rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4540/1:b..l
	(detected by 0, t=10502 jiffies, g=14665, q=38)
task:kworker/u4:15   state:R  running task     stack:23416 pid: 4540 ppid:     2 flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5027 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6777
 irqentry_exit+0x53/0x80 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:rcu_is_watching+0x67/0xa0 kernel/rcu/tree.c:1125
Code: 0b 5f 00 48 c7 c3 c8 b2 03 00 49 03 1e 48 89 d8 48 c1 e8 03 42 0f b6 04 38 84 c0 75 1a 8b 03 65 ff 0d 35 56 97 7e 74 08 24 01 <5b> 41 5e 41 5f c3 e8 16 73 95 ff eb f1 89 d9 80 e1 07 80 c1 03 38
RSP: 0018:ffffc900034b7a20 EFLAGS: 00000202
RAX: 0000000000013301 RBX: ffff8880b913b2c8 RCX: ffff8880780c1dc0
RDX: ffff8880780c1dc0 RSI: ffffffff8ad904a0 RDI: ffffffff8ad90460
RBP: ffffc900034b7b50 R08: ffffffff88d340a9 R09: fffffbfff20e2419
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92000696f5e
R13: 00000000000039da R14: ffffffff8c3b4808 R15: dffffc0000000000
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 inet_twsk_purge+0x142/0x9d0 net/ipv4/inet_timewait_sock.c:268
 tcp_sk_exit_batch+0x28/0x90 net/ipv4/tcp_ipv4.c:3231
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x763/0xb60 net/core/net_namespace.c:599
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: rcu_preempt kthread starved for 10426 jiffies! g14665 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:26400 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5027 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
 schedule+0x11b/0x1f0 kernel/sched/core.c:6456
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x2bf/0x1080 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2145
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:108 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:562