From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755127Ab3H3DQ2 (ORCPT ); Thu, 29 Aug 2013 23:16:28 -0400 Received: from g1t0027.austin.hp.com ([15.216.28.34]:42633 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752074Ab3H3DQ1 (ORCPT ); Thu, 29 Aug 2013 23:16:27 -0400 Message-ID: <52200E7C.5040402@hp.com> Date: Thu, 29 Aug 2013 23:16:12 -0400 From: Waiman Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12 MIME-Version: 1.0 To: Alexander Fyodorov CC: linux-kernel , "Chandramouleeswaran, Aswin" , "Norton, Scott J" , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Ingo Molnar Subject: Re: [PATCH RFC v2 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation References: <15321377012704@web8h.yandex.ru> <52142D6C.6000400@hp.com> <336901377100289@web16f.yandex.ru> <5215638E.5020702@hp.com> <169431377178121@web21f.yandex.ru> <521BB71F.6080300@hp.com> <66111377605355@web12m.yandex.ru> <521F67C9.4080805@hp.com> <53161377795800@web14m.yandex.ru> In-Reply-To: <53161377795800@web14m.yandex.ru> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/29/2013 01:03 PM, Alexander Fyodorov wrote: > 29.08.2013, 19:25, "Waiman Long": >> What I have been thinking is to set a flag in an architecture specific >> header file to tell if the architecture need a memory barrier. The >> generic code will then either do a smp_mb() or barrier() depending on >> the presence or absence of the flag. I would prefer to do more in the >> generic code, if possible. > If you use flag then you'll have to check it manually. It is better to add new smp_mb variant, I suggest calling it smp_mb_before_store(), and define it to barrier() on x86. I am sorry that I was not clear in my previous mail. I mean a flag/macro for compile time checking rather than doing runtime checking. Regards, Longman