linux-kernel - Re: [RFC PATCH net 3/5] net: dsa: hellcreek: be compatible with masters which unregister on shutdown

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Message-ID: <874kan1sw5.fsf@kurt>
Date:   Tue, 14 Sep 2021 10:08:26 +0200
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        George McCollister <george.mccollister@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Lino Sanfilippo <LinoSanfilippo@....de>
Subject: Re: [RFC PATCH net 3/5] net: dsa: hellcreek: be compatible with
 masters which unregister on shutdown

On Sun Sep 12 2021, Vladimir Oltean wrote:
> Since commit 2f1e8ea726e9 ("net: dsa: link interfaces with the DSA
> master to get rid of lockdep warnings"), DSA gained a requirement which
> it did not fulfill, which is to unlink itself from the DSA master at
> shutdown time.
>
> Since the hellcreek driver was introduced after the bad commit, it has
> never worked with DSA masters which decide to unregister their
> net_device on shutdown, effectively hanging the reboot process.
>
> Hellcreek is a platform device driver, so we probably cannot have the
> oddities of ->shutdown and ->remove getting both called for the exact
> same struct device. But to be in line with the pattern from the other
> device drivers which are on slow buses, implement the same "if this then
> not that" pattern of either running the ->shutdown or the ->remove hook.
> The driver's current ->remove implementation makes that very easy
> because it already zeroes out its device_drvdata on ->remove.
>
> Fixes: e4b27ebc780f ("net: dsa: Add DSA driver for Hirschmann Hellcreek switches")
> Link: https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@gmx.de/
> Reported-by: Lino Sanfilippo <LinoSanfilippo@....de>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Acked-by: Kurt Kanzenbach <kurt@...utronix.de>

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