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net: openvswitch: Avoid needlessly taking the RTNL on vport destroy

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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 <amorenoz@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20251211115006.228876-1-toke@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Toke Høiland-Jørgensen 2025-12-11 12:50:05 +01:00 committed by Paolo Abeni
parent 1e5a541420
commit 5498227676
1 changed files with 13 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
net/openvswitch/vport-netdev.c
View File

@ -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);
}