From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next v2] net: dev: fix the incorrect hold of net namespace's lo device Date: Thu, 30 Aug 2012 12:22:13 -0400 (EDT) Message-ID: <20120830.122213.445208638524849907.davem@davemloft.net> References: <1345772215-30379-1-git-send-email-gaofeng@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, ebiederm@xmission.com To: gaofeng@cn.fujitsu.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:37406 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752618Ab2H3QWQ (ORCPT ); Thu, 30 Aug 2012 12:22:16 -0400 In-Reply-To: <1345772215-30379-1-git-send-email-gaofeng@cn.fujitsu.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Gao feng Date: Fri, 24 Aug 2012 09:36:55 +0800 > When moving a net device from one net namespace to another > net namespace,dev_change_net_namespace calls NETDEV_DOWN > event,so the original net namespace's dst entries which > beloned to this net device will be put into dst_garbage > list. > > then dev_change_net_namespace will set this net device's > net to the new net namespace. > > If we unregister this net device's driver, this will trigger > the NETDEV_UNREGISTER_FINAL event, dst_ifdown will be called, > and get this net device's dst entries from dst_garbage list, > put these entries' dev to the new net namespace's lo device. > > It's not what we want,actually we need these dst entries hold > the original net namespace's lo device,this incorrect device > holding will trigger emg message like below. > unregister_netdevice: waiting for lo to become free. Usage count = 1 > > so we should call NETDEV_UNREGISTER_FINAL event in > dev_change_net_namespace too,in order to make sure dst entries > already in the dst_garbage list, we need rcu_barrier before we > call NETDEV_UNREGISTER_FINAL event. > > With help form Eric Dumazet. > > Signed-off-by: Gao feng Applied, thanks.