netdev - Re: [PATCH net-next 2/2] net: sched: do not acquire qdisc spinlock in qdisc/class stats dump

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Date:	Mon, 6 Jun 2016 16:15:42 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <edumazet@...gle.com>
Cc:	"David S . Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	John Fastabend <john.fastabend@...il.com>,
	Kevin Athey <kda@...gle.com>,
	Xiaotian Pei <xiaotian@...gle.com>
Subject: Re: [PATCH net-next 2/2] net: sched: do not acquire qdisc spinlock in
 qdisc/class stats dump

On Mon, Jun 6, 2016 at 9:37 AM, Eric Dumazet <edumazet@...gle.com> wrote:
>  void
> -__gnet_stats_copy_basic(struct gnet_stats_basic_packed *bstats,
> +__gnet_stats_copy_basic(const seqcount_t *running,
> +                       struct gnet_stats_basic_packed *bstats,
>                         struct gnet_stats_basic_cpu __percpu *cpu,
>                         struct gnet_stats_basic_packed *b)
>  {
> +       unsigned int seq;
> +
>         if (cpu) {
>                 __gnet_stats_copy_basic_cpu(bstats, cpu);
> -       } else {
> +               return;
> +       }
> +       do {
> +               if (running)
> +                       seq = read_seqcount_begin(running);
>                 bstats->bytes = b->bytes;
>                 bstats->packets = b->packets;
> -       }
> +       } while (running && read_seqcount_retry(running, seq));
>  }

Why only these basic stats need to get read seqlock?
Queue stats (gnet_stats_copy_queue()) too, right?