Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263045AbVCXFf2 (ORCPT ); Thu, 24 Mar 2005 00:35:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263044AbVCXFf1 (ORCPT ); Thu, 24 Mar 2005 00:35:27 -0500 Received: from mx2.elte.hu ([157.181.151.9]:19624 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S263037AbVCXFfN (ORCPT ); Thu, 24 Mar 2005 00:35:13 -0500 Date: Thu, 24 Mar 2005 06:34:56 +0100 From: Ingo Molnar To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Esben Nielsen Subject: Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07 Message-ID: <20050324053456.GA14494@elte.hu> References: <20050321090622.GA8430@elte.hu> <20050322054345.GB1296@us.ibm.com> <20050322072413.GA6149@elte.hu> <20050322092331.GA21465@elte.hu> <20050322093201.GA21945@elte.hu> <20050322100153.GA23143@elte.hu> <20050322112856.GA25129@elte.hu> <20050323061601.GE1294@us.ibm.com> <20050323063317.GB31626@elte.hu> <20050324052854.GA1298@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050324052854.GA1298@us.ibm.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 868 Lines: 20 * Paul E. McKenney wrote: > Now, it is true that CPU#2 might record a quiescent state during this > time, but this will have no effect because -all- CPUs must pass > through a quiescent state before any callbacks will be invoked. Since > CPU#1 is refusing to record a quiescent state, grace periods will be > blocked for the full extent of task 1's RCU read-side critical > section. ok, great. So besides the barriers issue (and the long grace period time issue), the current design is quite ok. And i think your original flip pointers suggestion can be used to force synchronization. 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/