[PATCH v2] net/pcap: fix timeout of stopping device

[Ferruh Yigit]

On 9/21/2022 8:14 AM, Zhou, YidingX wrote:
> 
> 
>> -----Original Message-----
>> From: Stephen Hemminger <stephen at networkplumber.org>
>> Sent: Tuesday, September 6, 2022 10:58 PM
>> To: Zhou, YidingX <yidingx.zhou at intel.com>
>> Cc: dev at dpdk.org; Zhang, Qi Z <qi.z.zhang at intel.com>; Burakov, Anatoly
>> <anatoly.burakov at intel.com>; He, Xingguang <xingguang.he at intel.com>;
>> stable at dpdk.org
>> Subject: Re: [PATCH v2] net/pcap: fix timeout of stopping device
>>
>> On Tue,  6 Sep 2022 16:05:11 +0800
>> Yiding Zhou <yidingx.zhou at intel.com> wrote:
>>
>>> The pcap file will be synchronized to the disk when stopping the device.
>>> It takes a long time if the file is large that would cause the 'detach
>>> sync request' timeout when the device is closed under multi-process
>>> scenario.
>>>
>>> This commit fixes the issue by using alarm handler to release dumper.
>>>
>>> Fixes: 0ecfb6c04d54 ("net/pcap: move handler to process private")
>>> Cc: stable at dpdk.org
>>>
>>> Signed-off-by: Yiding Zhou <yidingx.zhou at intel.com>
>>
>>
>> I think you need to redesign the handshake if this the case.
>> Forcing 30 second delay at the end of all uses of pcap is not acceptable.
> 
> @Zhang, Qi Z Do we need to redesign the handshake to fix this?

Hi Yiding,

Your approach works, but Stephen's comment is to not add this delay by 
default, because this delay is not always required.

Can you please provide more details on multi-process communication and 
call trace, to help us think about a solution to address this issue in a 
more generic way (not just for pcap but for any case device close takes 
more than multi-process timeout)?