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=-4.3 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 F0330C433B4 for ; Thu, 15 Apr 2021 06:47:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD3346113D for ; Thu, 15 Apr 2021 06:47:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230477AbhDOGsS (ORCPT ); Thu, 15 Apr 2021 02:48:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229933AbhDOGsR (ORCPT ); Thu, 15 Apr 2021 02:48:17 -0400 Received: from mail-wr1-x433.google.com (mail-wr1-x433.google.com [IPv6:2a00:1450:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4BA62C061574 for ; Wed, 14 Apr 2021 23:47:55 -0700 (PDT) Received: by mail-wr1-x433.google.com with SMTP id m9so9410629wrx.3 for ; Wed, 14 Apr 2021 23:47:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=iCQdv8HoumdliWIWYQS4JumgYscFa/gV1zbXETxIh14=; b=B2MkUL56cNMV2Wi9qkiYMT7W+fp3gYeH1OAKqRAibh6m9lLYSVBS9dUcftDTJxqCK/ uMf0fz/qXjik60mQRVtn7RKPq37jNjMmRmUy9vEMV+shsg85qW+qoPLrjbaQdHeB4Rwz 3wohVkMSajyxlVSqj2IHBBfw25bwsOvpzdS1xSVpLn2UBprIMxlQMf5qwpDxdOyWDcob mT2cCN2jjLPAXkymUQk6rdu+zChldll5/YRm9gdlI53ypgG3Q8OLDtv7ERGydY4hCsbm M9hhBq3Y6F9vr0eeXyS4Hp+e7vsCIv0hasT6olWC2pMHeATVEJg496WVUSonArP7Hkee G/aw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=iCQdv8HoumdliWIWYQS4JumgYscFa/gV1zbXETxIh14=; b=rT8JGSrCe7BAXBmj6+epkWAJoxuYp8HgRPjWQu4p+beVm744PHvc5fkSQQKxo1FJeh /r+G7BqpZgVALIzR2IFCJPfB9irZPqnJV8XdzlVHAwuTskpLy82glKVx+uQ1gpzCYyNi 3h9O4nlQPQfdoGzVJQ7Mk4GTJzI4+aH6gj5rUxj27UG9VGGHQSp83MAim8T39GeUVzZP +AvyTw4KftjReT83RdKjokZ56zXY1lp4K1bxjaeaaonUebwu+GoxyaYZMQpAp+AgM9F2 gUyQKVtOo5h/IulNO9KsXmhBZgPzdvVAzjpL+ke6FBMQ2RvKbq7tFCG1Ep/MmTuOqs2k wgtw== X-Gm-Message-State: AOAM533LCGxxZPEBN+3ENIu0053ER7ePpEqpCgkBXRjRtbTL1Lkk0KJS RVEGI6hsyWJ4sEONQEW6fwpNKSPryv0= X-Google-Smtp-Source: ABdhPJwnD6ZdYtiRJ+3Fi0pyL2wmHfsQieYswynWzhX4QG8BmOMsMmRDF3s6VRwPD7Wq1rO23Voyzw== X-Received: by 2002:adf:ef8b:: with SMTP id d11mr1672499wro.107.1618469273863; Wed, 14 Apr 2021 23:47:53 -0700 (PDT) Received: from [192.168.1.101] ([37.166.86.66]) by smtp.gmail.com with ESMTPSA id b14sm1623025wrf.75.2021.04.14.23.47.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Apr 2021 23:47:53 -0700 (PDT) Subject: Re: [PATCH net v2] net: core: make napi_disable more robust To: Lijun Pan , netdev@vger.kernel.org References: <20210414080845.11426-1-lijunp213@gmail.com> From: Eric Dumazet Message-ID: <1917fb7e-e8e5-a65a-7232-ddd6407fcc53@gmail.com> Date: Thu, 15 Apr 2021 08:47:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <20210414080845.11426-1-lijunp213@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/14/21 10:08 AM, Lijun Pan wrote: > There are chances that napi_disable can be called twice by NIC driver. > This could generate deadlock. For example, > the first napi_disable will spin until NAPI_STATE_SCHED is cleared > by napi_complete_done, then set it again. > When napi_disable is called the second time, it will loop infinitely > because no dev->poll will be running to clear NAPI_STATE_SCHED. > > Though it is driver writer's responsibility to make sure it being > called only once, making napi_disable more robust does not hurt, not > to say it can prevent a buggy driver from crashing a system. This is hard to digest. A buggy driver has plenty of ways to crash the system. If you need help to fix the buggy driver, please ask for help.