Re: [mptcp-next 2/2] mptcp: re-set push-pending bit on retransmit failure

[Paolo Abeni <pabeni@redhat.com>]

On Mon, 2021-09-06 at 09:55 +0200, Florian Westphal wrote:
> Paolo Abeni <pabeni@redhat.com> wrote:
> > > +	/* Set PENDING again in case we found an ssk
> > > +	 * that could not accept more data
> > > +	 */
> > > +	if (unlikely(copied == 0) &&
> > > +	    READ_ONCE(msk->snd_una) == msk->snd_nxt && ssk)
> > > +		mptcp_check_and_set_pending(sk);
> > 
> > @Florian: Why we need to check for ssk != NULL?
> 
> Because I don't think it makes sense to re-try ASAP if we could
> not find a ssk, and instead defer until next firing of rtx timer.

Ok
> 
> > Do we need something similar for __mptcp_subflow_push_pending(), too?
> 
> I don't think so, its thats not invoked from the mptcp-release cb; 

yup, right. To be clear, with "something similar" I also referred to
ensuring the rtx timer is armed.

> also:
> 
> > I'm wondering if this will cause a sort of 'spinning'/busy loop on
> > above condition inside mptcp_release_cb().
> 
> Hmm, right, that might indeed happen.
> It should be sae to remove the above clause and unconditioally wait
> for the reworked rtx timer to assert pending bit again.

+1 :) (assuming s/sae/safe/ :)

Thanks!

Paolo