netdev - Re: [PATCH net] stmmac: reset last TSO segment size after device open

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Date:   Sun, 03 Dec 2017 09:48:25 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     lars.persson@...s.com
Cc:     peppe.cavallaro@...com, alexandre.torgue@...com,
        netdev@...r.kernel.org, larper@...s.com
Subject: Re: [PATCH net] stmmac: reset last TSO segment size after device
 open

From: Lars Persson <lars.persson@...s.com>
Date: Fri,  1 Dec 2017 11:12:44 +0100

> The mss variable tracks the last max segment size sent to the TSO
> engine. We do not update the hardware as long as we receive skb:s with
> the same value in gso_size.
> 
> During a network device down/up cycle (mapped to stmmac_release() and
> stmmac_open() callbacks) we issue a reset to the hardware and it
> forgets the setting for mss. However we did not zero out our mss
> variable so the next transmission of a gso packet happens with an
> undefined hardware setting.
> 
> This triggers a hang in the TSO engine and eventuelly the netdev
> watchdog will bark.
> 
> Fixes: f748be531d70 ("stmmac: support new GMAC4")
> Signed-off-by: Lars Persson <larper@...s.com>

Applied and queued up for -stable, thanks.