rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 ticks this GP) idle=8d6/1/0x4000000000000004 softirq=110347/110347 fqs=0 
	(t=30001 jiffies g=148133 q=340)
rcu: rcu_preempt kthread starved for 30001 jiffies! g148133 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     I29040    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3384 [inline]
 __schedule+0x94f/0x1e70 kernel/sched/core.c:4069
 schedule+0xd9/0x260 kernel/sched/core.c:4136
 schedule_timeout+0x486/0xc50 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1639 [inline]
 rcu_gp_kthread+0x9b2/0x18d0 kernel/rcu/tree.c:1799
 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: 1945 Comm: kworker/1:0 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: rcu_gp process_srcu
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 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:2795 [inline]
 rcu_sched_clock_irq.cold+0x4fd/0xc12 kernel/rcu/tree.c:2244
 update_process_times+0x2d/0x70 kernel/time/timer.c:1726
 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:1514 [inline]
 __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
RIP: 0010:ffs arch/x86/include/asm/bitops.h:297 [inline]
RIP: 0010:__do_softirq+0x227/0x98c kernel/softirq.c:280
Code: c7 c0 f0 1d f3 88 48 c1 e8 03 42 80 3c 30 00 0f 85 b1 06 00 00 48 83 3d d6 1b 73 01 00 0f 84 d6 05 00 00 fb 66 0f 1f 44 00 00 <b8> ff ff ff ff 48 c7 45 c8 00 91 e0 88 0f bc 45 d4 83 c0 01 89 45
RSP: 0018:ffff8880ae909f20 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11e63be RBX: ffff88805ec3e140 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88805ec3e9d4
RBP: ffff8880ae909fa0 R08: 1ffffffff14efd39 R09: fffffbfff14efd3a
R10: fffffbfff14efd39 R11: ffffffff8a77e9cf R12: 0000000000000028
R13: 0000000000000028 R14: dffffc0000000000 R15: 0000000000000000
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x19b/0x1e0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 do_IRQ+0xe3/0x280 arch/x86/kernel/irq.c:263
 common_interrupt+0xf/0xf arch/x86/entry/entry_64.S:607
 </IRQ>
RIP: 0010:preempt_count_add+0x22/0x160 kernel/sched/core.c:3778
Code: 0f 1f 84 00 00 00 00 00 48 c7 c0 a0 c1 ae 8a 55 48 ba 00 00 00 00 00 fc ff df 48 89 c1 48 89 e5 41 54 83 e0 07 48 c1 e9 03 53 <83> c0 03 89 fb 0f b6 14 11 38 d0 7c 08 84 d2 0f 85 00 01 00 00 8b
RSP: 0018:ffff8880974cfb90 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffffd7
RAX: 0000000000000000 RBX: 0000029935a0a426 RCX: 1ffffffff155d834
RDX: dffffc0000000000 RSI: ffffffff834736bc RDI: 0000000000000001
RBP: ffff8880974cfba0 R08: ffff88805ec3e140 R09: 0000000000000040
R10: 0000000000000040 R11: ffffffff89052ac7 R12: 0000029935a09af8
R13: 0000000000000001 R14: 0000000000002ced R15: 00000000000033c3
 delay_tsc+0x3d/0xc0 arch/x86/lib/delay.c:68
 __delay arch/x86/lib/delay.c:161 [inline]
 __const_udelay+0x59/0x80 arch/x86/lib/delay.c:175
 try_check_zero+0x201/0x330 kernel/rcu/srcutree.c:705
 srcu_advance_state kernel/rcu/srcutree.c:1142 [inline]
 process_srcu+0x329/0xe10 kernel/rcu/srcutree.c:1237
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352