From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 21BF1A0573; Wed, 4 Mar 2020 18:37:54 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 6F99C2C02; Wed, 4 Mar 2020 18:37:53 +0100 (CET) Received: from mail-pl1-f193.google.com (mail-pl1-f193.google.com [209.85.214.193]) by dpdk.org (Postfix) with ESMTP id 8D1963B5 for ; Wed, 4 Mar 2020 18:37:51 +0100 (CET) Received: by mail-pl1-f193.google.com with SMTP id w12so1154404pll.13 for ; Wed, 04 Mar 2020 09:37:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=e7ESP2nfMzLtbcr0DCR45UoX7qTgo0GYvzXEa+g35OY=; b=Vm1w5XcAqwlLX23dz79jodWORxPbvGhA/xZ9WZQ34x0itqVtwyUbwceY7TOM8x7zGP r7V02IAdDMdPzP47xWDTlySY76JEKkx5hV0L1wf/PhhL2pmRyx92zDvHmkiHM+3HGstR 9+7blCHfbO+ieIKbgvIGByk67lUJeUegJMvmSXcgn+M6crswxVEP+0USUbckIvNQiGpb 1f4lSdNLngH6HC2b72w03C3mW2s8wg74inqivmkqiEqyJ+8rOnH+1mlTIdZby83HWn60 z19lFT8+vfaO0akggWqwAV/QflVfGcIWoQAfx1QPl70sZoSSpgWOO5ygN6KF25Ww2k/t lcsw== 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=e7ESP2nfMzLtbcr0DCR45UoX7qTgo0GYvzXEa+g35OY=; b=mmshUGOnS2wMbUq1JNPo1cwMMz3ShQqMR9vXo2gtvXJDHRPQoxDjooBpFm8InDtnGI wddxbZ6+CiHJ3v3QamJB5wsS3Aze2p6+POZeiucLx/oiQd8RYQPCu3JVwqr/6IUJCmNN wW/lAguhQhBKYDkZVbXkHiobbP/PcuXaYX+iOnZUSr+1w5xFZN+b5/O+yuFxuGFzP9GZ JmAMFKfwhxyOl0yMQdV2WH3k3I8AqwOS9YVE0bYhaMbnEFej8Oin2hwBBVKJwhXqkf9b 2xBKKJD7VT0ii4fBnC4uZmOFNmAMKTTuzDC6C9xPP1dnNZzLD0J58XuZa4MlKEtLRYob JIQA== X-Gm-Message-State: ANhLgQ1REOROD5uNTS0SEL4isrqUSEOlxNKn6BEzj5k3bF6MUojCXT5G RToBb1kmYiB/D5io2pNg1/YHdw== X-Google-Smtp-Source: ADFU+vs3HPmC+Jb2KflqrnwTBBYgbrJMmROEQXLm4Q3zIahVBUQ0fXx4cK49sZbQc/Fyovx8aA8Yyw== X-Received: by 2002:a17:90a:654a:: with SMTP id f10mr4160443pjs.50.1583343470558; Wed, 04 Mar 2020 09:37:50 -0800 (PST) Received: from hermes.lan (204-195-22-127.wavecable.com. [204.195.22.127]) by smtp.gmail.com with ESMTPSA id z6sm4218875pfq.39.2020.03.04.09.37.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2020 09:37:50 -0800 (PST) Date: Wed, 4 Mar 2020 09:37:47 -0800 From: Stephen Hemminger To: "=?UTF-8?B?dGd3X3RlYW0=?=(=?UTF-8?B?6IW+6K6v572R5YWz5Zui6Zif?=)" Cc: Tencent TGW team , Thomas Monjalon , Ferruh Yigit , Andrew Rybchenko , "dev@dpdk.org" Message-ID: <20200304093747.64f1f251@hermes.lan> In-Reply-To: References: <20200304140543.31612-1-tgw_team@tencent.com> <20200304081509.072c9d3b@hermes.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [dpdk-dev] [PATCH] rte_ethdev: fix unsafe memory access by calling RX callback.(Internet mail) X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Wed, 4 Mar 2020 16:38:13 +0000 tgw_team(=E8=85=BE=E8=AE=AF=E7=BD=91=E5=85=B3=E5=9B=A2=E9=98=9F) wrote: > Sorry, I`ll use a real name in patch v2. >=20 > I don't think this is a TOCTOU question. > The original code works fine when compiled with the -O3 option. > At this point the compiler will optimize to one memory access. > But when compiled with -O0, there will be two memory accesses, which is w= rong. > This change was modified with reference to the rte_eth_tx_burst function. There is nothing C standard that says compiler has to do it either way. The optimizer may decide to do two memory accesses or one. Depending on that in anyway is bad practice.