From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gao feng Subject: [PATCH] net: dev: fix the incorrect hold of net namespace's lo device Date: Wed, 22 Aug 2012 16:31:02 +0800 Message-ID: <1345624262-6554-1-git-send-email-gaofeng@cn.fujitsu.com> Cc: davem@davemloft.net, eric.dumazet@gmail.com, netdev@vger.kernel.org, Gao feng To: ebiederm@xmission.com Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:6790 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750769Ab2HVIaw (ORCPT ); Wed, 22 Aug 2012 04:30:52 -0400 Sender: netdev-owner@vger.kernel.org List-ID: in dst_dev_event,we get the still referenced dst entries from dst_garbage list,and call dst_ifdown to change these dst entries' device to the net namesapce's lo device. when we moving a net device(A) to another net namespace, because free_fib_info_rcu is called after a grace period, we may call dst_dev_event before free_fib_info_rcu putting dst_entry into the dst_garbage list. so in dst_dev_event, we can't see these dst entries through dst_garbage list, and without changing their device to the old net namespace's lo device. after a grace period, these dst entries which dst->dev is device A will in the dst_garbage list, and the device A will belong to the new net namespcae. then we exit from this new net namespace, the dst_dev_event is called again,it will get these dst entries from dst_garbage list,and call dst_ifdown to hold the new net namespace's lo device incorrectly and put the device A. so it will tigger the emg message in netdev_wait_allrefs like below. unregister_netdevice: waiting for lo to become free. Usage count = 1 fix this problem by adding rcu_barrier() in dst_dev_event when event is NETDEV_UNREGISTER. with this,dst_ifdown will be called after the dst_garbage list beeing updated. Signed-off-by: Gao feng --- net/core/dst.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/net/core/dst.c b/net/core/dst.c index 56d6361..38c2199 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -375,6 +375,7 @@ static int dst_dev_event(struct notifier_block *this, unsigned long event, switch (event) { case NETDEV_UNREGISTER: + rcu_barrier(); case NETDEV_DOWN: mutex_lock(&dst_gc_mutex); for (dst = dst_busy_list; dst; dst = dst->next) { -- 1.7.7.6