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Date:   Mon, 23 Nov 2020 16:11:03 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
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        <bjorn.topel@intel.com>, magnus.karlsson@intel.com, ast@kernel.org,
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        qi.z.zhang@intel.com, edumazet@google.com,
        jonathan.lemon@gmail.com, maximmi@nvidia.com
Subject: Re: [PATCH bpf-next v3 01/10] net: introduce preferred busy-polling
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On Thu, 19 Nov 2020 09:30:15 +0100 Bj=C3=B6rn T=C3=B6pel wrote:
> @@ -105,7 +105,8 @@ static inline void sk_busy_loop(struct sock *sk, int =
nonblock)
>  	unsigned int napi_id =3D READ_ONCE(sk->sk_napi_id);
> =20
>  	if (napi_id >=3D 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()?