From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cong Wang <xiyou.wangcong@gmail.com>
Subject: Re: [patch net-next] net: sched: don't dump chains only held by actions
Date: Mon, 30 Jul 2018 11:19:56 -0700
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 <CAM_iQpV2LXPD-8PD=gK_xsuSv7nvQKZbg-miQdUDaQCcx3XjNw@mail.gmail.com> <20180729075146.GA2260@nanopsycho.orion>
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Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
        David Miller <davem@davemloft.net>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Jakub Kicinski <jakub.kicinski@netronome.com>,
        mlxsw@mellanox.com
To: Jiri Pirko <jiri@resnulli.us>
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On Sun, Jul 29, 2018 at 12:54 AM Jiri Pirko <jiri@resnulli.us> wrote:
>
> Sat, Jul 28, 2018 at 07:39:36PM CEST, xiyou.wangcong@gmail.com wrote:
> >On Sat, Jul 28, 2018 at 10:20 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> >>
> >> On Fri, Jul 27, 2018 at 12:47 AM Jiri Pirko <jiri@resnulli.us> wrote:
> >> >
> >> > From: Jiri Pirko <jiri@mellanox.com>
> >> >
> >> > In case a chain is empty and not explicitly created by a user,
> >> > such chain should not exist. The only exception is if there is
> >> > an action "goto chain" pointing to it. In that case, don't show the
> >> > chain in the dump. Track the chain references held by actions and
> >> > use them to find out if a chain should or should not be shown
> >> > in chain dump.
> >> >
> >> > Signed-off-by: Jiri Pirko <jiri@mellanox.com>
> >>
> >> Looks reasonable to me.
> >>
> >> Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
> >
> >Hold on...
> >
> >If you increase the refcnt for a zombie chain on NEWCHAIN path,
> >then it would become a non-zombie, this makes sense. However,
> >if the action_refcnt gets increased again when another action uses it,
> >it become a zombie again because refcnt==action_refcnt??
>
> No. action always increases both refcnt and action_refcnt

Hmm, then the name zombie is confusing, with your definition all
chains implicitly created by actions are zombies, unless touched
by user explicitly. Please find a better name.

Also, tcf_chain_get_by_act() could send out RTM_NEWCHAIN too,
which is confusing too as it is still a "zombie".