Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751197AbWCaCfD (ORCPT ); Thu, 30 Mar 2006 21:35:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751194AbWCaCfD (ORCPT ); Thu, 30 Mar 2006 21:35:03 -0500 Received: from mga02.intel.com ([134.134.136.20]:14739 "EHLO orsmga101-1.jf.intel.com") by vger.kernel.org with ESMTP id S1751191AbWCaCfA (ORCPT ); Thu, 30 Mar 2006 21:35:00 -0500 X-IronPort-AV: i="4.03,148,1141632000"; d="scan'208"; a="17464615:sNHT18378983" Message-Id: <200603310234.k2V2Ysg28086@unix-os.sc.intel.com> From: "Chen, Kenneth W" To: "'Christoph Lameter'" Cc: "Nick Piggin" , "Zoltan Menyhart" , "Boehm, Hans" , "Grundler, Grant G" , , , Subject: RE: Synchronizing Bit operations V2 Date: Thu, 30 Mar 2006 18:35:38 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook, Build 11.0.6353 Thread-Index: AcZUY70vkSR25yrdRLCObMU7G2dxUQAB90oQ In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1264 Lines: 34 Christoph Lameter wrote on Thursday, March 30, 2006 5:38 PM > > Christoph Lameter wrote on Thursday, March 30, 2006 5:13 PM > > > Then there will no barrier since clear_bit only has acquire semantics. > > > This is a bug in bit operations since smb_mb__before_clear_bit does > > > not work as documentted. > > > > Well, please make up your mind with: > > > > Option (1): > > > > #define clear_bit clear_bit_mode(..., RELEASE) > > #define Smp_mb__before_clear_bit do { } while (0) > > #define Smp_mb__after_clear_bit smp_mb() > > > > Or option (2): > > > > #define clear_bit clear_bit_mode(..., ACQUIRE) > > #define Smp_mb__before_clear_bit smp_mb() > > #define Smp_mb__after_clear_bit do { } while (0) > > > > I'm fine with either one. > > Neither one is correct because there will always be one combination of > clear_bit with these macros that does not generate the required memory > barrier. Can you give an example? Which combination? - Ken - 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/