Hello, I find a scenario may cause deadlock of rtnl_lock as follows: 1. CPU1 add rtnl_lock and wait kworker finished. CPU1 add rtnl_lock before call unregister_netdevice_queue() and then wait sport->work(function srpt_refresh_port_work) finished in srpt_remove_one(). [<0>] __switch_to+0x94/0xe8 [<0>] __flush_work+0x128/0x280 [<0>] __cancel_work_timer+0x13c/0x1b0 [<0>] cancel_work_sync+0x24/0x30 [<0>] srpt_remove_one+0xf0/0x530 [ib_srpt] [<0>] ib_unregister_device+0x124/0x230 [ib_core] [<0>] rxe_unregister_device+0x30/0x40 [rdma_rxe] [<0>] rxe_remove+0x20/0x50 [rdma_rxe] [<0>] rxe_notify+0xe8/0x150 [rdma_rxe] [<0>] notifier_call_chain+0x5c/0xa0 [<0>] raw_notifier_call_chain+0x3c/0x50 [<0>] call_netdevice_notifiers_info+0x3c/0x80 [<0>] rollback_registered_many+0x35c/0x568 [<0>] rollback_registered+0x68/0xb0 [<0>] unregister_netdevice_queue+0xc0/0x110 [<0>] __tun_detach+0x25c/0x2a0 [tun] [<0>] tun_chr_close+0x30/0x60 [tun] [<0>] __fput+0xa4/0x1e0 [<0>] ____fput+0x20/0x30 [<0>] task_work_run+0xc0/0xf8 [<0>] do_notify_resume+0x12c/0x138 [<0>] work_pending+0x8/0x10 [<0>] 0xffffffffffffffff 2. CPU2 run sport->work and wait for rxe->usdev_lock. CPU2 run work(sport->work function: srpt_refresh_port_work) and wait for rxe->usdev_lock in rxe_query_port(). [<0>] __switch_to+0x94/0xe8 [<0>] rxe_query_port+0x6c/0xd0 [rdma_rxe] [<0>] ib_query_port+0x84/0x120 [ib_core] [<0>] srpt_refresh_port+0xa4/0x1b8 [ib_srpt] [<0>] srpt_refresh_port_work+0x20/0x30 [ib_srpt] [<0>] process_one_work+0x1b4/0x3f8 [<0>] worker_thread+0x54/0x470 [<0>] kthread+0x134/0x138 [<0>] ret_from_fork+0x10/0x18 [<0>] 0xffffffffffffffff 3. CPU3 add rxe->usdev_lock and wait for rtnl_lock. CPU3 run ib_cache_task work and add rxe->usdev_lock, then wait for rtnl_lock is unlocked. [<0>] __switch_to+0x94/0xe8 [<0>] rtnl_lock+0x1c/0x28 [<0>] ib_get_eth_speed+0x78/0x1c0 [ib_core] [<0>] rxe_query_port+0x80/0xd0 [rdma_rxe] [<0>] ib_query_port+0x84/0x120 [ib_core] [<0>] ib_cache_update.part.7+0x74/0x388 [ib_core] [<0>] ib_cache_task+0x68/0x80 [ib_core] [<0>] process_one_work+0x1b4/0x3f8 [<0>] worker_thread+0x54/0x470 [<0>] kthread+0x134/0x138 [<0>] ret_from_fork+0x10/0x18 [<0>] 0xffffffffffffffff So, deadlock is produced, that is, CPU1 wait for CPU2 work is finished, CPU2 wait for CPU3 unlock rxe->usdev_lock, CPU3 wait for CPU1 unlock rtnl_lock. I don't know how to solve it. Thanks, Yiwen.
