rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10499 ticks this GP) idle=22a/1/0x4000000000000002 softirq=9851/9851 fqs=23 
	(t=10501 jiffies g=6341 q=505)
rcu: rcu_preempt kthread starved for 10455 jiffies! g6341 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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 0
CPU: 0 PID: 4169 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:check_kcov_mode kernel/kcov.c:68 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x14/0x50 kernel/kcov.c:102
Code: 00 00 00 48 8b 3d 74 25 cd 07 48 89 de e8 64 02 3b 00 5b 5d c3 cc 48 8b 04 24 65 48 8b 0c 25 c0 1d 02 00 65 8b 15 b8 81 8b 7e <f7> c2 00 01 1f 00 75 2c 8b 91 80 13 00 00 83 fa 02 75 21 48 8b 91
RSP: 0018:ffffc9000200fad8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffffffff81487433 RBX: 0000000000000000 RCX: ffff8880a03fe1c0
RDX: 0000000000000001 RSI: 00000000fffffffc RDI: ffffea00028b0140
RBP: ffffc9000200fb00 R08: dffffc0000000000 R09: fffffbfff120248a
R10: fffffbfff120248a R11: 0000000000000000 R12: dffffc0000000000
R13: dffffc0000000000 R14: 00000000fffffffc R15: ffff88809939b728
 free_thread_stack+0x168/0x590 kernel/fork.c:280
 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
 schedule_hrtimeout_range_clock+0x3c7/0x510 kernel/time/hrtimer.c:2127
 schedule_hrtimeout_range+0x2a/0x40 kernel/time/hrtimer.c:2172
 ep_poll+0xa4d/0xe80 fs/eventpoll.c:1915
 do_epoll_wait+0x1ee/0x260 fs/eventpoll.c:2294
 __do_sys_epoll_wait fs/eventpoll.c:2304 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2301 [inline]
 __x64_sys_epoll_wait+0x9a/0xb0 fs/eventpoll.c:2301
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fd9daeee943
Code: 00 31 d2 48 29 c2 64 89 11 48 83 c8 ff eb ea 90 90 90 90 90 90 90 90 83 3d b5 dc 2a 00 00 75 13 49 89 ca b8 e8 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 3b c4 00 00 48 89 04 24
RSP: 002b:00007ffec7ed6048 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8
RAX: ffffffffffffffda RBX: 0000000001446250 RCX: 00007fd9daeee943
RDX: 0000000000000004 RSI: 00007ffec7ed6110 RDI: 0000000000000007
RBP: 0000000000625500 R08: 00007ffec7ed6030 R09: 00007ffec7f440b8
R10: 000000000000ee42 R11: 0000000000000246 R12: 000000000145f530
R13: 00007ffec7ed7167 R14: 0000000000000005 R15: 0000000001446250