rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10499 ticks this GP) idle=e3a/1/0x4000000000000002 softirq=11493/11493 fqs=4 
	(t=10500 jiffies g=6477 q=94)
rcu: rcu_preempt kthread starved for 10492 jiffies! g6477 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: 5 Comm: kworker/0:0 Not tainted 5.4.0-syzkaller #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+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:1517 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1641
 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+0x14c/0x590 kernel/fork.c:280
Code: 2e 00 48 89 df 31 f6 e8 a2 a1 6e 00 43 80 3c 2e 00 74 08 4c 89 e7 e8 43 a0 69 00 49 8b 1c 24 48 83 c3 08 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 25 a0 69 00 48 8b 3b be fc ff ff
RSP: 0018:ffffc90000cbf8f8 EFLAGS: 00000a06 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11012788a71 RBX: ffff888093c45388 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea00028d9540
RBP: ffffc90000cbf930 R08: 000000000003a728 R09: fffffbfff120248a
R10: fffffbfff120248a R11: 0000000000000000 R12: ffff888093c45420
R13: dffffc0000000000 R14: 1ffff11012788a84 R15: ffff88808d3db528
 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
 preempt_schedule_irq+0xc1/0x140 kernel/sched/core.c:4338
 retint_kernel+0x1b/0x2b
RIP: 0010:delay_tsc+0x96/0xf0 arch/x86/lib/delay.c:68
Code: fb 41 89 c7 0f 01 f9 66 90 49 89 d4 49 c1 e4 20 49 09 c4 eb 29 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 a8 01 75 ca f3 90 <bf> 01 00 00 00 e8 d0 ea 62 f9 e8 4b b4 a3 fb 41 39 c7 75 bb 0f 01
RSP: 0018:ffffc90000cbfb48 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000080000000 RBX: 0000000000001fee RCX: 0000000000000001
RDX: 0000000000000023 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffc90000cbfb68 R08: ffffffff8393cb27 R09: fffffbfff14572fd
R10: fffffbfff14572fd R11: 0000000000000000 R12: 00000023818af5df
R13: 0000000000000000 R14: 0000000000002ced R15: 0000000000000000
 __delay arch/x86/lib/delay.c:161 [inline]
 __const_udelay+0x5e/0x70 arch/x86/lib/delay.c:175
 try_check_zero+0x6e/0x380 kernel/rcu/srcutree.c:705
 srcu_advance_state kernel/rcu/srcutree.c:1142 [inline]
 process_srcu+0x1b7/0xd20 kernel/rcu/srcutree.c:1237
 process_one_work+0x7ef/0x10d0 kernel/workqueue.c:2264
 worker_thread+0xc01/0x1630 kernel/workqueue.c:2410
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352