linux-kernel - Re: [PATCH 0/3] Fix for KSZ DSA switch shutdown

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Date:   Sun, 12 Sep 2021 22:19:24 +0200
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Vladimir Oltean <olteanv@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>, p.rosenberger@...bus.com,
        woojung.huh@...rochip.com, UNGLinuxDriver@...rochip.com,
        vivien.didelot@...il.com, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Fix for KSZ DSA switch shutdown


Hi,

On 10.09.21 at 16:58, Vladimir Oltean wrote:
> On Fri, Sep 10, 2021 at 01:51:56PM +0200, Andrew Lunn wrote:
>>> It does not really scale but we also don't have that many DSA masters to
>>> support, I believe I can name them all: bcmgenet, stmmac, bcmsysport, enetc,
>>> mv643xx_eth, cpsw, macb.
>>
>> fec, mvneta, mvpp2, i210/igb.
>
> I can probably double that list only with Freescale/NXP Ethernet
> drivers, some of which are not even submitted to mainline. To name some
> mainline drivers: gianfar, dpaa-eth, dpaa2-eth, dpaa2-switch, ucc_geth.
> Also consider that DSA/switchdev drivers can also be DSA masters of
> their own, we have boards doing that too.
>
> Anyway, I've decided to at least try and accept the fact that DSA
> masters will unregister their net_device on shutdown, and attempt to do
> something sane for all DSA switches in that case.
>
> Attached are two patches (they are fairly big so I won't paste them
> inline, and I would like initial feedback before posting them to the
> list).
>
> As mentioned in those patches, the shutdown ordering guarantee is still
> very important, I still have no clue what goes on there, what we need to
> do, etc.
>

I tested these patches with my 5.10 kernel (based on Gregs 5.10.27 stable
kernel) and while I do not see the message "unregister_netdevice: waiting
for eth0 to become free. Usage count = 2." any more the shutdown/reboot hangs, too.
After a few attempts without any error messages on the console I was able to get a
 stack trace. Something still seems to go wrong in bcm2835_spi_shutdown() (see attachment).
I have not had the time yet to investigate this further (or to test the patches
 with a newer kernel).

Regards,
Lino

Download attachment "shutdown_failure.jpg" of type "image/jpeg" (3885442 bytes)