From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C68AC433E0 for ; Wed, 27 Jan 2021 23:06:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED79A64DD0 for ; Wed, 27 Jan 2021 23:06:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234428AbhA0XFz (ORCPT ); Wed, 27 Jan 2021 18:05:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:39984 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233556AbhA0XBW (ORCPT ); Wed, 27 Jan 2021 18:01:22 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E95F164DCE; Wed, 27 Jan 2021 22:22:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611786167; bh=XlDDbXd58PRQLQnVBVMxsMBxLbjIOdstTUlWPOs1plY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FkuVkySLPNkaRm8Qzv68SuVxwtHoJVIUTGuN7vBFH6O788iez+gbUX74iv6iaQV2Z DUH/rqf/I4cYO6BTBoThYav/tey+78ZfnB2Daw0heFFnmKmDPb68LtQYjMOf9O0Z9l McbmPCoO/m4Vk5287UPDWGjwXuuDiyNYiXtjUlQ3OdTz4JFQ0rtL/q1PKA4Dgr60/2 PfH6jWxW4KT/6WbtwyhruADXCJmmbciW9sZGh/qWHnH3IxqwDskoTjNcx+WJoCE1QZ kszf8ogtK5X5Gx9xssXhB2UbTTwGAzj8uiHNRQN1nB3aVc1AfvZYIN0xGtJVGDtnIm JM7QEHX48cAKw== Date: Wed, 27 Jan 2021 22:22:42 +0000 From: Will Deacon To: Alexander A Sverdlin Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, Russell King , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 2/2] ARM: mcs_spinlock: Drop smp_wmb in arch_mcs_spin_lock_contended() Message-ID: <20210127222241.GC848@willie-the-truck> References: <20210127200109.16412-1-alexander.sverdlin@nokia.com> <20210127200109.16412-2-alexander.sverdlin@nokia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210127200109.16412-2-alexander.sverdlin@nokia.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 27, 2021 at 09:01:09PM +0100, Alexander A Sverdlin wrote: > From: Alexander Sverdlin > > Drop smp_wmb in arch_mcs_spin_lock_contended() after adding in into > ARCH-independent code. > > Signed-off-by: Alexander Sverdlin > --- > arch/arm/include/asm/mcs_spinlock.h | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/arm/include/asm/mcs_spinlock.h b/arch/arm/include/asm/mcs_spinlock.h > index 529d2cf..d8fa921 100644 > --- a/arch/arm/include/asm/mcs_spinlock.h > +++ b/arch/arm/include/asm/mcs_spinlock.h > @@ -8,8 +8,6 @@ > /* MCS spin-locking. */ > #define arch_mcs_spin_lock_contended(lock) \ > do { \ > - /* Ensure prior stores are observed before we enter wfe. */ \ > - smp_mb(); \ I think this is the right place for the barrier, not in the core code. Will