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From:   Guoqing Jiang <guoqing.jiang@linux.dev>
Subject: Re: [PATCH V2] RDMA/rtrs: Call {get,put}_cpu_ptr to silence a debug
 kernel warning
To:     Jinpu Wang <jinpu.wang@ionos.com>,
        Christoph Lameter <cl@gentwo.org>
Cc:     haris.iqbal@ionos.com, jgg@ziepe.ca, linux-rdma@vger.kernel.org
References: <20211128133501.38710-1-guoqing.jiang@linux.dev>
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 <CAMGffEmE6789WiYbX4+XXt3ZwPCcx8AjLDDnhYJsSfb0Pu7oYg@mail.gmail.com>
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Date:   Wed, 1 Dec 2021 16:51:49 +0800
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On 11/30/21 7:03 PM, Jinpu Wang wrote:
> On Tue, Nov 30, 2021 at 11:40 AM Christoph Lameter<cl@gentwo.org>  wrote:
>> On Sun, 28 Nov 2021, Guoqing Jiang wrote:
>>
>>>        int cpu;
>>>
>>>        cpu = raw_smp_processor_id();
>>> -     s = this_cpu_ptr(stats->pcpu_stats);
>>> +     s = get_cpu_ptr(stats->pcpu_stats);
>>>        if (con->cpu != cpu) {
>>>                s->cpu_migr.to++;
>>>
>>> @@ -27,14 +27,16 @@ void rtrs_clt_update_wc_stats(struct rtrs_clt_con *con)
>>>                s = per_cpu_ptr(stats->pcpu_stats, con->cpu);
>>>                atomic_inc(&s->cpu_migr.from);
>>>        }
>>> +     put_cpu_ptr(stats->pcpu_stats);
>>>   }
>>>
>>>   void rtrs_clt_inc_failover_cnt(struct rtrs_clt_stats *stats)
>>>   {
>>>        struct rtrs_clt_stats_pcpu *s;
>>>
>>> -     s = this_cpu_ptr(stats->pcpu_stats);
>>> +     s = get_cpu_ptr(stats->pcpu_stats);
>>>        s->rdma.failover_cnt++;
>>> +     put_cpu_ptr(stats->pcpu_stats);
>> This is equivalent to
>>
>> this_cpu_inc(stats->pcpu_stats.rdma.failover_cnt);
>>
>> Which will also reduce the segment to a single cpu instruction.
> Thanks for your suggestion, Christoph.

Good suggestion!

> As the patch is already applied, I will send a new patch as suggested.

Thanks for it.

Cheers,
Guoqing