netdev - Re: [PATCH v4 net-next 0/9] Drop rtnl_lock from DSA .port_fdb

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Message-ID: <20211023140518.ecglnaw3quoi7bmr@skbuf>
Date:   Sat, 23 Oct 2021 14:05:19 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        DENG Qingfang <dqfext@...il.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        George McCollister <george.mccollister@...il.com>,
        John Crispin <john@...ozen.org>,
        Aleksander Jan Bajkowski <olek2@...pl>,
        Egil Hjelmeland <privat@...l-hjelmeland.no>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>,
        Ansuel Smith <ansuelsmth@...il.com>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Claudiu Manoil <claudiu.manoil@....com>
Subject: Re: [PATCH v4 net-next 0/9] Drop rtnl_lock from DSA
 .port_fdb_{add,del}

On Fri, Oct 22, 2021 at 09:43:03PM +0300, Vladimir Oltean wrote:
> As mentioned in the RFC posted 2 months ago:
> https://patchwork.kernel.org/project/netdevbpf/cover/20210824114049.3814660-1-vladimir.oltean@nxp.com/
> 
> DSA is transitioning to a driver API where the rtnl_lock is not held
> when calling ds->ops->port_fdb_add() and ds->ops->port_fdb_del().
> Drivers cannot take that lock privately from those callbacks either.
> 
> This change is required so that DSA can wait for switchdev FDB work
> items to finish before leaving the bridge. That change will be made in a
> future patch series.
> 
> A small selftest is provided with the patch set in the hope that
> concurrency issues uncovered by this series, but not spotted by me by
> code inspection, will be caught.
> 
> A status of the existing drivers:
> 
> - mv88e6xxx_port_fdb_add() and mv88e6xxx_port_fdb_del() take
>   mv88e6xxx_reg_lock() so they should be safe.
> 
> - qca8k_fdb_add() and qca8k_fdb_del() take mutex_lock(&priv->reg_mutex)
>   so they should be safe.
> 
> - hellcreek_fdb_add() and hellcreek_fdb_add() take mutex_lock(&hellcreek->reg_lock)
>   so they should be safe.
> 
> - ksz9477_port_fdb_add() and ksz9477_port_fdb_del() take mutex_lock(&dev->alu_mutex)
>   so they should be safe.
> 
> - b53_fdb_add() and b53_fdb_del() did not have locking, so I've added a
>   scheme based on my own judgement there (not tested).
> 
> - felix_fdb_add() and felix_fdb_del() did not have locking, I've added
>   and tested a locking scheme there.
> 
> - mt7530_port_fdb_add() and mt7530_port_fdb_del() take
>   mutex_lock(&priv->reg_mutex), so they should be safe.
> 
> - gswip_port_fdb() did not have locking, so I've added a non-expert
>   locking scheme based on my own judgement (not tested).
> 
> - lan9303_alr_add_port() and lan9303_alr_del_port() take
>   mutex_lock(&chip->alr_mutex) so they should be safe.
> 
> - sja1105_fdb_add() and sja1105_fdb_del() did not have locking, I've
>   added and tested a locking scheme.
> 
> Changes in v3:
> Unlock arl_mutex only once in b53_fdb_dump().
> 
> Changes in v4:
> - Use __must_hold in ocelot and b53
> - Add missing mutex_init in lantiq_gswip
> - Clean up the selftest a bit.
> 
> Vladimir Oltean (9):
>   net: dsa: sja1105: wait for dynamic config command completion on
>     writes too
>   net: dsa: sja1105: serialize access to the dynamic config interface
>   net: mscc: ocelot: serialize access to the MAC table
>   net: dsa: b53: serialize access to the ARL table
>   net: dsa: lantiq_gswip: serialize access to the PCE table
>   net: dsa: introduce locking for the address lists on CPU and DSA ports
>   net: dsa: drop rtnl_lock from dsa_slave_switchdev_event_work
>   selftests: lib: forwarding: allow tests to not require mz and jq
>   selftests: net: dsa: add a stress test for unlocked FDB operations
> 
>  MAINTAINERS                                   |  1 +
>  drivers/net/dsa/b53/b53_common.c              | 40 ++++++--
>  drivers/net/dsa/b53/b53_priv.h                |  1 +
>  drivers/net/dsa/lantiq_gswip.c                | 28 +++++-
>  drivers/net/dsa/sja1105/sja1105.h             |  2 +
>  .../net/dsa/sja1105/sja1105_dynamic_config.c  | 91 ++++++++++++++-----
>  drivers/net/dsa/sja1105/sja1105_main.c        |  1 +
>  drivers/net/ethernet/mscc/ocelot.c            | 53 ++++++++---
>  include/net/dsa.h                             |  1 +
>  include/soc/mscc/ocelot.h                     |  3 +
>  net/dsa/dsa2.c                                |  1 +
>  net/dsa/slave.c                               |  2 -
>  net/dsa/switch.c                              | 76 +++++++++++-----
>  .../drivers/net/dsa/test_bridge_fdb_stress.sh | 47 ++++++++++
>  tools/testing/selftests/net/forwarding/lib.sh | 10 +-
>  15 files changed, 283 insertions(+), 74 deletions(-)
>  create mode 100755 tools/testing/selftests/drivers/net/dsa/test_bridge_fdb_stress.sh
> 
> -- 
> 2.25.1
> 

Please discard this series for now. I'd like to get rid of the useless
sparse __must_hold context attributes.