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Subject: Re: [bug, bisected] pfifo_fast causes packet reordering
From:   Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
To:     John Fastabend <john.fastabend@gmail.com>,
        Dave Taht <dave.taht@gmail.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        "linux-can@vger.kernel.org" <linux-can@vger.kernel.org>,
        Martin Elshuber <martin.elshuber@theobroma-systems.com>
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Message-ID: <00cc2d41-6861-9a9c-603f-ba8013b2e2ce@theobroma-systems.com>
Date:   Wed, 21 Mar 2018 11:01:17 +0100
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On 16.03.18 11:26, Jakob Unterwurzacher wrote:
> On 15.03.18 23:30, John Fastabend wrote:
>>> I have reproduced it using two USB network cards connected to each 
>>> other. The test tool sends UDP packets containing a counter and 
>>> listens on the other interface, it is available at
>>> https://github.com/jakob-tsd/pfifo_stress/blob/master/pfifo_stress.py
>>
>> Great thanks, can you also run this with taskset to bind to
>> a single CPU,
>>
>>   # taskset 0x1 ./pifof_stress.py
>>
>> And let me know if you still see the OOO.
> 
> Interesting. Looks like it depends on which core it runs on. CPU0 is 
> clean, CPU1 is not.

So we are at v4.16-rc6 now - have you managed to reproduce this is or 
should I try to get the revert correct?

Best regards,
Jakob