RE: [PATCH v2 net 3/3] net: enetc: disable IRQ after Rx and Tx BD rings are disabled

[Wei Fang]

> -----Original Message-----
> From: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> Sent: 2024年10月9日 6:48
> To: Wei Fang <wei.fang@xxxxxxx>
> Cc: davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; Claudiu Manoil <claudiu.manoil@xxxxxxx>;
> ast@xxxxxxxxxx; daniel@xxxxxxxxxxxxx; hawk@xxxxxxxxxx;
> john.fastabend@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; bpf@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx;
> imx@xxxxxxxxxxxxxxx; rkannoth@xxxxxxxxxxx; maciej.fijalkowski@xxxxxxxxx;
> sbhatta@xxxxxxxxxxx
> Subject: Re: [PATCH v2 net 3/3] net: enetc: disable IRQ after Rx and Tx BD rings
> are disabled
> 
> On Tue, Oct 08, 2024 at 06:30:49AM +0300, Wei Fang wrote:
> > I think the reason is that Rx BDRs are disabled when enetc_stop() is called,
> > but there are still many unprocessed frames on Rx BDR. These frames will
> > be processed by XDP program and put into Tx BDR. So enetc_wait_txbdr()
> > will timeout and cause xdp_tx_in_flight will not be cleared.
> >
> > So based on this patch, we should add a separate patch, similar to the patch
> > 2 ("net: enetc: fix the issues of XDP_REDIRECT feature "), which prevents the
> > XDP_TX frames from being put into Tx BDRs when the ENETC_TX_DOWN flag
> > is set. The new patch is shown below. After adding this new patch, I followed
> > your test steps and tested for more than 30 minutes, and the issue cannot be
> > reproduced anymore (without this patch, this problem would be reproduced
> > within seconds).
> >
> > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > @@ -1606,6 +1606,12 @@ static int enetc_clean_rx_ring_xdp(struct
> enetc_bdr *rx_ring,
> >                         break;
> >                 case XDP_TX:
> >                         tx_ring = priv->xdp_tx_ring[rx_ring->index];
> > +                       if (unlikely(test_bit(ENETC_TX_DOWN,
> &priv->flags))) {
> > +                               enetc_xdp_drop(rx_ring, orig_i, i);
> > +                               tx_ring->stats.xdp_tx_drops++;
> > +                               break;
> > +                       }
> > +
> >                         xdp_tx_bd_cnt =
> enetc_rx_swbd_to_xdp_tx_swbd(xdp_tx_arr,
> >
> rx_ring,
> >
> orig_i, i);
> 
> Yeah, it works on my side as well. Thanks for following up.
> 
> I would argue that the above snippet should be a fixup for the
> "net: enetc: fix the issues of XDP_REDIRECT feature" change, and a
> rewrite of the commit message is in order. Currently, as a reader, I get
> the impression that only XDP_REDIRECT needs to check the ENETC_TX_DOWN
> flag, only for the next patch to come and say "remember what was said
> about the TX ring not being allowed to actively transmit frames while
> disabling it? well, that patch wasn't sufficient to ensure this condition,
> because XDP_TX needs to respect that flag as well!"

Okay, I will merge this snippet into "net: enetc: fix the issues of XDP_REDIRECT
feature" and refine the commit message.