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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 348B4C54F70 for ; Sun, 19 Apr 2020 19:00:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11DF42072B for ; Sun, 19 Apr 2020 19:00:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=konsulko.com header.i=@konsulko.com header.b="Gn5ICBZn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726606AbgDSTAd (ORCPT ); Sun, 19 Apr 2020 15:00:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726440AbgDSTAd (ORCPT ); Sun, 19 Apr 2020 15:00:33 -0400 Received: from mail-wm1-x344.google.com (mail-wm1-x344.google.com [IPv6:2a00:1450:4864:20::344]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A73C9C061A0C for ; Sun, 19 Apr 2020 12:00:32 -0700 (PDT) Received: by mail-wm1-x344.google.com with SMTP id e26so8486928wmk.5 for ; Sun, 19 Apr 2020 12:00:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=konsulko.com; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=dbguNHWcX0WpD8Qi2EDyD45Mg2CX3DqqIAhxCK3ggM4=; b=Gn5ICBZna8X/ikaXqhylt5bvcKKmxKDftFrwJbsRy/c75GlY+hA1hKt/xacUGJG6Hy //ghE1nPj6WPlOew2yRBuSiDiKNbHd9EZVMQD2sQ9nJxzBlBskoasVPxs4X+mT8ZunVr 3iQc4nQ+vP7IhQSmHR0anIGuUSqqLT9yXB3ro= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=dbguNHWcX0WpD8Qi2EDyD45Mg2CX3DqqIAhxCK3ggM4=; b=R193LTEQ40SZi9iAgT6ooFRnQHx0iNAdHNqCaFuzxAnVO0AVtTzyoYHMzeDplXyxlM VKcBZCUfBBQNhRSlAV7IFlWxQoVb2kWoY4r7c4KzYJu43npcaCwRMuHGrNlQhd0HXFaA WhXNsOp7j47tNRSquvEzeX711CbcP3X8rNMyJXPgM1LQOfneR0oDfQ8yqOSPnSS3+jgi Voy69ip6jVgWxYF+4+CCWYPnIqSeqYj4L4QW2XJOuLdeZ000YzW/3SmRzRJWvoWLrAsC jtIArSrLHlz1IFsgBrYTpHYaudlPJcoqF/QUOPvgIrsyJc4nvTCWF2T/+ZQ0rUTeUxij vSSg== X-Gm-Message-State: AGi0PuYxPf5e4Ep99VbODJOjxWfRYjdM4dUuiRBWeE5wqJCbtVHKJpYt U4TPAU94Kksezgh3OqfoPKe+sw== X-Google-Smtp-Source: APiQypK0Tg8j9I7eoqCF3fHFUvDiIgShrTnT+ccFYA0TQdZ8pvtl29UwlDpF0tfmHbpPlWgvb3Eeuw== X-Received: by 2002:a1c:1f8e:: with SMTP id f136mr13394292wmf.166.1587322831285; Sun, 19 Apr 2020 12:00:31 -0700 (PDT) Received: from carbon ([94.26.108.4]) by smtp.gmail.com with ESMTPSA id x13sm16974899wmc.5.2020.04.19.12.00.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 19 Apr 2020 12:00:30 -0700 (PDT) Date: Sun, 19 Apr 2020 22:00:29 +0300 From: Petko Manolov To: Heiner Kallweit Cc: Realtek linux nic maintainers , David Miller , "netdev@vger.kernel.org" Subject: Re: [PATCH net-next v2 3/3] r8169: use WRITE_ONCE instead of dma_wmb in rtl8169_mark_to_asic Message-ID: <20200419190029.GA37084@carbon> Mail-Followup-To: Heiner Kallweit , Realtek linux nic maintainers , David Miller , "netdev@vger.kernel.org" References: <612105ff-f21d-40c4-2b02-0ac0c12615fb@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <612105ff-f21d-40c4-2b02-0ac0c12615fb@gmail.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 20-04-19 20:16:21, Heiner Kallweit wrote: > We want to ensure that desc->opts1 is written as last descriptor field. > This doesn't require a full compiler barrier, WRITE_ONCE provides the > ordering guarantee we need. > > Signed-off-by: Heiner Kallweit > --- > drivers/net/ethernet/realtek/r8169_main.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c > index 2fc65aca3..3e4ed2528 100644 > --- a/drivers/net/ethernet/realtek/r8169_main.c > +++ b/drivers/net/ethernet/realtek/r8169_main.c > @@ -3892,11 +3892,9 @@ static inline void rtl8169_mark_to_asic(struct RxDesc *desc) > { > u32 eor = le32_to_cpu(desc->opts1) & RingEnd; > > - desc->opts2 = 0; > - /* Force memory writes to complete before releasing descriptor */ > - dma_wmb(); If dma_wmb() was really ever needed here you should leave it even after you order these writes with WRITE_ONCE(). If not, then good riddance. Just saying, i am not familiar with the hardware nor with the driver. :) Petko > - > - desc->opts1 = cpu_to_le32(DescOwn | eor | R8169_RX_BUF_SIZE); > + /* Ensure ordering of writes */ > + WRITE_ONCE(desc->opts2, 0); > + WRITE_ONCE(desc->opts1, cpu_to_le32(DescOwn | eor | R8169_RX_BUF_SIZE)); > } > > static struct page *rtl8169_alloc_rx_data(struct rtl8169_private *tp, > @@ -3919,7 +3917,7 @@ static struct page *rtl8169_alloc_rx_data(struct rtl8169_private *tp, > return NULL; > } > > - desc->addr = cpu_to_le64(mapping); > + WRITE_ONCE(desc->addr, cpu_to_le64(mapping)); > rtl8169_mark_to_asic(desc); > > return data; > -- > 2.26.1 > >