INFO: task kworker/u4:4:2566 blocked for more than 143 seconds.
      Not tainted 5.3.0-rc3+ #99
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:4    D24952  2566      2 0x80004000
Workqueue: netns cleanup_net
Call Trace:
 context_switch kernel/sched/core.c:3254 [inline]
 __schedule+0x755/0x1580 kernel/sched/core.c:3880
 schedule+0xa8/0x270 kernel/sched/core.c:3944
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4003
 __mutex_lock_common kernel/locking/mutex.c:1007 [inline]
 __mutex_lock+0x7b0/0x13c0 kernel/locking/mutex.c:1077
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1092
 rtnl_lock+0x17/0x20 net/core/rtnetlink.c:72
 ip6gre_exit_batch_net+0x8e/0x750 net/ipv6/ip6_gre.c:1601
 ops_exit_list.isra.0+0xfc/0x150 net/core/net_namespace.c:175
 cleanup_net+0x4e2/0xa70 net/core/net_namespace.c:594
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
INFO: task kworker/1:14:18137 blocked for more than 145 seconds.