netdev - Re: [EXT] Re: [PATCH 1/1] net: fec: add initial XDP support

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Message-ID: <YzWcdsGkq4x8VWbY@lunn.ch>
Date:   Thu, 29 Sep 2022 15:24:06 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Shenwei Wang <shenwei.wang@....com>
Cc:     Joakim Zhang <qiangqing.zhang@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: Re: [EXT] Re: [PATCH 1/1] net: fec: add initial XDP support

> > > +struct fec_enet_xdp_stats {
> > > +     u64     xdp_pass;
> > > +     u64     xdp_drop;
> > > +     u64     xdp_xmit;
> > > +     u64     xdp_redirect;
> > > +     u64     xdp_xmit_err;
> > > +     u64     xdp_tx;
> > > +     u64     xdp_tx_err;
> > > +};
> > > +
> > > +     switch (act) {
> > > +     case XDP_PASS:
> > > +             rxq->stats.xdp_pass++;
> > 
> > Since the stats are u64, and most machines using the FEC are 32 bit, you cannot
> > just do an increment. Took a look at u64_stats_sync.h.
> > 
> 

> As this increment is only executed under the NAPI kthread context,
> is the protection still required?

Are the statistics values read by ethtool under NAPI kthread context?

    Andrew