netdev - Re: [PATCH v2] net: openvswitch: Avoid needlessly taking the RTNL on vport destroy

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Message-ID: <f7t5xa7anvk.fsf@redhat.com>
Date: Mon, 15 Dec 2025 08:14:07 -0500
From: Aaron Conole <aconole@...hat.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: Eelco Chaudron <echaudro@...hat.com>,  Ilya Maximets
 <i.maximets@....org>,  Alexei Starovoitov <ast@...nel.org>,  Jesse Gross
 <jesse@...ira.com>,  Adrian Moreno <amorenoz@...hat.com>,  "David S.
 Miller" <davem@...emloft.net>,  Eric Dumazet <edumazet@...gle.com>,  Jakub
 Kicinski <kuba@...nel.org>,  Paolo Abeni <pabeni@...hat.com>,  Simon
 Horman <horms@...nel.org>,  netdev@...r.kernel.org,  dev@...nvswitch.org
Subject: Re: [PATCH v2] net: openvswitch: Avoid needlessly taking the RTNL
 on vport destroy

Toke Høiland-Jørgensen <toke@...hat.com> writes:

> 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@...hat.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---

LGTM,

Acked-by: Aaron Conole <aconole@...hat.com>