rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 ticks this GP) idle=cf6/1/0x4000000000000002 softirq=16916/16916 fqs=0 
	(t=11131 jiffies g=19561 q=196)
rcu: rcu_preempt kthread starved for 11131 jiffies! g19561 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     I29120    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3254 [inline]
 __schedule+0x755/0x15b0 kernel/sched/core.c:3921
 schedule+0xa8/0x270 kernel/sched/core.c:3985
 schedule_timeout+0x486/0xc50 kernel/time/timer.c:1893
 rcu_gp_fqs_loop kernel/rcu/tree.c:1611 [inline]
 rcu_gp_kthread+0x9b2/0x18c0 kernel/rcu/tree.c:1768
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 1
CPU: 1 PID: 9858 Comm: syz-fuzzer Not tainted 5.3.0-rc2-next-20190802 #58
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+0x172/0x1f0 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x183/0x1cf 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:2736 [inline]
 rcu_sched_clock_irq.cold+0x4dd/0xc13 kernel/rcu/tree.c:2183
 update_process_times+0x32/0x80 kernel/time/timer.c:1724
 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:167
 tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1299
 __run_hrtimer kernel/time/hrtimer.c:1493 [inline]
 __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1555
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1617
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1068 [inline]
 smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1093
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:828
 </IRQ>
RIP: 0010:do_user_addr_fault arch/x86/mm/fault.c:1339 [inline]
RIP: 0010:__do_page_fault+0x842/0xdd0 arch/x86/mm/fault.c:1506
Code: ff df 48 c1 e8 03 80 3c 10 00 0f 85 ab 04 00 00 48 83 3d 30 a4 a0 07 00 0f 84 8f 03 00 00 e8 35 d3 3f 00 fb 66 0f 1f 44 00 00 <c7> 45 c0 54 00 00 00 e9 4e fa ff ff e8 1d d3 3f 00 48 8b 45 c8 48
RSP: 0000:ffff8880a2167ea0 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
RAX: ffff888095fb0240 RBX: 000000c42ae78000 RCX: 1ffffffff134c076
RDX: 0000000000000000 RSI: ffffffff8132508b RDI: ffffffff81325059
RBP: ffff8880a2167f10 R08: ffff888095fb0240 R09: 0000000000000000
R10: ffffed101442cfff R11: ffff8880a2167fff R12: 000000c42ae78010
R13: 0000000000000006 R14: ffff8880a2167f58 R15: ffff8880a2167fe0
 do_page_fault+0x38/0x590 arch/x86/mm/fault.c:1530
 page_fault+0x39/0x40 arch/x86/entry/entry_64.S:1200
RIP: 0033:0x420ac8
Code: 74 63 31 c9 eb 06 48 89 d1 48 89 f0 48 8d 91 00 08 00 00 48 81 fa 00 80 00 00 77 3a 48 8b 5c 24 18 48 8b 73 18 48 01 ce 84 03 <48> c7 46 10 00 00 00 00 48 85 c9 74 cf 48 89 54 24 10 48 89 44 24
RSP: 002b:000000c420127d40 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007f968ed67be8 RCX: 0000000000000000
RDX: 0000000000000800 RSI: 000000c42ae78000 RDI: 000000000000a800
RBP: 000000c420127d88 R08: 000000c000000000 R09: 000000000000573f
R10: 0000000000000004 R11: 0000000000000246 R12: 01ffffffffffffff
R13: 0000000000000003 R14: 00000000000000df R15: 0000000000000000