rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=756/1/0x4000000000000002 softirq=13249/13249 fqs=39 
	(t=10501 jiffies g=6973 q=856)
rcu: rcu_preempt kthread starved for 10421 jiffies! g6973 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    28984    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 1
CPU: 1 PID: 8651 Comm: syz-executor.0 Not tainted 5.5.0-rc5-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: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+0x18b/0x590 kernel/fork.c:284
Code: ff ff e8 28 04 00 00 43 80 3c 2e 00 74 08 4c 89 e7 e8 39 94 6a 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 1b 94 6a 00 48 8b 1b e9 82 ff ff ff e8 be 2b 2e
RSP: 0018:ffffc90002787e40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11012f11df1 RBX: ffff88809788ef88 RCX: ffff88808fa58040
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea0002608b00
RBP: ffffc90002787e78 R08: 000000000003a728 R09: ffffed1012e78729
R10: ffffed1012e78729 R11: 0000000000000000 R12: ffff888094250020
R13: dffffc0000000000 R14: 1ffff1101284a004 R15: ffff8880973c3938
 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
 schedule_tail+0x20/0x1a0 kernel/sched/core.c:3320
 ret_from_fork+0x8/0x30 arch/x86/entry/entry_64.S:336
RIP: 0033:0x45d919
Code: ff 48 85 f6 0f 84 d7 8c fb ff 48 83 ee 10 48 89 4e 08 48 89 3e 48 89 d7 4c 89 c2 4d 89 c8 4c 8b 54 24 08 b8 38 00 00 00 0f 05 <48> 85 c0 0f 8c ae 8c fb ff 74 01 c3 31 ed 48 f7 c7 00 00 01 00 75
RSP: 002b:00007f3d2546fdb0 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: 0000000000000000 RBX: 00007f3d25470700 RCX: 000000000045d919
RDX: 00007f3d254709d0 RSI: 00007f3d2546fdb0 RDI: 00000000003d0f00
RBP: 00007ffd26a9b0a0 R08: 00007f3d25470700 R09: 00007f3d25470700
R10: 00007f3d254709d0 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffd26a9af3f R14: 00007f3d254709c0 R15: 000000000075bf2c