Re: [PATCH v5 2/5] telemetry: fix repeated display when callback don't set dict

[fengchengwen <fengchengwen@huawei.com>]

On 2022/12/19 17:33, Bruce Richardson wrote:
> On Mon, Dec 19, 2022 at 09:07:20AM +0000, Chengwen Feng wrote:
>> When telemetry callback didn't set dict and return a non-negative
>> number, the telemetry will repeat to display the last result.
>>
>> Fixes: 6dd571fd07c3 ("telemetry: introduce new functionality")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
>> ---
> 
> Hi Chengwen,
> 
> I'm a little curious about this bug. Can you describe some steps to
> reproduce it as I'm curious as to exactly what is happening. The fix seems
> a little strange to me so I'd like to investigate a little more to see if
> other approaches might work.

Hi Bruce,

Sorry for late reply.

The steps:
  1. applay "[PATCH v5 1/5] dmadev: support stats reset telemetry command"
  2. compile
  3. start dpdk-dma: dpdk-dma -a DMA.BDF -a NIC.BDF -- -c hw
  4. start telemetry, and execute /dmadev/stats,0, and then /dmadev/stats_reset,0
     the output of /dmadev/stats_reset,0 will be the same of previous cmd "/dmadev/stats,0"
     e.g. my environment:
--> /dmadev/stats,0
{
  "/dmadev/stats": {
    "submitted": 23,
    "completed": 23,
    "errors": 0
  }
}
--> /dmadev/stats_reset,0
{
  "/dmadev/stats_reset": {
    "submitted": 23,
    "completed": 23,
    "errors": 0
  }
}

The rootcause is that the /dmadev/stats_reset don't set the outer parameter "struct rte_tel_data *info"
and return zero.


BTW: although the telemetry mainly used to query, but some reset counter maybe usefull, and it already
exist like: "/eventdev/rxa_stats_reset" and this patchset.


> 
> Thanks,
> /Bruce
> .
>