netdev - Re: [net-next PATCH 2/2] net: sched: cls_u32 changes to knode must appear atomic to readers

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Message-ID: <CAHA+R7NWzv8+2aUM1uQX8uZkQv-Dp9fYb0SNwmZqk3gKvXVWtw@mail.gmail.com>
Date:	Wed, 17 Sep 2014 14:11:22 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [net-next PATCH 2/2] net: sched: cls_u32 changes to knode must
 appear atomic to readers

On Wed, Sep 17, 2014 at 12:12 PM, John Fastabend
<john.fastabend@...il.com> wrote:
>
> -static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n)
> +static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n, bool pf)
>  {
>         tcf_unbind_filter(tp, &n->res);
>         tcf_exts_destroy(tp, &n->exts);
>         if (n->ht_down)
>                 n->ht_down->refcnt--;
>  #ifdef CONFIG_CLS_U32_PERF
> -       free_percpu(n->pf);
> +       if (pf)

Nit: 'free_pf' is a better name than just 'pf'.

> +               free_percpu(n->pf);
>  #endif
>  #ifdef CONFIG_CLS_U32_MARK
> -       free_percpu(n->pcpu_success);
> +       if (pf)
> +               free_percpu(n->pcpu_success);
>  #endif
>         kfree(n);
>         return 0;
>  }
>
> +static void u32_delete_key_rcu_pf(struct rcu_head *rcu)
> +{
> +       struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
> +
> +       u32_destroy_key(key->tp, key, false);
> +}

I think you need a comment here to explain why you free it partially
on purpose, it is not that clear, at least I spent some time to figure
it out when I read your cls_tcindex patch.

Thanks!
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