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From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Eric Dumazet <eric.dumazet@gmail.com>, Dmitry Vyukov <dvyukov@google.com>
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        "David S. Miller" <davem@davemloft.net>,
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        Patrick McHardy <kaber@trash.net>, netdev <netdev@vger.kernel.org>,
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Subject: Re: [PATCH net] ipv6: add complete rcu protection around np->opt
Date: Tue, 01 Dec 2015 12:11:26 +0100
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Hi Eric,

On Mon, Nov 30, 2015, at 04:37, Eric Dumazet wrote:
> -                       opt = xchg(&np->opt, NULL);
> -                       if (opt)
> -                               sock_kfree_s(sk, opt, opt->tot_len);
> +                       opt = xchg((__force struct ipv6_txoptions
> **)&np->opt,
> +                                  NULL);
> +                       if (opt) {
> +                               atomic_sub(opt->tot_len,
> &sk->sk_omem_alloc);
> +                               txopt_put(opt);
> +                       }
>  			pktopt = xchg(&np->pktoptions, NULL);
>  			kfree_skb(pktopt);

Is here something special going on (because of the xchg). I don't see
why you cannot simply use a RCU_INIT_POINTER?

Thanks,
Hannes