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8f7b00307b
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> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.