netdev - Re: [BUG] pfifo_fast may cause out-of-order CAN frame transmission

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Message-ID: <ef6b4e00-75fe-70f6-6b57-7bdbaa1aac33@pengutronix.de>
Date:   Tue, 4 Feb 2020 17:25:38 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-can@...r.kernel.org,
        Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [BUG] pfifo_fast may cause out-of-order CAN frame transmission

Hello Paolo,

On 1/20/20 5:06 PM, Ahmad Fatoum wrote:
> Hello Paolo,
> 
> On 1/16/20 1:40 PM, Paolo Abeni wrote:
>> I'm sorry for this trial & error experience. I tried to reproduce the
>> issue on top of the vcan virtual device, but it looks like it requires
>> the timing imposed by a real device, and it's missing here (TL;DR: I
>> can't reproduce the issue locally).
> 
> No worries. I don't mind testing.
> 
>>
>> Code wise, the 2nd patch closed a possible race, but it dumbly re-
>> opened the one addressed by the first attempt - the 'empty' field must
>> be cleared prior to the trylock operation, or we may end-up with such
>> field set and the queue not empty.
>>
>> So, could you please try the following code?
> 
> Unfortunately, I still see observe reodering.

Any news?

Thanks
Ahmad

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