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

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Message-ID:
 <PAXPR04MB85101E82059358F959C0502B887F2@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Wed, 9 Oct 2024 01:31:44 +0000
From: Wei Fang <wei.fang@....com>
To: Vladimir Oltean <vladimir.oltean@....com>
CC: "davem@...emloft.net" <davem@...emloft.net>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>, Claudiu Manoil
	<claudiu.manoil@....com>, "ast@...nel.org" <ast@...nel.org>,
	"daniel@...earbox.net" <daniel@...earbox.net>, "hawk@...nel.org"
	<hawk@...nel.org>, "john.fastabend@...il.com" <john.fastabend@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "bpf@...r.kernel.org"
	<bpf@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "rkannoth@...vell.com"
	<rkannoth@...vell.com>, "maciej.fijalkowski@...el.com"
	<maciej.fijalkowski@...el.com>, "sbhatta@...vell.com" <sbhatta@...vell.com>
Subject: RE: [PATCH v2 net 3/3] net: enetc: disable IRQ after Rx and Tx BD
 rings are disabled

> -----Original Message-----
> From: Vladimir Oltean <vladimir.oltean@....com>
> Sent: 2024年10月9日 6:48
> To: Wei Fang <wei.fang@....com>
> Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> pabeni@...hat.com; Claudiu Manoil <claudiu.manoil@....com>;
> ast@...nel.org; daniel@...earbox.net; hawk@...nel.org;
> john.fastabend@...il.com; linux-kernel@...r.kernel.org;
> netdev@...r.kernel.org; bpf@...r.kernel.org; stable@...r.kernel.org;
> imx@...ts.linux.dev; rkannoth@...vell.com; maciej.fijalkowski@...el.com;
> sbhatta@...vell.com
> 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.