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