net/mlx5e: Convert mlx5 netdevs to instance locking

This patch convert mlx5 to use the new netdev instance lock in addition
to the pre-existing state_lock (and the RTNL).

mlx5e_priv.state_lock was already used throughout mlx5 to protect
against concurrent state modifications on the same netdev, usually in
addition to the RTNL. The new netdev instance lock will eventually
replace it, but for now, it is acquired in addition to the existing
locks in the order RTNL -> instance lock -> state_lock.

All three netdev types handled by mlx5 are converted to the new style of
locking, because they share a lot of code related to initializing
channels and dealing with NAPI, so it's better to convert all three
rather than introduce different assumptions deep in the call stack
depending on the type of device.

Because of the nature of the call graphs in mlx5, it wasn't possible to
incrementally convert parts of the driver to use the new lock, since
either all call paths into NAPI have to possess the new lock if the
*_locked variants are used, or none of them can have the lock.

One area which required extra care is the interaction between closing
channels and devlink health reporter tasks.
Previously, the recovery tasks were unconditionally acquiring the
RTNL, which could lead to deadlocks in these scenarios:

T1: mlx5e_close (== .ndo_stop(), has RTNL) -> mlx5e_close_locked
-> mlx5e_close_channels -> mlx5e_ptp_close
-> mlx5e_ptp_close_queues -> mlx5e_ptp_close_txqsqs
-> mlx5e_ptp_close_txqsq
-> cancel_work_sync(&ptpsq->report_unhealthy_work) waits for

T2: mlx5e_ptpsq_unhealthy_work -> mlx5e_reporter_tx_ptpsq_unhealthy
-> mlx5e_health_report -> devlink_health_report
-> devlink_health_reporter_recover
-> mlx5e_tx_reporter_ptpsq_unhealthy_recover which does:
rtnl_lock();   => Deadlock.

Another similar instance of this is:
T1: mlx5e_close (== .ndo_stop(), has RTNL) -> mlx5e_close_locked
-> mlx5e_close_channels -> mlx5e_ptp_close
-> mlx5e_ptp_close_queues -> mlx5e_ptp_close_txqsqs
-> mlx5e_ptp_close_txqsq
-> cancel_work_sync(&sq->recover_work) waits for

T2: mlx5e_tx_err_cqe_work -> mlx5e_reporter_tx_err_cqe
-> mlx5e_health_report -> devlink_health_report
-> devlink_health_reporter_recover
-> mlx5e_tx_reporter_err_cqe_recover which does:
rtnl_lock();   => Another deadlock.

Fix that by using the same pattern previously done in
mlx5e_tx_timeout_work, where the RTNL was repeatedly tried to be
acquired until either:
a) it is successfully acquired or
b) there's no need for the work to be done any more (channel is being
closed).

Now, for all three recovery tasks, the instance lock is repeatedly tried
to be acquired until successful or the channel/SQ is closed.
As a side-effect, drop the !test_bit(MLX5E_STATE_OPENED, &priv->state)
check from mlx5e_tx_timeout_work, it's weaker than
!test_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state) and unnecessary.

Future patches will introduce new call paths (from netdev queue
management ops) which can close channels (and call cancel_work_sync on
the recovery tasks) without the RTNL lock and only with the netdev
instance lock.

Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1747829342-1018757-6-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions