netdev - [patch net 3/3] devlink: fix a deadlock with nested instances during namespace remove

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Date: Tue,  9 May 2023 12:09:36 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: netdev@...r.kernel.org
Cc: kuba@...nel.org,
	pabeni@...hat.com,
	davem@...emloft.net,
	edumazet@...gle.com,
	jacob.e.keller@...el.com,
	saeedm@...dia.com,
	moshe@...dia.com
Subject: [patch net 3/3] devlink: fix a deadlock with nested instances during namespace remove

From: Jiri Pirko <jiri@...dia.com>

The commit 565b4824c39f ("devlink: change port event netdev notifier
from per-net to global") changed original per-net notifier to be global
which fixed the issue of non-receiving events of netdev uninit if that
moved to a different namespace. That worked fine in -net tree.

However, later on when commit ee75f1fc44dd ("net/mlx5e: Create
separate devlink instance for ethernet auxiliary device") and
commit 72ed5d5624af ("net/mlx5: Suspend auxiliary devices only in
case of PCI device suspend") were merged, a deadlock was introduced
when removing a namespace with devlink instance with another nested
instance.

Here there is the bad flow example resulting in deadlock with mlx5:
net_cleanup_work -> cleanup_net (takes down_read(&pernet_ops_rwsem) ->
devlink_pernet_pre_exit() -> devlink_reload() ->
mlx5_devlink_reload_down() -> mlx5_unload_one_devl_locked() ->
mlx5_detach_device() -> del_adev() -> mlx5e_remove() ->
mlx5e_destroy_devlink() -> devlink_free() ->
unregister_netdevice_notifier() (takes down_write(&pernet_ops_rwsem)

Steps to reproduce:
$ modprobe mlx5_core
$ ip netns add ns1
$ devlink dev reload pci/0000:08:00.0 netns ns1
$ ip netns del ns1

The first two patches are just dependencies of the last one, which is
actually fixing the issue. It converts the notifier to per per-net
again. But this time also per-devlink_port and setting to follow
the netdev to different namespace.

Jiri Pirko (3):
  net: allow to ask per-net netdevice notifier to follow netdev
    dynamically
  devlink: make netdev notifier per-port
  devlink: change port event netdev notifier to be per-net and following
    netdev

 include/linux/netdevice.h   |  6 +++++
 include/net/devlink.h       |  2 ++
 net/core/dev.c              | 34 +++++++++++++++++++++++-----
 net/devlink/core.c          |  9 --------
 net/devlink/devl_internal.h |  4 ----
 net/devlink/leftover.c      | 45 ++++++++++++++++++++++++++-----------
 6 files changed, 69 insertions(+), 31 deletions(-)

-- 
2.39.2