netdev - Re: [PATCH net-next v2 05/10] net: sched: use Qdisc rcu API instead of relying on rtnl lock

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Message-ID: <vbfva70zlb9.fsf@reg-r-vrt-018-180.mtr.labs.mlnx>
Date:   Thu, 20 Sep 2018 10:20:58 +0300
From:   Vlad Buslov <vladbu@...lanox.com>
To:     Cong Wang <xiyou.wangcong@...il.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>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Greg KH <gregkh@...uxfoundation.org>, mark.rutland@....com,
        Leon Romanovsky <leon@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Florian Westphal <fw@...len.de>,
        David Ahern <dsahern@...il.com>, christian@...uner.io,
        lucien xin <lucien.xin@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jiri Benc <jbenc@...hat.com>
Subject: Re: [PATCH net-next v2 05/10] net: sched: use Qdisc rcu API instead of relying on rtnl lock


On Wed 19 Sep 2018 at 22:04, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Mon, Sep 17, 2018 at 12:19 AM Vlad Buslov <vladbu@...lanox.com> wrote:
>> +static void tcf_qdisc_put(struct Qdisc *q, bool rtnl_held)
>> +{
>> +       if (!q)
>> +               return;
>> +
>> +       if (rtnl_held)
>> +               qdisc_put(q);
>> +       else
>> +               qdisc_put_unlocked(q);
>> +}
>
> This is very ugly. You should know whether RTNL is held or
> not when calling it.
>
> What's more, all of your code passes true, so why do you
> need a parameter for rtnl_held?

It passes true because currently rule update handlers still registered
as locked. This is a preparation for next patch set where this would be
changed to proper variable that depends on qdics and classifier type.