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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 0FA73C433E6 for ; Wed, 2 Sep 2020 07:33:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C26FC2087D for ; Wed, 2 Sep 2020 07:32:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="asYSOntc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726948AbgIBHc7 (ORCPT ); Wed, 2 Sep 2020 03:32:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33158 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726674AbgIBHcv (ORCPT ); Wed, 2 Sep 2020 03:32:51 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 536C5C061244; Wed, 2 Sep 2020 00:32:51 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id z1so4098230wrt.3; Wed, 02 Sep 2020 00:32:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=Fu3rhVbErwAPlE8HPpQ0/XopyDhWlhtlly/dcplP9TY=; b=asYSOntcpTHbiaWRo5xy57HdA7Q4MiRosi3KKd0vtdcHs+yGUqusZnzNGmOqfZ8UVf 6kXz4tuOY+SGEyqddBhVB4MTxerGCGnYNQ4pbeUgOB4tH8z4AkWrJLXk0X0EN5ZZhVRo 4FDBQOgCK53ePYGEpP9fkEcsJgQz09Qhhe0ICcbGr2BTa6+7lkVvbqfSI85YfPloxlPB MnbtLSAaY/14jtW1WzmLFfFA1FC/5T3E3nJX59YQXHQJx5YDx9edz8T/m6e2T1eW9LGJ ESkRcp6s9ttPE3lesTIMVIQhbRD2noNFyNERbpTZjSiMDnGIc6oz8waJE994SiJRS67p LyYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=Fu3rhVbErwAPlE8HPpQ0/XopyDhWlhtlly/dcplP9TY=; b=oZEy4LJqdaWDk7JPEzzZ3ZVhPKkucOgaxWcZr5xfNqVi7b60zJO+HElz2Y7dLDGTTl TZ5xF0zuHoDqlMfnhkhvjiBheTWS4I8Q0E6F+9pIZ9B5ZCc3qOSxMYC2MnHWaa4fR0rL jOcBaJdtS1TRSdWingl8cxW4Zux9vqYRkvAqx8BXfv1zLP2ZKT6EUzVRSBrqVMDtvG4w HLO+VoplBlToRcWsgHVi7r4ERfqsd2ikkOguTh5v3xsrdv5fOSG0bynasyztFYibKcfI r+rdR0IFSGJ9MWDvpD+LMh5V3Eicl3B45DDWnMmhUCPZ2MOb0lutb52CYB5/T922sOKu fmeA== X-Gm-Message-State: AOAM531bJQJxYaeYI1UYWJfLVWiwrjCX1Om+Bi6f/Rww3KSaT8UTRTKG ERJ1eydHHAb2Rjc+Wx+LVDsg0EkuHEU= X-Google-Smtp-Source: ABdhPJyDz94/oQIHXyFLv2/XsyDNLzEbN5UnuHyknZu35SS+jOuC0ccqA4JyJdQA1JXBl/6NlmYMaQ== X-Received: by 2002:adf:91c2:: with SMTP id 60mr1633124wri.292.1599031970119; Wed, 02 Sep 2020 00:32:50 -0700 (PDT) Received: from [192.168.8.147] ([37.170.201.185]) by smtp.gmail.com with ESMTPSA id n124sm5126104wmn.29.2020.09.02.00.32.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Sep 2020 00:32:49 -0700 (PDT) Subject: Re: [PATCH net-next] net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc To: Yunsheng Lin , Cong Wang Cc: Jamal Hadi Salim , Jiri Pirko , David Miller , Jakub Kicinski , Linux Kernel Network Developers , LKML , linuxarm@huawei.com References: <1598921718-79505-1-git-send-email-linyunsheng@huawei.com> <511bcb5c-b089-ab4e-4424-a83c6e718bfa@huawei.com> From: Eric Dumazet Message-ID: <1f7208e6-8667-e542-88dd-bd80a6c59fd2@gmail.com> Date: Wed, 2 Sep 2020 09:32:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/1/20 11:34 PM, Yunsheng Lin wrote: > > I am not familiar with TCQ_F_CAN_BYPASS. > From my understanding, the problem is that there is no order between > qdisc enqueuing and qdisc reset. Thw qdisc_reset() should be done after rcu grace period, when there is guarantee no enqueue is in progress. qdisc_destroy() already has a qdisc_reset() call, I am not sure why qdisc_deactivate() is also calling qdisc_reset()