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

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Date: Tue, 9 May 2023 13:13:59 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Jiri Pirko <jiri@...nulli.us>, <netdev@...r.kernel.org>
CC: <kuba@...nel.org>, <pabeni@...hat.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <saeedm@...dia.com>, <moshe@...dia.com>
Subject: Re: [patch net 3/3] devlink: fix a deadlock with nested instances
 during namespace remove



On 5/9/2023 3:09 AM, Jiri Pirko wrote:
> 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(-)
> 

Not sure of the patchworks is confused by 3/3 instead of 0/3 on the
cover letter, but the series looks good to me:

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>