rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4161/1:b..l
	(detected by 0, t=10502 jiffies, g=11481, q=548 ncpus=2)
task:syz.3.99        state:R  running task     stack:24984 pid:4161  ppid:3827   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6873
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:653
RIP: 0010:__rcu_read_unlock+0x7/0x100 kernel/rcu/tree_plugin.h:419
Code: 89 f9 80 e1 07 80 c1 03 38 c1 7c b0 4c 89 ff e8 9f 03 6e 00 eb a6 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 55 41 57 41 56 41 55 <41> 54 53 49 bc 00 00 00 00 00 fc ff df 65 4c 8b 35 44 4f 8e 7e 4d
RSP: 0018:ffffc900047a79f8 EFLAGS: 00000246
RAX: ffffffff8921fe22 RBX: ffffffff8921f62f RCX: 0000000000040000
RDX: ffffc900160a7000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: ffffc900047a7b50 R08: ffffffff8921fe10 R09: fffffbfff20e7245
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff920008f4f5e
R13: dffffc0000000000 R14: ffffc900013b9c30 R15: ffffffff92370c20
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 inet_twsk_purge+0x96d/0xa40 net/ipv4/inet_timewait_sock.c:336
 tcp_twsk_purge+0xd6/0x140 net/ipv4/tcp_minisocks.c:360
 ops_exit_list net/core/net_namespace.c:177 [inline]
 setup_net+0x939/0xb90 net/core/net_namespace.c:358
 copy_net_ns+0x392/0x5d0 net/core/net_namespace.c:481
 create_new_namespaces+0x425/0x7a0 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11e/0x170 kernel/nsproxy.c:226
 ksys_unshare+0x580/0xb20 kernel/fork.c:3203
 __do_sys_unshare kernel/fork.c:3274 [inline]
 __se_sys_unshare kernel/fork.c:3272 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3272
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4552d773b9
RSP: 002b:00007f4553a95048 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f4552f06058 RCX: 00007f4552d773b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000006a040000
RBP: 00007f4552de48e6 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f4552f06058 R15: 00007ffd62e87988
 </TASK>
rcu: rcu_preempt kthread starved for 9552 jiffies! g11481 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:27064 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 schedule+0xbf/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </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:111 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:567