netdev - Re: [PATCH v2] net: dp83640: expire old TX-skb

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Date:   Fri, 1 Feb 2019 18:38:13 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] net: dp83640: expire old TX-skb

On Fri, Feb 01, 2019 at 10:09:18PM +0100, Sebastian Andrzej Siewior wrote:
> During sendmsg() a cloned skb is saved via dp83640_txtstamp() in
> ->tx_queue. After the NIC sends this packet, the PHY will reply with a
> timestamp for that TX packet. If the cable is pulled at the right time I
> don't see that packet. It might gets flushed as part of queue shutdown
> on NIC's side.
> Once the link is up again then after the next sendmsg() we enqueue
> another skb in dp83640_txtstamp() and have two on the list. Then the PHY
> will send a reply and decode_txts() attaches it to the first skb on the
> list.
> No crash occurs since refcounting works but we are one packet behind.
> linuxptp/ptp4l usually closes the socket and opens a new one (in such a
> timeout case) so those "stale" replies never get there. However it does
> not resume normal operation anymore.
> 
> Purge old skbs in decode_txts().
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de>

Acked-by: Richard Cochran <richardcochran@...il.com>