From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: [CFT][PATCH] net: Delay default_device_exit_batch until no devices are unregistering Date: Mon, 16 Sep 2013 20:49:31 -0700 Message-ID: <87mwncaz04.fsf_-_@xmission.com> References: <1379008796-2121-1-git-send-email-fruggeri@aristanetworks.com> <87txhp249u.fsf@xmission.com> <871u4t1d9t.fsf@xmission.com> <87d2ocrx9b.fsf@xmission.com> <87six5kpu5.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain Cc: "David S. Miller" , Eric Dumazet , Jiri Pirko , Alexander Duyck , Cong Wang , netdev@vger.kernel.org To: Francesco Ruggeri Return-path: Received: from out01.mta.xmission.com ([166.70.13.231]:43373 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511Ab3IQFK5 (ORCPT ); Tue, 17 Sep 2013 01:10:57 -0400 In-Reply-To: (Francesco Ruggeri's message of "Mon, 16 Sep 2013 13:30:50 -0700") Sender: netdev-owner@vger.kernel.org List-ID: The implementation is a little rough but the logic should be right. Device registration and unregistration is serialized with the rtnl_lock. The final pieces of device unregistration do not happen under the rtnl_lock resulting in the possibility that while we wait for the refcount of a device to drop to zero the network namespace is unregistered while no locks are held. Prevent that by keeping a count of the network devices that are being unregistered and before we make the final pass through a network namespace to flush out all of the network devices, wait for the count of network devices being unregistered to drop to zero. Reported-by: Francesco Ruggeri Signed-off-by: "Eric W. Biederman" --- Francesco could you take a look at this. I am about 99% certain this is right but I am starting to fade. So it is entirely possible I missed something. net/core/dev.c | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 5d702fe..c25e6f3 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5002,10 +5002,13 @@ static int dev_new_index(struct net *net) /* Delayed registration/unregisteration */ static LIST_HEAD(net_todo_list); +static atomic_t netdev_unregistering = ATOMIC_INIT(0); +static DECLARE_WAIT_QUEUE_HEAD(netdev_unregistering_wait); static void net_set_todo(struct net_device *dev) { list_add_tail(&dev->todo_list, &net_todo_list); + atomic_inc(&netdev_unregistering); } static void rollback_registered_many(struct list_head *head) @@ -5673,6 +5676,9 @@ void netdev_run_todo(void) if (dev->destructor) dev->destructor(dev); + if (atomic_dec_and_test(&netdev_unregistering)) + wake_up(&netdev_unregistering_wait); + /* Free network device */ kobject_put(&dev->dev.kobj); } @@ -6369,7 +6375,13 @@ static void __net_exit default_device_exit_batch(struct list_head *net_list) struct net *net; LIST_HEAD(dev_kill_list); +retry: + wait_event(netdev_unregistering_wait, (atomic_read(&netdev_unregistering) == 0)); rtnl_lock(); + if (atomic_read(&netdev_unregistering) != 0) { + __rtnl_unlock(); + goto retry; + } list_for_each_entry(net, net_list, exit_list) { for_each_netdev_reverse(net, dev) { if (dev->rtnl_link_ops) -- 1.7.5.4