netdev - Re: [PATCH net-next v3 04/11] mlx4: Replace the mlx4_interface.event callback with a notifier

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Date: Tue, 22 Aug 2023 17:04:03 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: tariqt@...dia.com, yishaih@...dia.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	jgg@...pe.ca, netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 04/11] mlx4: Replace the mlx4_interface.event
 callback with a notifier

On Mon, Aug 21, 2023 at 03:12:18PM +0200, Petr Pavlu wrote:
> Use a notifier to implement mlx4_dispatch_event() in preparation to
> switch mlx4_en and mlx4_ib to be an auxiliary device.
> 
> A problem is that if the mlx4_interface.event callback was replaced with
> something as mlx4_adrv.event then the implementation of
> mlx4_dispatch_event() would need to acquire a lock on a given device
> before executing this callback. That is necessary because otherwise
> there is no guarantee that the associated driver cannot get unbound when
> the callback is running. However, taking this lock is not possible
> because mlx4_dispatch_event() can be invoked from the hardirq context.
> Using an atomic notifier allows the driver to accurately record when it
> wants to receive these events and solves this problem.
> 
> A handler registration is done by both mlx4_en and mlx4_ib at the end of
> their mlx4_interface.add callback. This matches the current situation
> when mlx4_add_device() would enable events for a given device
> immediately after this callback, by adding the device on the
> mlx4_priv.list.
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@...e.com>
> Tested-by: Leon Romanovsky <leonro@...dia.com>
> Acked-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  drivers/infiniband/hw/mlx4/main.c            | 40 +++++++++++++-------
>  drivers/infiniband/hw/mlx4/mlx4_ib.h         |  2 +
>  drivers/net/ethernet/mellanox/mlx4/en_main.c | 26 +++++++++----
>  drivers/net/ethernet/mellanox/mlx4/intf.c    | 24 ++++++++----
>  drivers/net/ethernet/mellanox/mlx4/main.c    |  2 +
>  drivers/net/ethernet/mellanox/mlx4/mlx4.h    |  2 +
>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h |  2 +
>  include/linux/mlx4/driver.h                  |  8 +++-
>  8 files changed, 75 insertions(+), 31 deletions(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>