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

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Date:   Tue, 19 Feb 2019 10:25:40 +0000
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>,
        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 18 Feb 2019 at 19:55, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Mon, Feb 18, 2019 at 3:19 AM Vlad Buslov <vladbu@...lanox.com> wrote:
>>
>>
>> On Fri 15 Feb 2019 at 23:17, Cong Wang <xiyou.wangcong@...il.com> wrote:
>> > 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?
>>
>> This lock is intended to be used by unlocked classifiers and I use it in
>> my following flower patch set extensively. Classifiers that do not set
>> 'unlocked' flag continue to rely on rtnl lock for synchronization.
>
> It is never late to add it when you seriously use it. The way you
> split the patches is really annoying for reviewers...

I made a decision to put all required cls API changes so at this point
anyone can implement their own rtnl-unlocked classifier (or refactor
existing one for unlocked execution) without any further changes to cls
API. However, I can see how this can be confusing to reviewer,
especially if they are not familiar with proposed flower changes. I will
split my patches according to your suggestions in the future.

Thanks,
Vlad