rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P16391/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=119341, q=134 ncpus=2)
task:kworker/u4:9    state:R  running task     stack:27328 pid:16391 ppid:2      flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5307 [inline]
 __schedule+0xc91/0x5770 kernel/sched/core.c:6625
 preempt_schedule_irq+0x52/0x90 kernel/sched/core.c:6937
 irqentry_exit+0x35/0x80 kernel/entry/common.c:433
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
RIP: 0010:lock_acquire+0x1f3/0x520 kernel/locking/lockdep.c:5637
Code: d8 9d 7e 83 f8 01 0f 85 b9 02 00 00 9c 58 f6 c4 02 0f 85 a4 02 00 00 48 83 7c 24 08 00 74 01 fb 48 b8 00 00 00 00 00 fc ff df <48> 01 c3 48 c7 03 00 00 00 00 48 c7 43 08 00 00 00 00 48 8b 84 24
RSP: 0018:ffffc90015fbfa30 EFLAGS: 00000206
RAX: dffffc0000000000 RBX: 1ffff92002bf7f48 RCX: 64158163e74cc960
RDX: 1ffff11005f17c3e RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff914d2b87
R10: fffffbfff229a570 R11: 1ffff11003ef8432 R12: 0000000000000002
R13: 0000000000000000 R14: ffffffff8c7955c0 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:327 [inline]
 rcu_read_lock include/linux/rcupdate.h:773 [inline]
 inet_twsk_purge+0x132/0x900 net/ipv4/inet_timewait_sock.c:292
 ops_exit_list+0x125/0x170 net/core/net_namespace.c:174
 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613
 process_one_work+0x991/0x15c0 kernel/workqueue.c:2390
 worker_thread+0x669/0x1090 kernel/workqueue.c:2537
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
 </TASK>
rcu: rcu_preempt kthread starved for 9552 jiffies! g119341 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:28584 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5307 [inline]
 __schedule+0xc91/0x5770 kernel/sched/core.c:6625
 schedule+0xde/0x1a0 kernel/sched/core.c:6701
 schedule_timeout+0x14e/0x2b0 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x190/0x910 kernel/rcu/tree.c:1608
 rcu_gp_kthread+0x23a/0x360 kernel/rcu/tree.c:1807
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt+0x40/0x50 drivers/acpi/processor_idle.c:112