mlx4: Move the bond work to the core driver
Function mlx4_en_queue_bond_work() is used in mlx4_en to start a bond reconfiguration. It gathers data about a new port map setting, takes a reference on the netdev that triggered the change and queues a work object on mlx4_en_priv.mdev.workqueue to perform the operation. The scheduled work is mlx4_en_bond_work() which calls mlx4_bond()/mlx4_unbond() and consequently mlx4_do_bond(). At the same time, function mlx4_change_port_types() in mlx4_core might be invoked to change the port type configuration. As part of its logic, it re-registers the whole device by calling mlx4_unregister_device(), followed by mlx4_register_device(). The two operations can result in concurrent access to the data about currently active interfaces on the device. Functions mlx4_register_device() and mlx4_unregister_device() lock the intf_mutex to gain exclusive access to this data. The current implementation of mlx4_do_bond() doesn't do that which could result in an unexpected behavior. An updated version of mlx4_do_bond() for use with an auxiliary bus goes and locks the intf_mutex when accessing a new auxiliary device array. However, doing so can then result in the following deadlock: * A two-port mlx4 device is configured as an Ethernet bond. * One of the ports is changed from eth to ib, for instance, by writing into a mlx4_port<x> sysfs attribute file. * mlx4_change_port_types() is called to update port types. It invokes mlx4_unregister_device() to unregister the device which locks the intf_mutex and starts removing all associated interfaces. * Function mlx4_en_remove() gets invoked and starts destroying its first netdev. This triggers mlx4_en_netdev_event() which recognizes that the configured bond is broken. It runs mlx4_en_queue_bond_work() which takes a reference on the netdev. Removing the netdev now cannot proceed until the work is completed. * Work function mlx4_en_bond_work() gets scheduled. It calls mlx4_unbond() -> mlx4_do_bond(). The latter function tries to lock the intf_mutex but that is not possible because it is held already by mlx4_unregister_device(). This particular case could be possibly solved by unregistering the mlx4_en_netdev_event() notifier in mlx4_en_remove() earlier, but it seems better to decouple mlx4_en more and break this reference order. Avoid then this scenario by recognizing that the bond reconfiguration operates only on a mlx4_dev. The logic to queue and execute the bond work can be moved into the mlx4_core driver. Only a reference on the respective mlx4_dev object is needed to be taken during the work's lifetime. This removes a call from mlx4_en that can directly result in needing to lock the intf_mutex, it remains a privilege of the core driver. Signed-off-by:Petr Pavlu <petr.pavlu@suse.com> Tested-by:
Leon Romanovsky <leonro@nvidia.com> Reviewed-by:
Tariq Toukan <tariqt@nvidia.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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