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

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Message-ID: <20170612182842.3150789d@cakuba.netronome.com>
Date:   Mon, 12 Jun 2017 18:28:42 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Martin KaFai Lau <kafai@...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, 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.