On 02/09/2020 23:55, David Miller wrote: > From: Edward Cree <ec...@solarflare.com> > Date: Wed, 2 Sep 2020 15:35:53 +0100 > >> + tx_queue->xmit_more_available = true; > > I don't understand why you're setting xmit_more_available > unconditionally to true now instead of setting it to 'xmit_more' as > seen by this transmit attempt. Why would you want to signal > that xmit_more handling might be necessary when you haven't been > given an xmit_more tx request?
After this patch xmit_more_available is something of a misnomer and really means "xmit pending" (I'll rename it in v2). We unconditionally set it to true here so that efx_tx_send_pending() knows there is something to do on this queue; but then we only call efx_tx_send_pending if !xmit_more (per the __netdev_tx_sent_queue() call). Then efx_tx_send_pending, via the efx->type->tx_write methods, sets xmit_more_available to false. Thus xmit_more_available is only true on return from __efx_enqueue_skb() if we had xmit_more (and __netdev_tx_sent_queue didn't say "ring it anyway"). > If this change is in fact correct, it's something you need to explain > in the commit message. Will do so for v2, as it is indeed far from obvious. -ed
