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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 A0BE1C43219 for ; Sun, 28 Apr 2019 04:26:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63B972075D for ; Sun, 28 Apr 2019 04:26:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726415AbfD1EXT (ORCPT ); Sun, 28 Apr 2019 00:23:19 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:61434 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726056AbfD1EXT (ORCPT ); Sun, 28 Apr 2019 00:23:19 -0400 Received: from fsav105.sakura.ne.jp (fsav105.sakura.ne.jp [27.133.134.232]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x3S4MndF079584; Sun, 28 Apr 2019 13:22:49 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav105.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav105.sakura.ne.jp); Sun, 28 Apr 2019 13:22:49 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav105.sakura.ne.jp) Received: from [192.168.1.8] (softbank126012062002.bbtec.net [126.12.62.2]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x3S4MnQB079578 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Sun, 28 Apr 2019 13:22:49 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: unregister_netdevice: waiting for DEV to become free (2) To: Eric Dumazet , David Ahern , "David S. Miller" Cc: Julian Anastasov , Cong Wang , syzbot , ddstreet@ieee.org, dvyukov@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <0000000000007d22100573d66078@google.com> <4684eef5-ea50-2965-86a0-492b8b1e4f52@I-love.SAKURA.ne.jp> <9d430543-33c3-0d9b-dc77-3a179a8e3919@I-love.SAKURA.ne.jp> <920ebaf1-ee87-0dbb-6805-660c1cbce3d0@I-love.SAKURA.ne.jp> <15b353e9-49a2-f08b-dc45-2e9bad3abfe2@i-love.sakura.ne.jp> <057735f0-4475-7a7b-815f-034b1095fa6c@gmail.com> From: Tetsuo Handa Message-ID: <6e57bc11-1603-0898-dfd4-0f091901b422@i-love.sakura.ne.jp> Date: Sun, 28 Apr 2019 13:22:49 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <057735f0-4475-7a7b-815f-034b1095fa6c@gmail.com> 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 2019/04/28 8:52, Eric Dumazet wrote: > On 4/27/19 3:33 PM, Tetsuo Handa wrote: >> >> I'm waiting for davem why it is safe to move the dst entry from >> "a device to unregister" to "a loopback device in that namespace". >> I'm waiting for an explanation how the dst entry which was moved to >> "a loopback device in that namespace" is released (i.e. what the >> expected shutdown sequence is). > > The most probable explanation is that we make sure the loopback device > is the last one to be dismantled at netns deletion, > and this would obviously happen after all dst have been released. > rt_flush_dev() becomes a no-op if "dev" == "a loopback device in that namespace". And according to debug printk(), rt_flush_dev() is called on "a loopback device in that namespace" itself. If "a loopback device in that namespace" is the last "one" (== "a network device in that namespace" ?), which shutdown sequence should have called dev_put("a loopback device in that namespace") before unregistration of "a loopback device in that namespace" starts? Since I'm not a netdev person, I appreciate if you can explain that shutdown sequence using a flow chart.