syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 GPs behind) idle=d9a/1/0x4000000000000002 softirq=28696/28697 fqs=0 
rcu: 	 (t=11073 jiffies g=35957 q=117)
NMI backtrace for cpu 1
CPU: 1 PID: 7827 Comm: syz-fuzzer Not tainted 4.20.0-rc7-next-20181224 #190
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+0x1d3/0x2c6 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.4+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1c2/0x22c 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+0x16f/0x1bc kernel/rcu/tree.c:1211
 print_cpu_stall.cold.70+0x218/0x40a kernel/rcu/tree.c:1348
 check_cpu_stall kernel/rcu/tree.c:1422 [inline]
 rcu_pending kernel/rcu/tree.c:3018 [inline]
 rcu_check_callbacks+0xac1/0x1410 kernel/rcu/tree.c:2521
 update_process_times+0x2d/0x70 kernel/time/timer.c:1635
 tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:161
 tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1271
 __run_hrtimer kernel/time/hrtimer.c:1389 [inline]
 __hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1451
 hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1509
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
 smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1060
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x56/0x80 kernel/locking/spinlock.c:192
Code: 72 89 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 32 48 83 3d 23 d2 77 01 00 74 1f fb 66 0f 1f 44 00 00 <bf> 01 00 00 00 e8 10 83 5d f9 65 8b 05 99 75 07 78 85 c0 74 05 5b
RSP: 0018:ffff88808fd1f0d8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: ffff8880ae72ce00 RCX: 0000000000000000
RDX: 1ffffffff12e4948 RSI: 0000000000000001 RDI: ffffffff89724a40
RBP: ffff88808fd1f0e0 R08: ffff8880856ca280 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880856ca280
R13: ffff8880a9460340 R14: ffff88809bf80500 R15: dffffc0000000000
 finish_lock_switch kernel/sched/core.c:2581 [inline]
 finish_task_switch+0x1f4/0x910 kernel/sched/core.c:2681
 context_switch kernel/sched/core.c:2834 [inline]
 __schedule+0x9e6/0x1ed0 kernel/sched/core.c:3472
 schedule+0xef/0x370 kernel/sched/core.c:3516
 freezable_schedule include/linux/freezer.h:172 [inline]
 futex_wait_queue_me+0x3f9/0x840 kernel/futex.c:2590
 futex_wait+0x45c/0xa50 kernel/futex.c:2705
 do_futex+0x31a/0x26d0 kernel/futex.c:3588
 __do_sys_futex kernel/futex.c:3649 [inline]
 __se_sys_futex kernel/futex.c:3617 [inline]
 __x64_sys_futex+0x469/0x690 kernel/futex.c:3617
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45ddf3
Code: cc cc cc cc cc cc cc 48 8b 7c 24 08 8b 74 24 10 8b 54 24 14 4c 8b 54 24 18 4c 8b 44 24 20 44 8b 4c 24 28 b8 ca 00 00 00 0f 05 <89> 44 24 30 c3 cc cc cc cc cc cc cc cc 8b 7c 24 08 48 8b 74 24 10
RSP: 002b:000000c420035e80 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045ddf3
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000015e4558
RBP: 000000c420035ec8 R08: 0000000000000000 R09: 0000000000000000
R10: 000000c420035eb8 R11: 0000000000000246 R12: 0000000000430120
R13: 00000000000000f1 R14: 0000000000000011 R15: 0000000000000000