rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P14911/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=94557, q=165 ncpus=2)
task:kworker/u4:0    state:R  running task     stack:23000 pid:14911 ppid:2      flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1873/0x48f0 kernel/sched/core.c:6710
 preempt_schedule_irq+0xfb/0x1b0 kernel/sched/core.c:7022
 irqentry_exit+0x57/0x80 kernel/entry/common.c:433
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
RIP: 0010:lock_acquire+0x25a/0x520 kernel/locking/lockdep.c:5765
Code: 2b 00 74 08 4c 89 f7 e8 c4 7a 79 00 f6 44 24 61 02 0f 85 84 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc900167178a0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff92002ce2f20 RCX: ffffffff816b2607
RDX: 0000000000000000 RSI: ffffffff8b0aa940 RDI: ffffffff8b58ac60
RBP: ffffc90016717a00 R08: dffffc0000000000 R09: 1ffffffff20f6860
R10: dffffc0000000000 R11: fffffbfff20f6861 R12: 1ffff92002ce2f1c
R13: dffffc0000000000 R14: ffffc90016717900 R15: 0000000000000246
 rcu_lock_acquire+0x2e/0x40 include/linux/rcupdate.h:303
 rcu_read_lock include/linux/rcupdate.h:749 [inline]
 inet_twsk_purge+0x128/0xad0 net/ipv4/inet_timewait_sock.c:292
 ops_exit_list net/core/net_namespace.c:175 [inline]
 cleanup_net+0x767/0xb80 net/core/net_namespace.c:614
 process_one_work+0x92c/0x12c0 kernel/workqueue.c:2600
 worker_thread+0xa63/0x1210 kernel/workqueue.c:2751
 kthread+0x2b8/0x350 kernel/kthread.c:389
 ret_from_fork+0x2e/0x60 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>
rcu: rcu_preempt kthread starved for 9926 jiffies! g94557 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:26568 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1873/0x48f0 kernel/sched/core.c:6710
 schedule+0xc3/0x180 kernel/sched/core.c:6786
 schedule_timeout+0x1bd/0x310 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x2c6/0x1010 kernel/rcu/tree.c:1609
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:1808
 kthread+0x2b8/0x350 kernel/kthread.c:389
 ret_from_fork+0x2e/0x60 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt+0x20/0x30 drivers/acpi/processor_idle.c:112