From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] net: dev: fix the incorrect hold of net namespace's lo device Date: Wed, 22 Aug 2012 10:39:46 +0200 Message-ID: <1345624786.5158.759.camel@edumazet-glaptop> References: <1345624262-6554-1-git-send-email-gaofeng@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: ebiederm@xmission.com, davem@davemloft.net, netdev@vger.kernel.org To: Gao feng Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:40941 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751354Ab2HVIj4 (ORCPT ); Wed, 22 Aug 2012 04:39:56 -0400 Received: by bkwj10 with SMTP id j10so196733bkw.19 for ; Wed, 22 Aug 2012 01:39:55 -0700 (PDT) In-Reply-To: <1345624262-6554-1-git-send-email-gaofeng@cn.fujitsu.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2012-08-22 at 16:31 +0800, Gao feng wrote: > 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) { Did you miss http://patchwork.ozlabs.org/patch/176517/ or is this patch an alternative ? rcu_barrier() at this place will kill some workloads.