[RFC PATCH net 0/5] Make DSA switch drivers compatible with masters which unregister on shutdown

[Vladimir Oltean]

It was reported by Lino here:

https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@xxxxxx/

that when the DSA master attempts to unregister its net_device on
shutdown, DSA should prevent that operation from succeeding because it
holds a reference to it. This hangs the shutdown process.

This issue was essentially introduced in commit 2f1e8ea726e9 ("net: dsa:
link interfaces with the DSA master to get rid of lockdep warnings").
The present series patches all DSA drivers to handle that case,
depending on whether those drivers were introduced before or after the
offending commit, a different Fixes: tag is specified for them.

The approach taken by this series solves the issue in essentially the
same way as Lino's patches, except for three key differences:

- this series takes a more minimal approach in what is done on shutdown,
  we do not attempt a full tree teardown as that is not strictly
  necessary. I might revisit this if there are compelling reasons to do
  otherwise

- this series fixes the issues for all DSA drivers, not just KSZ9897

- this series works even if the ->remove driver method gets called for
  the same device too, not just ->shutdown. This is really possible to
  happen for SPI device drivers, and potentially possible for other bus
  device drivers too.

Vladimir Oltean (5):
  net: mdio: introduce a shutdown method to mdio device drivers
  net: dsa: be compatible with masters which unregister on shutdown
  net: dsa: hellcreek: be compatible with masters which unregister on
    shutdown
  net: dsa: microchip: ksz8863: be compatible with masters which
    unregister on shutdown
  net: dsa: xrs700x: be compatible with masters which unregister on
    shutdown

 drivers/net/dsa/b53/b53_mdio.c             | 21 +++++++++-
 drivers/net/dsa/b53/b53_mmap.c             | 13 ++++++
 drivers/net/dsa/b53/b53_priv.h             |  5 +++
 drivers/net/dsa/b53/b53_spi.c              | 13 ++++++
 drivers/net/dsa/b53/b53_srab.c             | 21 +++++++++-
 drivers/net/dsa/bcm_sf2.c                  | 12 ++++++
 drivers/net/dsa/dsa_loop.c                 | 22 ++++++++++-
 drivers/net/dsa/hirschmann/hellcreek.c     | 16 ++++++++
 drivers/net/dsa/lan9303-core.c             |  6 +++
 drivers/net/dsa/lan9303.h                  |  1 +
 drivers/net/dsa/lan9303_i2c.c              | 24 +++++++++--
 drivers/net/dsa/lan9303_mdio.c             | 15 +++++++
 drivers/net/dsa/lantiq_gswip.c             | 18 +++++++++
 drivers/net/dsa/microchip/ksz8795_spi.c    | 11 +++++-
 drivers/net/dsa/microchip/ksz8863_smi.c    | 13 ++++++
 drivers/net/dsa/microchip/ksz9477_i2c.c    | 14 ++++++-
 drivers/net/dsa/microchip/ksz9477_spi.c    |  8 +++-
 drivers/net/dsa/mt7530.c                   | 18 +++++++++
 drivers/net/dsa/mv88e6060.c                | 18 +++++++++
 drivers/net/dsa/mv88e6xxx/chip.c           | 22 ++++++++++-
 drivers/net/dsa/ocelot/felix_vsc9959.c     | 20 +++++++++-
 drivers/net/dsa/ocelot/seville_vsc9953.c   | 20 +++++++++-
 drivers/net/dsa/qca/ar9331.c               | 18 +++++++++
 drivers/net/dsa/qca8k.c                    | 18 +++++++++
 drivers/net/dsa/realtek-smi-core.c         | 20 +++++++++-
 drivers/net/dsa/sja1105/sja1105_main.c     | 21 +++++++++-
 drivers/net/dsa/vitesse-vsc73xx-core.c     |  6 +++
 drivers/net/dsa/vitesse-vsc73xx-platform.c | 22 ++++++++++-
 drivers/net/dsa/vitesse-vsc73xx-spi.c      | 22 ++++++++++-
 drivers/net/dsa/vitesse-vsc73xx.h          |  1 +
 drivers/net/dsa/xrs700x/xrs700x.c          |  6 +++
 drivers/net/dsa/xrs700x/xrs700x.h          |  1 +
 drivers/net/dsa/xrs700x/xrs700x_i2c.c      | 18 +++++++++
 drivers/net/dsa/xrs700x/xrs700x_mdio.c     | 18 +++++++++
 drivers/net/phy/mdio_device.c              | 11 ++++++
 include/linux/mdio.h                       |  3 ++
 include/net/dsa.h                          |  1 +
 net/dsa/dsa2.c                             | 46 ++++++++++++++++++++++
 38 files changed, 539 insertions(+), 24 deletions(-)

-- 
2.25.1