rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=53a/1/0x4000000000000002 softirq=12052/12052 fqs=0 
	(t=10500 jiffies g=6721 q=98)
rcu: rcu_preempt kthread starved for 10500 jiffies! g6721 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29032    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3385 [inline]
 __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
 schedule+0x181/0x210 kernel/sched/core.c:4155
 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
 rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 1
CPU: 1 PID: 8344 Comm: udevd Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fb/0x318 lib/dump_stack.c:118
 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
 rcu_pending kernel/rcu/tree.c:2827 [inline]
 rcu_sched_clock_irq+0xe25/0x1ad0 kernel/rcu/tree.c:2271
 update_process_times+0x12d/0x180 kernel/time/timer.c:1726
 tick_sched_handle kernel/time/tick-sched.c:167 [inline]
 tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
 __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:free_thread_stack+0x133/0x590 kernel/fork.c:280
Code: 00 ea ff ff 48 01 c7 be 03 00 00 00 e8 06 a2 60 00 e9 5d 04 00 00 e8 5c 2d 2e 00 48 89 df 31 f6 e8 42 af 6e 00 43 80 3c 2e 00 <74> 08 4c 89 e7 e8 43 a4 69 00 49 8b 1c 24 48 83 c3 08 48 89 d8 48
RSP: 0000:ffffc90002c57d40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000001 RBX: ffffea00024e3cc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea00024e3cc0
RBP: ffffc90002c57d78 R08: dffffc0000000000 R09: fffffbfff12877ed
R10: fffffbfff12877ed R11: 0000000000000000 R12: ffff888092b48020
R13: dffffc0000000000 R14: 1ffff11012569004 R15: ffff8880a78e7428
 release_task_stack kernel/fork.c:440 [inline]
 put_task_stack+0xa3/0x130 kernel/fork.c:451
 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
 schedule+0x181/0x210 kernel/sched/core.c:4155
 exit_to_usermode_loop arch/x86/entry/common.c:150 [inline]
 prepare_exit_to_usermode+0x2d4/0x5b0 arch/x86/entry/common.c:195
 ret_from_intr+0x26/0x36
RIP: 0033:0x7f015e903317
Code: 24 30 48 8b 40 08 48 89 44 24 70 48 8b 86 f8 02 00 00 48 85 c0 0f 84 fc 04 00 00 8b 96 f0 02 00 00 8b 8e f4 02 00 00 44 21 c2 <48> 8b 14 d0 4c 89 e8 48 d3 e8 48 89 c1 83 e1 3f 48 89 d0 48 d3 e8
RSP: 002b:00007ffd57853af0 EFLAGS: 00010202
RAX: 00007f015e1452c8 RBX: 00007f015eb11058 RCX: 000000000000000e
RDX: 000000000000007f RSI: 00007f015eb12000 RDI: 0000000000401790
RBP: 0000000000000003 R08: 0000000003f0b27f R09: 0000000000000005
R10: 0000000000000008 R11: 00007ffd57853b40 R12: 0000000000000007
R13: 00000000fc2c9fc5 R14: 0000000000000000 R15: 00007ffd57853cc8