Re: AW: AW: AW: [PATCH] can: isotp: omit unintended hrtimer restart on socket release

[Oliver Hartkopp <socketcan@hartkopp.net>]

Hi Sven,

On 30.08.21 09:55, Sven Schuchmann wrote:

>> but if I compare the candumps I can see:
>> with the patch:
>>
>>   (000.000008)  vcan0  714   [8]  2F 01 01 01 01 01 01 01
>>   (000.000209)  vcan0  77E   [8]  30 0F 00 AA AA AA AA AA
>>   (000.000061)  vcan0  714   [8]  20 01 01 01 01 01 01 01
>>
>> and without:
>>
>>   (000.000004)  vcan0  714   [8]  2F 01 01 01 01 01 01 01
>>   (000.000069)  vcan0  77E   [8]  30 0F 00 AA AA AA AA AA
>>   (000.000017)  vcan0  714   [8]  20 01 01 01 01 01 01 01
>>
>> sorry, I missed that: Over here the delay seems to be in
>> the FC and not in the CF after the FC. This is what is
>> different compared to the real hardware.
>>
>> So to me it seems that the rcu implementation
>> has changed on the way from 5.10 to 5.14?
> 
> Just checked with a 5.14.0-rc6 which contains the patch, same result:
> 
>     93 / curr:  143 / min:  129 / max:  200 / avg:  156.2
>     94 / curr:  144 / min:  129 / max:  200 / avg:  156.0
>     95 / curr:  141 / min:  129 / max:  200 / avg:  155.9
>     96 / curr:  171 / min:  129 / max:  200 / avg:  156.0
>     97 / curr:  138 / min:  129 / max:  200 / avg:  155.8
>     98 / curr:  137 / min:  129 / max:  200 / avg:  155.6
> 
>   (000.000011)  vcan0  714   [8]  2B 01 01 01 01 01 01 01
>   (000.000193)  vcan0  77E   [8]  30 0F 00 AA AA AA AA AA
>   (000.000037)  vcan0  714   [8]  2C 01 01 01 01 01 01 01
> 
> So maybe there is something wrong on the rpi?

I see a similar difference on my i7-8650U system:

"5" without and "65" with the patch.

The problem remains to be the added time that is now introduced at 
socket close time with the rcu_synchronize().

In your script you are waiting for isotprecv process to finally end with:

	wait $rxpid

And that's the expectable effect ...

It looks like the script works fine without the 'wait' code (which does 
not wait for the process removal then).

@mkl: I assume we have to live with that increased time at socket close 
for security reasons, right?

Best regards,
Oliver

ps. Btw IMO a C program is still the better approach here. 
isotp[send|recv] open/close the sockets for each PDU in the given setup :-/