netdev - Re: [PATCH net 2/2] net: bridge: switchdev: Skip MDB replays of pending events

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Message-ID: <20240131150642.mxcssv7l5qfiejkl@skbuf>
Date: Wed, 31 Jan 2024 17:06:42 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Tobias Waldekranz <tobias@...dekranz.com>
Cc: davem@...emloft.net, kuba@...nel.org, roopa@...dia.com,
	razor@...ckwall.org, bridge@...ts.linux.dev, netdev@...r.kernel.org,
	jiri@...nulli.us, ivecera@...hat.com
Subject: Re: [PATCH net 2/2] net: bridge: switchdev: Skip MDB replays of
 pending events

On Wed, Jan 31, 2024 at 01:35:44PM +0100, Tobias Waldekranz wrote:
>  	list_for_each_entry(obj, &mdb_list, list) {
>  		err = br_switchdev_mdb_replay_one(nb, dev,
> -- 
> 2.34.1
> 

I think there's one more race to deal with.

If the switchdev driver has signaled SWITCHDEV_BRPORT_UNOFFLOADED,
it may be that there are still deferred port object deletions.
If the switchdev port is under a LAG which is under the bridge AND is
leaving the LAG, those deferred deletions might run too late, aka after
it will no longer process the deletions, since it has left the bridge
constellation.

To fix that, we need another switchdev_deferred_process() call, after
the br_switchdev_mdb_replay_one() calls, while still under rtnl_lock().
The existing switchdev_deferred_process() call from del_nbp() will not
help, since the net_bridge_port (the LAG) does _not_ disappear.