[MPTCP] Re: [PATCH v1 2/4] imptcp: cleanup fallback handling

[Florian Westphal <fw at strlen.de>]

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Paolo Abeni <pabeni(a)redhat.com> wrote:
> On Mon, 2019-12-09 at 18:28 -0800, Mat Martineau wrote:
> > I did just say "locking looks ok", but just below this is some iteration 
> > over msk->conn_list without the msk lock held. The locking there is 
> > unaffected by your patch, but this might be a good chance to take a look 
> > at the locking around that list iteration!
> 
> Thank you for the feedback! I'll cope in the next iteration.
> 
> The lockless access to msk->conn_list requires a bit more changes, I'm
> unsure I can deal with that in a timely manner. I'll try. 
>
> Idea would be  dropping the intermendiate inet_accept() call and open-
> code part of it, so we don't have to acquire and release the locks
> multiple times.

What about delaying

inet_sk_state_store(newsk, TCP_ESTABLISHED);

until after this unlocked list iteration?

This would/should prevent any concurrent joins and thus any
list modifications.