Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756597Ab0LJQvB (ORCPT ); Fri, 10 Dec 2010 11:51:01 -0500 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:59412 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754481Ab0LJQvA (ORCPT ); Fri, 10 Dec 2010 11:51:00 -0500 Date: Fri, 10 Dec 2010 16:50:21 +0000 From: Russell King - ARM Linux To: Peter Zijlstra Cc: Venkatesh Pallipadi , Mikael Pettersson , Ingo Molnar , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, John Stultz Subject: Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM Message-ID: <20101210165021.GA28263@n2100.arm.linux.org.uk> References: <1291917330.6803.7.camel@twins> <1291920939.6803.38.camel@twins> <1291936593.13513.3.camel@laptop> <1291975704.6803.59.camel@twins> <1291987065.6803.151.camel@twins> <1291987635.6803.161.camel@twins> <1291988866.6803.171.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1291988866.6803.171.camel@twins> 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: 1168 Lines: 30 On Fri, Dec 10, 2010 at 02:47:46PM +0100, Peter Zijlstra wrote: > > Full patch.. > > --- > Subject: sched: Fix the irqtime code to deal with u64 wraps > From: Peter Zijlstra > Date: Thu Dec 09 14:15:34 CET 2010 > > ARM systems have a 32bit sched_clock() [ which needs to be fixed ], > but this exposed a bug in the irq_time code as well, it doesn't deal > with wraps at all. > > Fix the irq_time code to deal with u64 wraps by re-writing the code to > only use delta increments, which avoids the whole issue. > > Furthermore, solve the problem of 32bit arches reading partial updates > of the u64 time values. > > Cc: Venkatesh Pallipadi > Reported-by: Russell King - ARM Linux I think credit should go to Mikael Pettersson, who identified the interactivity regression and problematical commit. I only pointed out the dubious nature of the code. -- 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/