Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753780AbaAWRPl (ORCPT ); Thu, 23 Jan 2014 12:15:41 -0500 Received: from mail-vc0-f169.google.com ([209.85.220.169]:55455 "EHLO mail-vc0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752175AbaAWRPj (ORCPT ); Thu, 23 Jan 2014 12:15:39 -0500 MIME-Version: 1.0 In-Reply-To: <52E14D67.4000202@hp.com> References: <1390426438-31252-1-git-send-email-Waiman.Long@hp.com> <1390426438-31252-2-git-send-email-Waiman.Long@hp.com> <20140123100751.GS30183@twins.programming.kicks-ass.net> <52E14D67.4000202@hp.com> Date: Thu, 23 Jan 2014 09:15:38 -0800 X-Google-Sender-Auth: DHfwhUOy8p87kL6q0YJM5iOvtX4 Message-ID: Subject: Re: [PATCH v10 1/4] qrwlock: A queue read/write lock implementation From: Linus Torvalds To: Waiman Long Cc: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Arnd Bergmann , "linux-arch@vger.kernel.org" , "the arch/x86 maintainers" , Linux Kernel Mailing List , Steven Rostedt , Andrew Morton , Michel Lespinasse , Andi Kleen , Rik van Riel , "Paul E. McKenney" , Raghavendra K T , George Spelvin , Tim Chen , "Chandramouleeswaran, Aswin" , Scott J Norton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 23, 2014 at 9:12 AM, Waiman Long wrote: > > I thought that all atomic RMW instructions are memory barrier. On x86 they are. Not necessarily elsewhere. > If they are not, what kind of barrier should be added? smp_mb__before_atomic_xyz() and smp_mb__after_atomic_xyz() will do it, and are no-op (well, barriers - I don't think it matters) on x86. Linus -- 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/