netdev - Re: [RFC] net: dp83640: expire old TX-skb

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Message-ID: <20190201210431.tskgqrrxfrz6ljul@linutronix.de>
Date:   Fri, 1 Feb 2019 22:04:31 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org
Subject: Re: [RFC] net: dp83640: expire old TX-skb

On 2019-01-30 20:26:06 [-0800], Richard Cochran wrote:
> Thanks for the detailed explanation.  This sounds like a really rare
> bug, but maybe you guys were able to trigger it reliably?

More or less reliably, yes. I had two switches (for the uplink of the
PHY) and a third for my regular network during testing. I had one
combination which triggered the issue after no longer than the fifth
disconnect and another one which happily survived _a lot_ longer. 

> > Purge old skbs in decode_txts().
> 
> It is too bad that the Tx timestamp from the HW doesn't provide
> matching fields.  Using the timeout is probably the best that we can
> do.

yeah. I've been looking around and it seems there is nothing. And since
that packet from the PHY is sent very seen usually shortly after the
transmit I went for something similar that is already done the RX path.

Sebastian