Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753568Ab2BBIoQ (ORCPT ); Thu, 2 Feb 2012 03:44:16 -0500 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:46283 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752980Ab2BBIoO (ORCPT ); Thu, 2 Feb 2012 03:44:14 -0500 Date: Thu, 2 Feb 2012 08:43:50 +0000 From: Russell King - ARM Linux To: TAO HU Cc: Don Zickus , Ingo Molnar , linux-omap , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: In many cases softlockup can not be reported after disabling IRQ for long time Message-ID: <20120202084350.GB1275@n2100.arm.linux.org.uk> References: <20120131154748.GA5650@redhat.com> <20120201145802.GF5650@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1030 Lines: 24 .sdrawkcab esra s'ti ,tsop pot t'noD (Don't top post, it's arse backwards.) On Thu, Feb 02, 2012 at 04:17:02PM +0800, TAO HU wrote: > My concern is not actually that the softlockup could not be reported > while the IRQ is disabled. > What bothering me is that even AFTER re-enable the IRQ, it will not > give warning in many cases. That's already been explained. softlockups are detected by time passing. Time can't properly advance with interrupts disabled, as the backing counter (assuming you're using the clocksource and clockevent stuff) could wrap. If it wraps, the systems idea of time which has passed will be incorrect. So, if interrupts are disabled for a long period, the system loses track of time, and therefore can't know how long the system has been blocked for. -- 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/