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authorParav Pandit <parav@nvidia.com>2020-10-26 15:43:59 +0200
committerJason Gunthorpe <jgg@nvidia.com>2020-10-26 19:18:19 -0300
commitfbdd0049d98d44914fc57d4b91f867f4996c787b (patch)
treeec7b77d3cfd8055fdef93031a3185171c2fe08cd /include
parentedebc8407b8891ec0ea9ca4089f3d3343a5e50dd (diff)
RDMA/mlx5: Fix devlink deadlock on net namespace deletion
When a mlx5 core devlink instance is reloaded in different net namespace, its associated IB device is deleted and recreated. Example sequence is: $ ip netns add foo $ devlink dev reload pci/0000:00:08.0 netns foo $ ip netns del foo mlx5 IB device needs to attach and detach the netdevice to it through the netdev notifier chain during load and unload sequence. A below call graph of the unload flow. cleanup_net() down_read(&pernet_ops_rwsem); <- first sem acquired ops_pre_exit_list() pre_exit() devlink_pernet_pre_exit() devlink_reload() mlx5_devlink_reload_down() mlx5_unload_one() [...] mlx5_ib_remove() mlx5_ib_unbind_slave_port() mlx5_remove_netdev_notifier() unregister_netdevice_notifier() down_write(&pernet_ops_rwsem);<- recurrsive lock Hence, when net namespace is deleted, mlx5 reload results in deadlock. When deadlock occurs, devlink mutex is also held. This not only deadlocks the mlx5 device under reload, but all the processes which attempt to access unrelated devlink devices are deadlocked. Hence, fix this by mlx5 ib driver to register for per net netdev notifier instead of global one, which operats on the net namespace without holding the pernet_ops_rwsem. Fixes: 4383cfcc65e7 ("net/mlx5: Add devlink reload") Link: https://lore.kernel.org/r/20201026134359.23150-1-parav@nvidia.com Signed-off-by: Parav Pandit <parav@nvidia.com> Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mlx5/driver.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
index add85094f9a5..0f23e1ed5e71 100644
--- a/include/linux/mlx5/driver.h
+++ b/include/linux/mlx5/driver.h
@@ -1213,4 +1213,22 @@ static inline bool mlx5_is_roce_enabled(struct mlx5_core_dev *dev)
return val.vbool;
}
+/**
+ * mlx5_core_net - Provide net namespace of the mlx5_core_dev
+ * @dev: mlx5 core device
+ *
+ * mlx5_core_net() returns the net namespace of mlx5 core device.
+ * This can be called only in below described limited context.
+ * (a) When a devlink instance for mlx5_core is registered and
+ * when devlink reload operation is disabled.
+ * or
+ * (b) during devlink reload reload_down() and reload_up callbacks
+ * where it is ensured that devlink instance's net namespace is
+ * stable.
+ */
+static inline struct net *mlx5_core_net(struct mlx5_core_dev *dev)
+{
+ return devlink_net(priv_to_devlink(dev));
+}
+
#endif /* MLX5_DRIVER_H */

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