From mboxrd@z Thu Jan 1 00:00:00 1970 From: Apollon Oikonomopoulos Subject: [PATCH] X.25: decrement netdev reference counts on unload Date: Tue, 7 Dec 2010 21:43:30 +0200 Message-ID: <20101207194330.GA22608@noc.grnet.gr> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-7 To: netdev@vger.kernel.org Return-path: Received: from mail.noc.grnet.gr ([83.212.9.3]:45071 "EHLO mail.noc.grnet.gr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754422Ab0LGTuj (ORCPT ); Tue, 7 Dec 2010 14:50:39 -0500 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hello, We came across this bug when we accidentally loaded and unloaded the x25 kernel module on a host with KVM virtual machines. All subsequent attempts to stop a KVM instance resulted in the KVM process entering D state. Reproducing this behaviour can be done in the following way: 1. modprobe x25 2. tunctl && ifconfig tap0 up 3. rmmod x25 4. tunctl -d tap0 (hangs) A patch follows - we don't use X.25 ourselves so I'm not sure it won't panic someone's system. Regards, Apollon PS: I am not subscribed to the list, so please copy any replies to my address. Thanks! ---- x25 does not decrement the network device reference counts on module unload. Thus unregistering any pre-existing interface after unloading the x25 module hangs and results in unregister_netdevice: waiting for tap0 to become free. Usage count = 1 This patch decrements the reference counts of all interfaces in x25_link_free, the way it is already done in x25_link_device_down for NETDEV_DOWN events. Signed-off-by: Apollon Oikonomopoulos --- net/x25/x25_link.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/net/x25/x25_link.c b/net/x25/x25_link.c index 73e7b95..b25c646 100644 --- a/net/x25/x25_link.c +++ b/net/x25/x25_link.c @@ -394,6 +394,7 @@ void __exit x25_link_free(void) list_for_each_safe(entry, tmp, &x25_neigh_list) { nb = list_entry(entry, struct x25_neigh, node); __x25_remove_neigh(nb); + dev_put(nb->dev); } write_unlock_bh(&x25_neigh_list_lock); } -- 1.7.1