netdev - Re: [PATCH net-next 08/10] bpf: nfp: Report bpf_prog ID during XDP_QUERY

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Message-ID: <20170613045411.2jxep4iotlsilfdt@dhcp-172-26-110-210.dhcp.thefacebook.com>
Date:   Mon, 12 Jun 2017 21:54:17 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: Re: [PATCH net-next 08/10] bpf: nfp: Report bpf_prog ID during
 XDP_QUERY_PROG

On Mon, Jun 12, 2017 at 06:28:42PM -0700, Jakub Kicinski wrote:
> On Mon, 12 Jun 2017 18:00:23 -0700, Martin KaFai Lau wrote:
> > +	case XDP_QUERY_PROG: {
> > +		const struct bpf_prog *xdp_prog;
> > +
> > +		xdp_prog = READ_ONCE(nn->dp.xdp_prog);
> > +		if (xdp_prog)
> > +			xdp->prog_id = xdp_prog->aux->id;
> > +		else
> > +			xdp->prog_id = 0;
> >  		return 0;
> > +	}
> >  	default:
> >  		return -EINVAL;
> >  	}
>
> Why READ_ONCE?  I thought .ndo_xdp is always called under RTNL.
will remove in the next spin.