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=-0.9 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 9ABDFC43219 for ; Sat, 27 Apr 2019 23:56:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56E7A20823 for ; Sat, 27 Apr 2019 23:56:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="l+yb4vYh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726173AbfD0X4Y (ORCPT ); Sat, 27 Apr 2019 19:56:24 -0400 Received: from mail-pg1-f179.google.com ([209.85.215.179]:34240 "EHLO mail-pg1-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726079AbfD0X4X (ORCPT ); Sat, 27 Apr 2019 19:56:23 -0400 Received: by mail-pg1-f179.google.com with SMTP id c13so2364753pgt.1 for ; Sat, 27 Apr 2019 16:56:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:from:subject:message-id:date:user-agent:mime-version :content-language:content-transfer-encoding; bh=QTDO2UnVIhwg1o2JfUHUOmHH9MJV/+697QTnIx10FyM=; b=l+yb4vYhNrdHSFyX/tsfnH4D1/fEo0fKAPOcpBK+6UonUz3X2RyptHCDovkAK9izhx o365vztDPIFU+g1uwT4JISgegcdsk5zyz4H1Z0qnGCMN3ud4TVs/2yUIqokkDy/hJKiZ FpAyjh4Mu3fQrFQ04qxc6XnlaqToebO7Bjs2TAEzWYnXyDPJr/fP8cs/KSR+1L19MYzP Cf76v6Fs6DYNz/CaWbcM2HjqCfvz8HfWYDLzYTV17gBtsoyVIxWUWtrmAumPGzvCx++I O8UhzcDe41qxG98aMGlk72o8rVCp3OcyIWjAf8BrAoP+jARWPoLVRHh0ksBxEC/5MdqR QOUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:from:subject:message-id:date:user-agent :mime-version:content-language:content-transfer-encoding; bh=QTDO2UnVIhwg1o2JfUHUOmHH9MJV/+697QTnIx10FyM=; b=K3My9CvaHEb/5C/cCtfS24SK+VHiyJo2b3daDrgqULqMrFNg5NR5QYHX9T1r3fd9Wh 4a1vDvagPc2K87WOuv3hrMuw3yJ8sWVJ7tcZija2N9pqi6a3/onAtVlfuMDv6NfQvaf4 E3Jid1uaCDVfIDQfoCG4+8W/DvnkG0UjC1QlRrY7T0ce8dd+NyDOBszF6vIlMX0urD7E cXIUkMJUvv8azEiEdFWYadHK5xZfFAAqiNeGvZDA4WElQoGRyFnndwvtHwkQAeJU/6i2 11Wdg1+oQtz+ZG3U6Uo18xvkdiAkStoFBqQmd3u21zZ5LaDnLdBtb5qwQWyDR6mP56dS YvSA== X-Gm-Message-State: APjAAAWm/mF2qCJaRALuLQ7V4VIDBY4G+HnjjYQduzY/4x8ejprBD3iq 5dQh3BvS5sx48kHtFPACLxJPE3Jj X-Google-Smtp-Source: APXvYqwxj5X26fE/1MuYtUErN3yhu/5mqKzQaVsbLuhKenXaZ2WkjUDSXiCt2sQ2lhc+AZ3RujgpzA== X-Received: by 2002:a63:5b58:: with SMTP id l24mr49783910pgm.139.1556409382902; Sat, 27 Apr 2019 16:56:22 -0700 (PDT) Received: from [192.168.86.235] (c-73-241-150-70.hsd1.ca.comcast.net. [73.241.150.70]) by smtp.gmail.com with ESMTPSA id q20sm29759573pfi.166.2019.04.27.16.56.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 27 Apr 2019 16:56:21 -0700 (PDT) To: David Ahern , Networking From: Eric Dumazet Subject: About ip6_dst_destroy() Message-ID: <3e01083c-ba34-e515-bb3d-d85a98f90e61@gmail.com> Date: Sat, 27 Apr 2019 16:56:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 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 David I am staring at ip6_dst_destroy() and the last part makes really no sense to me. How rcu_read_lock()/rcu_read_unnlock() can help in a writer side ??? Changlog of a68886a691804d3f6d479ebf6825480fbafb6a00 ("net/ipv6: Make from in rt6_info rcu protected") does not make sense either. There is a race window when a FIB entry is deleted and the 'from' on the pcpu route is dropped and the pcpu route hits a cookie check. Handle this race using rcu on from.