netdev - Re: [PATCH bpf-next v3 01/10] net: introduce preferred busy-polling

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Date:   Mon, 23 Nov 2020 16:11:03 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Björn Töpel 
        <bjorn.topel@...el.com>, magnus.karlsson@...el.com, ast@...nel.org,
        daniel@...earbox.net, maciej.fijalkowski@...el.com,
        sridhar.samudrala@...el.com, jesse.brandeburg@...el.com,
        qi.z.zhang@...el.com, edumazet@...gle.com,
        jonathan.lemon@...il.com, maximmi@...dia.com
Subject: Re: [PATCH bpf-next v3 01/10] net: introduce preferred busy-polling

On Thu, 19 Nov 2020 09:30:15 +0100 Björn Töpel wrote:
> @@ -105,7 +105,8 @@ static inline void sk_busy_loop(struct sock *sk, int nonblock)
>  	unsigned int napi_id = READ_ONCE(sk->sk_napi_id);
>  
>  	if (napi_id >= MIN_NAPI_ID)
> -		napi_busy_loop(napi_id, nonblock ? NULL : sk_busy_loop_end, sk);
> +		napi_busy_loop(napi_id, nonblock ? NULL : sk_busy_loop_end, sk,
> +			       READ_ONCE(sk->sk_prefer_busy_poll));

Perhaps a noob question, but aren't all accesses to the new sk members
under the socket lock? Do we really need the READ_ONCE() / WRITE_ONCE()?