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IB/usnic: Fix deadlock
There is a dead lock in usnic ib_register and netdev_notify path.
usnic_ib_discover_pf()
| mutex_lock(&usnic_ib_ibdev_list_lock);
| usnic_ib_device_add();
| ib_register_device()
| usnic_ib_query_port()
| mutex_lock(&us_ibdev->usdev_lock);
| ib_get_eth_speed()
| rtnl_lock()
order of lock: &usnic_ib_ibdev_list_lock -> usdev_lock -> rtnl_lock
rtnl_lock()
| usnic_ib_netdevice_event()
| mutex_lock(&usnic_ib_ibdev_list_lock);
order of lock: rtnl_lock -> &usnic_ib_ibdev_list_lock
Solution is to use the core's lock-free ib_device_get_by_netdev() scheme
to lookup ib_dev while handling netdev & inet events.
Signed-off-by: Parvi Kaustubhi <pkaustub@cisco.com>
Reviewed-by: Govindarajulu Varadarajan <gvaradar@cisco.com>
Reviewed-by: Tanmay Inamdar <tinamdar@cisco.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>