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Date: Sat, 22 Apr 2017 20:52:25 -0700 From: Jakub Kicinski <kubakici@...pl> To: John Fastabend <john.fastabend@...il.com> Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>, davem@...emloft.net, netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com, John Fastabend <john.r.fastabend@...el.com> Subject: Re: [net-next 03/11] ixgbe: add support for XDP_TX action On Sat, 22 Apr 2017 20:40:22 -0700, John Fastabend wrote: > >> @@ -9557,7 +9739,21 @@ static int ixgbe_xdp_setup(struct net_device *dev, struct bpf_prog *prog) > >> return -EINVAL; > >> } > >> > >> + if (nr_cpu_ids > MAX_XDP_QUEUES) > >> + return -ENOMEM; > >> + > >> old_prog = xchg(&adapter->xdp_prog, prog); > >> + > >> + /* If transitioning XDP modes reconfigure rings */ > >> + if (!!prog != !!old_prog) { > >> + int err = ixgbe_setup_tc(dev, netdev_get_num_tc(dev)); > >> + > >> + if (err) { > >> + rcu_assign_pointer(adapter->xdp_prog, old_prog); > >> + return -EINVAL; > >> + } > >> + } > >> + > >> for (i = 0; i < adapter->num_rx_queues; i++) > >> xchg(&adapter->rx_ring[i]->xdp_prog, adapter->xdp_prog); > >> > > > > In case of disabling XDP I assume ixgbe_setup_tc() will free the rings > > before the xdp_prog on the rings is swapped to NULL. Is there anything > > preventing TX in that time window? I think usual ordering would be to > > install the prog after reconfig but uninstall before. > > > > Well in the ixgbe_setup_tc() case we set the rx_ring->xdp_prog in > ixgbe_setup_rx_resorources(), while the dma engine is disabled, so the for > loop is just doing another set on the rx_ring assigning it to the program > already set previously. > > Its not really buggy its just extra useless work so I'll change it to this, > > if (!!prog != !!old_prog) { > ... > } else { > for ( ... ) > swap xdp prog > } > > Nice spot, thanks for reviewing. And I missed a build error so I'll roll these > fixes in a resend. Ah, thanks for explaining. No bugs that I can spot then :)
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