netdev - Re: [Patch net-next] net_sched: add performance counters for basic filter

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Date:   Sun, 3 Feb 2019 19:27:07 -0800
From:   Eric Dumazet <eric.dumazet@...il.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>
Subject: Re: [Patch net-next] net_sched: add performance counters for basic
 filter



On 02/03/2019 11:35 AM, Cong Wang wrote:
> On Sun, Feb 3, 2019 at 10:35 AM Eric Dumazet <eric.dumazet@...il.com> wrote:
>>> +     for_each_possible_cpu(cpu) {
>>> +             struct tc_basic_pcnt *pf = per_cpu_ptr(f->pf, cpu);
>>> +
>>> +             gpf.rcnt += pf->rcnt;
>>> +             gpf.rhit += pf->rhit;
>>> +     }
>>>
>> This looks missing some synchronization of some sort for 32bit kernels ?
> 
> I don't know, u32 filter has literally same code:
> 
>                 for_each_possible_cpu(cpu) {
>                         int i;
>                         struct tc_u32_pcnt *pf = per_cpu_ptr(n->pf, cpu);
> 
>                         gpf->rcnt += pf->rcnt;
>                         gpf->rhit += pf->rhit;
>                         for (i = 0; i < n->sel.nkeys; i++)
>                                 gpf->kcnts[i] += pf->kcnts[i];
>                 }
> 
> which has been there for years...
> 

Then u32 (or at least CONFIG_CLS_U32_PERF) was also broken.