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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 87244C169C4 for ; Thu, 7 Feb 2019 00:28:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 564BD2084D for ; Thu, 7 Feb 2019 00:28:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TUkoiROb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726733AbfBGA2g (ORCPT ); Wed, 6 Feb 2019 19:28:36 -0500 Received: from mail-pg1-f194.google.com ([209.85.215.194]:41881 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726424AbfBGA2f (ORCPT ); Wed, 6 Feb 2019 19:28:35 -0500 Received: by mail-pg1-f194.google.com with SMTP id m1so3701262pgq.8 for ; Wed, 06 Feb 2019 16:28:35 -0800 (PST) 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=qnwC0ueoi6x7oW6xhMY5uKe2tRAWduW6cZ/vIO6AwwU=; b=TUkoiRObdCIGRRjZIVA5GojlwF4zTTAxV4KYpS9CdTLgmD2s9fEzvdDAjFtUY9ieAR yxL4X87j2aeJIw/GuukNiEpbFYLlrdzcoN0ix389kAxF/GV5QWd1sbDfV8tWO+jodA1a P9fqcLi3e+3aXLLW3NUYwTICc5TfRc3nt76WgwqPGytABatt8OzPNsCmC8L7bbgdx1jF WjiL1StJ0RBidia7Usep9fiIUNXY4wJDGpDVT6g6E4SCJogoJCnr+zMgL+5jMAcRp/op Yu/JxiLjhShQwc2+ZIbLxtbmb2RvGgq33hTVhcQg6tLYiMI1oQnCTXfvW1STU27mR8Ym A94Q== 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=qnwC0ueoi6x7oW6xhMY5uKe2tRAWduW6cZ/vIO6AwwU=; b=r/9ZjaO1KYdL02HO17+RX+TyFFxIe9/80NKQrp1zHXNp1f57jb76GauKrS/1DrL8FZ XfqGYcAIOGvK5ecz2S4Os3yAJ+4zSOEVVKLAdBa3ES4T0MxaR6Y8NrpEN6CZ+3JlhNYU +XsEIlUtsvhDJobT99mgDzwXq/O5adVJQPRu2TI3S0XyIw6yVmhtVH4oxReazB9UM30v UOUHhyXpBX82ez4NCIQlVZD8bXWaAczOsnkCn9/kXQPGblarbs/c8UpLO186jXPIb/Co b7rtjLJDjVq0M1a+iM0iEqf/uIltBovNQXN+IzYPqoq5h9ZiSQEcatmEvwESPFP/Bcki 0JeQ== X-Gm-Message-State: AHQUAubBYwNpJfA5qQIEH3WiYmCC1VzR6nE2EyJbiWgsUU+2KbauYQKI h3194GMPgs0/aLaN8HPMt9A= X-Google-Smtp-Source: AHgI3IYygWiA6MiZH6ZVh56+LmMS+W55NB5yURstqn09dh3UNEZqgvjoFI5+BjF0GkklB4vSLikFsQ== X-Received: by 2002:a65:5bc4:: with SMTP id o4mr12337427pgr.426.1549499314926; Wed, 06 Feb 2019 16:28:34 -0800 (PST) Received: from [192.168.88.84] (ip-24-221-53-235.brbnca.spcsdns.net. [24.221.53.235]) by smtp.gmail.com with ESMTPSA id n73sm10479707pfj.148.2019.02.06.16.28.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Feb 2019 16:28:33 -0800 (PST) Subject: Re: [Patch net-next v2] mlx5: use RCU lock in mlx5_eq_cq_get() To: Cong Wang , Eric Dumazet Cc: Linux Kernel Network Developers , Saeed Mahameed , Tariq Toukan References: <20190206230019.1303-1-xiyou.wangcong@gmail.com> <52ed9806-310d-bfeb-9610-0daefc1e66fa@gmail.com> From: Eric Dumazet Message-ID: Date: Wed, 6 Feb 2019 16:28:25 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 02/06/2019 04:04 PM, Cong Wang wrote: > synchronize_irq() is called before mlx5_cq_put(), so I don't > see why readers could get 0 refcnt. Then the more reasons to get rid of the refcount increment/decrement completely ... Technically, even the rcu_read_lock() and rcu_read_unlock() are not needed, since synchronize_irq() is enough. > > For the rds you mentioned, it doesn't wait for readers, this > is why it needs to check against 0 and why it is different from > this one. > > Thanks. >