The openvswitch teardown code will immediately call
ovs_netdev_detach_dev() in response to a NETDEV_UNREGISTER notification.
It will then start the dp_notify_work workqueue, which will later end up
calling the vport destroy() callback. This callback takes the RTNL to do
another ovs_netdev_detach_port(), which in this case is unnecessary.
This causes extra pressure on the RTNL, in some cases leading to
"unregister_netdevice: waiting for XX to become free" warnings on
teardown.
We can straight-forwardly avoid the extra RTNL lock acquisition by
checking the device flags before taking the lock, and skip the locking
altogether if the IFF_OVS_DATAPATH flag has already been unset.
Fixes: b07c26511e94 ("openvswitch: fix vport-netdev unregister")
Tested-by: Adrian Moreno <[email protected]>
Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
---
v2:
- Expand comments explaining the logic
net/openvswitch/vport-netdev.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/net/openvswitch/vport-netdev.c b/net/openvswitch/vport-netdev.c
index 91a11067e458..6574f9bcdc02 100644
--- a/net/openvswitch/vport-netdev.c
+++ b/net/openvswitch/vport-netdev.c
@@ -160,10 +160,19 @@ void ovs_netdev_detach_dev(struct vport *vport)
static void netdev_destroy(struct vport *vport)
{
- rtnl_lock();
- if (netif_is_ovs_port(vport->dev))
- ovs_netdev_detach_dev(vport);
- rtnl_unlock();
+ /* When called from ovs_db_notify_wq() after a dp_device_event(), the
+ * port has already been detached, so we can avoid taking the RTNL by
+ * checking this first.
+ */
+ if (netif_is_ovs_port(vport->dev)) {
+ rtnl_lock();
+ /* Check again while holding the lock to ensure we don't race
+ * with the netdev notifier and detach twice.
+ */
+ if (netif_is_ovs_port(vport->dev))
+ ovs_netdev_detach_dev(vport);
+ rtnl_unlock();
+ }
call_rcu(&vport->rcu, vport_netdev_free);
}
--
2.52.0
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