlock(&watchdog_output_lock); > ... > > would suffice. > > 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/ -- 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/