netdev - Re: [PATCH net-next v4 10/17] net: sched: refactor tp insert/delete for concurrent execution

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Date:   Fri, 15 Feb 2019 15:17:09 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        David Miller <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH net-next v4 10/17] net: sched: refactor tp insert/delete
 for concurrent execution

On Mon, Feb 11, 2019 at 12:56 AM Vlad Buslov <vladbu@...lanox.com> wrote:
> +static bool tcf_proto_is_empty(struct tcf_proto *tp)
> +{
> +       struct tcf_walker walker = { .fn = walker_noop, };
> +
> +       if (tp->ops->walk) {
> +               tp->ops->walk(tp, &walker);
> +               return !walker.stop;
> +       }
> +       return true;
> +}
> +
> +static bool tcf_proto_check_delete(struct tcf_proto *tp)
> +{
> +       spin_lock(&tp->lock);
> +       if (tcf_proto_is_empty(tp))
> +               tp->deleting = true;
> +       spin_unlock(&tp->lock);
> +       return tp->deleting;

If you use this spinlock for walking each tp data structure,
why it is not needed for adding to/deleting filters from each
tp?