Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262861AbVCWIAJ (ORCPT ); Wed, 23 Mar 2005 03:00:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261246AbVCWH7p (ORCPT ); Wed, 23 Mar 2005 02:59:45 -0500 Received: from mx1.elte.hu ([157.181.1.137]:57044 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S261233AbVCWH7V (ORCPT ); Wed, 23 Mar 2005 02:59:21 -0500 Date: Wed, 23 Mar 2005 08:58:54 +0100 From: Ingo Molnar To: Steven Rostedt Cc: "Paul E. McKenney" , linux-kernel@vger.kernel.org, Esben Nielsen Subject: Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07 Message-ID: <20050323075854.GA4348@elte.hu> References: <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> <20050323071604.GA32712@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i 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: 1056 Lines: 24 * Steven Rostedt wrote: > > i think the 'migrate read-count' method is not adequate either, because > > all callbacks queued within an RCU read section must be called after the > > lock has been dropped - while with the migration method CPU#1 would be > > free to process callbacks queued in the RCU read section still active on > > CPU#2. > > Although you can't disable preemption for the duration of the > rcu_readlock, what about pinning the process to a CPU while it has the > lock. Would this help solve the migration issue? yes, but that's rather gross. PREEMPT_BKL was opposed by Linus precisely because it used such a method - once that was fixed, PREEMPT_BKL got accepted. It also limits the execution flow quite much. I'd rather not do it if there's any other method. 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/