rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=a22/1/0x4000000000000004 softirq=136921/136921 fqs=0 
	(t=10500 jiffies g=191265 q=123)
rcu: rcu_preempt kthread starved for 10500 jiffies! g191265 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     I28952    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3384 [inline]
 __schedule+0x74b/0xb80 kernel/sched/core.c:4069
 schedule+0x131/0x1e0 kernel/sched/core.c:4136
 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1639 [inline]
 rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1799
 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: 10419 Comm: syz-executor.4 Not tainted 5.4.0-rc3 #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+0x1d8/0x2f8 lib/dump_stack.c:113
 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:2795 [inline]
 rcu_sched_clock_irq+0xe22/0x1ae0 kernel/rcu/tree.c:2244
 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:1299
 __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:830
RIP: 0010:qdisc_root_sleeping include/net/sch_generic.h:504 [inline]
RIP: 0010:pie_timer+0x5d/0x7d0 net/sched/sch_pie.c:447
Code: 74 08 48 89 df e8 83 5a ab fb 4c 8b 3b 49 8d 5f 40 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 66 5a ab fb 48 8b 1b <48> 83 c3 10 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8
RSP: 0018:ffff8880aeb09cb0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff1100adba408 RBX: ffff888095345c00 RCX: ffff88804d3d8140
RDX: 0000000000000103 RSI: 0000000000000000 RDI: ffff888056dd2340
RBP: ffff8880aeb09d40 R08: ffffffff816362db R09: ffffed1015d66b05
R10: ffffed1015d66b05 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000103 R14: ffff888056dd2340 R15: ffff888056dd2000
 call_timer_fn+0x95/0x170 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers+0x7b6/0x990 kernel/time/timer.c:1773
 run_timer_softirq+0x4a/0x90 kernel/time/timer.c:1786
 __do_softirq+0x333/0x7c4 arch/x86/include/asm/paravirt.h:766
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x227/0x230 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x113/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 </IRQ>
RIP: 0010:debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline]
RIP: 0010:do_raw_spin_lock+0x3a/0x2d0 kernel/locking/spinlock_debug.c:112
Code: 30 49 89 fd 65 48 8b 04 25 28 00 00 00 48 89 45 d0 49 be 00 00 00 00 00 fc ff df 48 8d 5f 04 48 89 d8 48 c1 e8 03 42 8a 04 30 <84> c0 0f 85 9e 01 00 00 81 3b ad 4e ad de 0f 85 b6 01 00 00 49 8d
RSP: 0018:ffff888046d67c18 EFLAGS: 00000a07 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff1121100 RBX: ffffffff88908e7c RCX: ffffffff81594302
RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffffffff88908e78
RBP: ffff888046d67c70 R08: dffffc0000000000 R09: fffffbfff12bb69e
R10: fffffbfff12bb69e R11: 0000000000000000 R12: ffff8880a5358040
R13: ffffffff88908e78 R14: dffffc0000000000 R15: ffff888046d67ea8
 __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_lock+0x39/0x40 kernel/locking/spinlock.c:151
 spin_lock include/linux/spinlock.h:338 [inline]
 chroot_fs_refs+0xf3/0x4e0 fs/fs_struct.c:70
 __do_sys_pivot_root fs/namespace.c:3700 [inline]
 __se_sys_pivot_root+0x1d85/0x1eb0 fs/namespace.c:3617
 __x64_sys_pivot_root+0x5b/0x70 fs/namespace.c:3617
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe9c4fddc78 EFLAGS: 00000246 ORIG_RAX: 000000000000009b
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000459a59
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000020000200
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe9c4fde6d4
R13: 00000000004c6b47 R14: 00000000004dc138 R15: 00000000ffffffff