syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (1 ticks this GP) idle=f06/1/0x4000000000000002 softirq=106661/106661 fqs=0 
	(t=27807 jiffies g=124605 q=20197)
rcu: rcu_preempt kthread starved for 27807 jiffies! g124605 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29128    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_timeout+0x486/0xc50 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1658 [inline]
 rcu_gp_kthread+0xa10/0x1940 kernel/rcu/tree.c:1818
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 0
CPU: 0 PID: 11004 Comm: kworker/0:6 Not tainted 5.6.0-rc3-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+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:475 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:549 [inline]
 rcu_pending kernel/rcu/tree.c:3030 [inline]
 rcu_sched_clock_irq.cold+0x51a/0xc37 kernel/rcu/tree.c:2276
 update_process_times+0x2d/0x70 kernel/time/timer.c:1726
 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:171
 tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1314
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline]
 smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1144
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:preempt_schedule_irq+0xab/0x160 kernel/sched/core.c:4337
Code: 00 00 e8 78 84 61 f9 e8 03 bc 8b f9 4c 89 f0 48 c1 e8 03 80 3c 18 00 75 7d 48 83 3d 96 4b c4 01 00 74 6f fb 66 0f 1f 44 00 00 <bf> 01 00 00 00 e8 ab d1 ff ff 48 c7 c0 00 b1 b3 89 48 c1 e8 03 80
RSP: 0018:ffffc90001857af8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff1367621 RBX: dffffc0000000000 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8880a71c0b14
RBP: ffffc90001857b18 R08: 1ffffffff16a3571 R09: fffffbfff16a3572
R10: fffffbfff16a3571 R11: ffffffff8b51ab8f R12: ffffed1014e38050
R13: ffff8880a71c0280 R14: ffffffff89b3b108 R15: 0000000000000000
 retint_kernel+0x1b/0x2b
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:queue_delayed_work_on+0x12a/0x210 kernel/workqueue.c:1673
Code: 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 d8 00 00 00 48 83 3d 5e 2f 66 08 00 0f 84 9a 00 00 00 e8 ab 05 28 00 48 89 df 57 9d <0f> 1f 44 00 00 e8 9c 05 28 00 44 89 f8 48 83 c4 10 5b 41 5c 41 5d
RSP: 0018:ffffc90001857bd0 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff02
RAX: ffff8880a71c0280 RBX: 0000000000000293 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffffffff814d81a5 RDI: 0000000000000293
RBP: ffffc90001857c08 R08: 1ffffffff16a3571 R09: fffffbfff16a3572
R10: fffffbfff16a3571 R11: ffffffff8b51ab8f R12: 0000000000000200
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
 queue_delayed_work include/linux/workqueue.h:509 [inline]
 srcu_reschedule kernel/rcu/srcutree.c:1226 [inline]
 srcu_reschedule+0xd7/0x130 kernel/rcu/srcutree.c:1209
 process_srcu+0x125/0xe10 kernel/rcu/srcutree.c:1239
 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264
 worker_thread+0x98/0xe40 kernel/workqueue.c:2410
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352