Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757605Ab1EZMu1 (ORCPT ); Thu, 26 May 2011 08:50:27 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:44728 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827Ab1EZMu0 (ORCPT ); Thu, 26 May 2011 08:50:26 -0400 Date: Thu, 26 May 2011 14:50:07 +0200 From: Ingo Molnar To: Russell King - ARM Linux Cc: Peter Zijlstra , Marc Zyngier , Frank Rowand , Oleg Nesterov , linux-kernel@vger.kernel.org, Yong Zhang , linux-arm-kernel@lists.infradead.org Subject: Re: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM Message-ID: <20110526125007.GA27083@elte.hu> References: <1306272750.2497.79.camel@laptop> <1306343335.21578.65.camel@twins> <1306358128.21578.107.camel@twins> <1306405979.1200.63.camel@twins> <1306407759.27474.207.camel@e102391-lin.cambridge.arm.com> <1306409575.1200.71.camel@twins> <1306412511.1200.90.camel@twins> <20110526122623.GA11875@elte.hu> <20110526123137.GG24876@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110526123137.GG24876@n2100.arm.linux.org.uk> 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: 1046 Lines: 29 * Russell King - ARM Linux wrote: > On Thu, May 26, 2011 at 02:26:23PM +0200, Ingo Molnar wrote: > > > > * Peter Zijlstra wrote: > > > > > Sort this by reverting to the old behaviour for this situation > > > and perform a full remote wake-up. > > > > Btw., ARM should consider switching most of its subarchitectures > > to !__ARCH_WANT_INTERRUPTS_ON_CTXSW - enabling irqs during > > context switches is silly and now expensive as well. > > Not going to happen. The reason we do it is because most of the > CPUs have to (slowly) flush their caches during switch_mm(), and to > have IRQs off over the cache flush means that we lose IRQs. How much time does that take on contemporary ARM hardware, typically (and worst-case)? 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/