Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758405AbWK0Q4q (ORCPT ); Mon, 27 Nov 2006 11:56:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758404AbWK0Q4q (ORCPT ); Mon, 27 Nov 2006 11:56:46 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:15589 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1758403AbWK0Q4p (ORCPT ); Mon, 27 Nov 2006 11:56:45 -0500 Date: Mon, 27 Nov 2006 16:56:43 +0000 From: Christoph Hellwig To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, Christoph Hellwig , Andrew Morton , Ingo Molnar , Greg Kroah-Hartman , Thomas Gleixner , Tom Zanussi , Karim Yaghmour , Paul Mundt , Jes Sorensen , Richard J Moore , "Martin J. Bligh" , Michel Dagenais , Douglas Niehaus , ltt-dev@shafik.org, systemtap@sources.redhat.com Subject: Re: [PATCH 4/16] LTTng 0.6.36 for 2.6.18 : atomic UP operations on SMP Message-ID: <20061127165643.GD5348@infradead.org> Mail-Followup-To: Christoph Hellwig , Mathieu Desnoyers , linux-kernel@vger.kernel.org, Andrew Morton , Ingo Molnar , Greg Kroah-Hartman , Thomas Gleixner , Tom Zanussi , Karim Yaghmour , Paul Mundt , Jes Sorensen , Richard J Moore , "Martin J. Bligh" , Michel Dagenais , Douglas Niehaus , ltt-dev@shafik.org, systemtap@sources.redhat.com References: <20061124215518.GE25048@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061124215518.GE25048@Krystal> User-Agent: Mutt/1.4.2.2i X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 949 Lines: 17 On Fri, Nov 24, 2006 at 04:55:18PM -0500, Mathieu Desnoyers wrote: > This patch adds a UP flavor of SMP operations which is intended to provide > atomic modification of per-cpu data without suffering from the LOCK of memory > barrier performance cost. Note that extreme care must be taken when accessing > this data from different CPUs : smp_wmb() and smp_rmb() must be used > explicitely. As this last scenario happens very rarely in LTTng, it provides a We already have local_t in asm/local.h for this purposed. Unfortunately several architecture implementations are rather suboptimal, but I'm sure the architecture maintainers would be interested in patches to optimize the various implementations. - 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/