netdev - Re: [PATCH net-next v2 2/2] net/sched: act_csum: don't use spinlock in the fast path

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Message-ID: <CAM_iQpWybQrpEddtdbCgy8u6_b46orzddko2Spy8nxEGtwG4pA@mail.gmail.com>
Date:   Sun, 21 Jan 2018 12:28:12 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH net-next v2 2/2] net/sched: act_csum: don't use spinlock
 in the fast path

On Fri, Jan 19, 2018 at 6:12 AM, Davide Caratti <dcaratti@...hat.com> wrote:
>  static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
> @@ -575,15 +594,18 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
>  {
>         unsigned char *b = skb_tail_pointer(skb);
>         struct tcf_csum *p = to_tcf_csum(a);
> +       struct tcf_csum_params *params;
>         struct tc_csum opt = {
> -               .update_flags = p->update_flags,
>                 .index   = p->tcf_index,
> -               .action  = p->tcf_action,
>                 .refcnt  = p->tcf_refcnt - ref,
>                 .bindcnt = p->tcf_bindcnt - bind,
>         };
>         struct tcf_t t;
>
> +       params = rcu_dereference(p->params);

I think you need rtnl_dereference() here, as we don't have RCU read lock here?


> +       opt.action = params->action;
> +       opt.update_flags = params->update_flags;
> +


Thanks.