Re: [PATCH wireless v2] wifi: wext: Limit notifier event flushes to the device's netns

[Jakub Kicinski <kuba@kernel.org>]

On Fri, 23 Oct 2026 11:10:44 +0300 Cosmin Ratiu wrote:
> With mlx5 netdev instance locking enabled, registering an IPoIB netdev
> calls the WEXT notifier while holding the instance mutex. Its call to
> wireless_nlevent_flush() takes net_rwsem to walk every namespace,
> completing the following lockdep dependency cycle:
> 
>   netdev instance mutex -> net_rwsem (read) -> GID table mutex
>     -> event_handler_rwsem (read) -> netdev instance mutex  
> 
> RoCE GID enumeration takes the GID table mutex under net_rwsem. GID
> updates dispatch events under the table mutex, taking event_handler_rwsem.
> The IPoIB event handler takes the netdev instance mutex in
> ipoib_queue_work() to traverse child interfaces.
> 
> The all-namespace walk originated in the single global worker servicing
> per-namespace WEXT queues. The ordering fixes later reused that routine
> in netdevice notifiers to prevent delayed WEXT RTM_NEWLINK messages from
> following RTM_DELLINK or reporting stale interface flags. A notifier only
> needs to drain the affected device's namespace; there is no reason for it
> to walk and flush all namespaces.
> 
> Pass dev_net(dev) from both notifier callers and make the flush helper
> operate on that namespace. Keep the all-namespace walk and net_rwsem in
> the existing worker. This removes the instance-mutex -> net_rwsem
> dependency while retaining synchronous flushing from the notifiers.
> 
> It may seem strange that the fix for a lock cycle across multiple
> subsystems lies in a completely unrelated part of the code, but this
> seemed the most justified lock cycle edge to break.

If Johannes thinks this scoping is good for other reasons - SGTM.
But my knee jerk fix would be to skip all the wifi processing
for ops-locked devices since no wifi device is ops locked.