Subject: Re: [PATCH net-next v4 07/17] net: sched: protect filter_chain list with filter_chain_lock mutex

From: Vlad Buslov <[email-masked]>
Date: Tue, 19 Feb 2019 12:31:56 +0000

On Tue 19 Feb 2019 at 05:26, Cong Wang <[email-masked]> wrote:
> On Fri, Feb 15, 2019 at 7:35 AM Vlad Buslov <[email-masked]> wrote:
>>
>> Another problem that I found in cls_fw and cls_route is that they set
>> arg->stop when empty. Both of them have code unchanged since it was
>> committed initially in 2005 so I assume this convention is no longer
>> relevant because all other classifiers don't do that (they only set
>> arg->stop when arg->fn returns negative value).
>>
>
> The question is why do you want to use arg->stop==0 as
> an indication for emptiness? Isn't what arg->count==0
> supposed to be?

Good question! I initially wanted to implement it like that, but
reconsidered because iterating through all filters on classifier to
count them is O(N), and terminating on first filter and relying on
arg->stop==1 is constant time. Making function that is called
"tcf_proto_is_empty" linear on number of filters seemed sloppy to me...