Re: [PATCH net-next v19 00/26] Introducing OpenVPN Data Channel Offload

[Sean Anderson <seanga2@gmail.com>]

Hi Antonio,

On 2/10/25 19:39, Antonio Quartulli wrote:
> NOTE: TCP tests are still showing the following warning while running
> iperf.
> I have analysed the report several times, but it definitely looks like
> a false positive to me, so nothing to worry about.
> 
> Basically the lockdep engine gets confused thinking that we are
> acquiring the lock twice on the same sock, but actually:
> 1) the kernel is first locking the 'iperf' (user) TCP socket;
> 2) ovpn is later locking the underlying TCP trasport socket.
> 
> So there is NO risk of deadlock (and indeed nothing hangs), but I
> couldn't find a way to make the warning go away.

I think you can use a "nested" lock to avoid this. See e.g. commit
86a41ea9fd79 ("l2tp: fix lockdep splat") for an example.

--Sean

[1] https://www.kernel.org/doc/html/latest/locking/lockdep-design.html#exception-nested-data-dependencies-leading-to-nested-locking