Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758069AbYBKPjV (ORCPT ); Mon, 11 Feb 2008 10:39:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757528AbYBKPi5 (ORCPT ); Mon, 11 Feb 2008 10:38:57 -0500 Received: from mx1.redhat.com ([66.187.233.31]:52844 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757518AbYBKPi4 (ORCPT ); Mon, 11 Feb 2008 10:38:56 -0500 Message-ID: <47B06BBD.4050306@redhat.com> Date: Mon, 11 Feb 2008 10:37:33 -0500 From: Steven Rostedt User-Agent: Thunderbird 1.5.0.12 (X11/20071019) MIME-Version: 1.0 To: Heiko Carstens CC: "Paul E. McKenney" , Gautham R Shenoy , Dipankar Sarma , Ingo Molnar , Martin Schwidefsky , linux-kernel@vger.kernel.org Subject: Re: preempt rcu bug on s390 References: <20080209113435.GA6915@osiris.boeblingen.de.ibm.com> <20080209140711.GA16205@linux.vnet.ibm.com> <20080209171451.GB8069@osiris.ibm.com> <20080209220226.GB16205@linux.vnet.ibm.com> <20080210130150.GA9044@osiris.ibm.com> In-Reply-To: <20080210130150.GA9044@osiris.ibm.com> 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: 1319 Lines: 33 Heiko Carstens wrote: >> Does s390 start out in nohz mode? The reason I ask is that it feels like >> an off-by-one error for the dynticks_progress_counter. > > Actually I forgot to add a few ifdefs to make the code do something :) > That just reveals that we have a conflict with the dynticks implementation > and s390's nohz that shows up in what rcu_irq_enter/exit assume. > I didn't patch s390 and common code so it will work, but I think the > patch you mentionened will fix the problem I reported. > So I guess we should either convert s390 to use the generic dynticks > implementation or disable preemptible rcu on s390 until we converted > our code. > > Thanks for helping debugging this! Heiko, thanks for reporting this. This patch still didn't make it into -rc1, and it really should. Because without this patch, PREEMPT_RCU and NO_HZ together is broken, on all boxes. The patch is in Ingo's sched-devel git tree, as 9460545f81ea48b07dbb20456a8ede776d8ebc1b (last I checked) and titled: rcu: add support for dynamic ticks and preempt rcu -- Steve -- 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/