rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=79a/1/0x4000000000000000 softirq=41494/41495 fqs=1209 
	(t=10502 jiffies g=72297 q=865)
NMI backtrace for cpu 1
CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.14.0-rc6-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:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x25e/0x3f0 kernel/rcu/tree_stall.h:342
 print_cpu_stall kernel/rcu/tree_stall.h:625 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:700 [inline]
 rcu_pending kernel/rcu/tree.c:3922 [inline]
 rcu_sched_clock_irq.cold+0x9f/0x747 kernel/rcu/tree.c:2641
 update_process_times+0x16d/0x200 kernel/time/timer.c:1785
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226
 tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1421
 __run_hrtimer kernel/time/hrtimer.c:1537 [inline]
 __hrtimer_run_queues+0x1c0/0xe50 kernel/time/hrtimer.c:1601
 hrtimer_interrupt+0x330/0xa00 kernel/time/hrtimer.c:1663
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1089 [inline]
 __sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1106
 sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1100
 </IRQ>
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:191
Code: 74 24 10 e8 0a fa 2d f8 48 89 ef e8 b2 6f 2e f8 81 e3 00 02 00 00 75 25 9c 58 f6 c4 02 75 2d 48 85 db 74 01 fb bf 01 00 00 00 <e8> 73 4d 22 f8 65 8b 05 5c c8 d4 76 85 c0 74 0a 5b 5d c3 e8 c0 a9
RSP: 0018:ffffc90000d979f0 EFLAGS: 00000206
RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff1fa904a
RDX: 0000000000000000 RSI: 0000000000000101 RDI: 0000000000000001
RBP: ffff888146754000 R08: 0000000000000001 R09: ffffffff8fcd4a17
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88801dc0d008
R13: ffff88801b7d2600 R14: dffffc0000000000 R15: ffff88801dc0d000
 spin_unlock_irqrestore include/linux/spinlock.h:409 [inline]
 dummy_timer+0x12f6/0x32b0 drivers/usb/gadget/udc/dummy_hcd.c:2001
 call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1421
 expire_timers kernel/time/timer.c:1466 [inline]
 __run_timers.part.0+0x675/0xa20 kernel/time/timer.c:1734
 __run_timers kernel/time/timer.c:1715 [inline]
 run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1747
 __do_softirq+0x29b/0x9c2 kernel/softirq.c:558
 run_ksoftirqd kernel/softirq.c:920 [inline]
 run_ksoftirqd+0x2d/0x60 kernel/softirq.c:912
 smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
 kthread+0x3e5/0x4d0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
----------------
Code disassembly (best guess):
   0:	74 24                	je     0x26
   2:	10 e8                	adc    %ch,%al
   4:	0a fa                	or     %dl,%bh
   6:	2d f8 48 89 ef       	sub    $0xef8948f8,%eax
   b:	e8 b2 6f 2e f8       	callq  0xf82e6fc2
  10:	81 e3 00 02 00 00    	and    $0x200,%ebx
  16:	75 25                	jne    0x3d
  18:	9c                   	pushfq 
  19:	58                   	pop    %rax
  1a:	f6 c4 02             	test   $0x2,%ah
  1d:	75 2d                	jne    0x4c
  1f:	48 85 db             	test   %rbx,%rbx
  22:	74 01                	je     0x25
  24:	fb                   	sti    
  25:	bf 01 00 00 00       	mov    $0x1,%edi
  2a:	e8 73 4d 22 f8       	callq  0xf8224da2 <-- trapping instruction
  2f:	65 8b 05 5c c8 d4 76 	mov    %gs:0x76d4c85c(%rip),%eax        # 0x76d4c892
  36:	85 c0                	test   %eax,%eax
  38:	74 0a                	je     0x44
  3a:	5b                   	pop    %rbx
  3b:	5d                   	pop    %rbp
  3c:	c3                   	retq   
  3d:	e8                   	.byte 0xe8
  3e:	c0                   	.byte 0xc0
  3f:	a9                   	.byte 0xa9