INFO: rcu detected stall in finish_task_switch

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 116b181bb646 Add linux-next specific files for 20180803
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12927272400000
kernel config: https://syzkaller.appspot.com/x/.config?x=b4f38be7c2c519d5
dashboard link: https://syzkaller.appspot.com/bug?extid=30b213ce827f4e0a9e11
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [dvh...@infradead.org linux-...@vger.kernel.org
mi...@redhat.com pet...@infradead.org tg...@linutronix.de]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+30b213...@syzkaller.appspotmail.com

rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 1-...!: (1 ticks this GP) idle=2e6/1/0x4000000000000002
softirq=21091/21091 fqs=0
rcu: (t=110325 jiffies g=45621 q=219)
rcu: rcu_sched kthread starved for 110325 jiffies! g45621 f0x0
RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_sched I23480 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2823 [inline]
__schedule+0x87c/0x1ec0 kernel/sched/core.c:3471
schedule+0xfb/0x450 kernel/sched/core.c:3515
schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
rcu_gp_kthread+0x743/0x1d20 kernel/rcu/tree.c:2194
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
NMI backtrace for cpu 1
CPU: 1 PID: 4356 Comm: syz-fuzzer Not tainted 4.18.0-rc7-next-20180803+ #31
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+0x1c9/0x2b4 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.3+0x48/0x88 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x151/0x192 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:162 [inline]
rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340
print_cpu_stall.cold.78+0x2fb/0x59c kernel/rcu/tree.c:1478
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3276 [inline]
rcu_pending kernel/rcu/tree.c:3319 [inline]
rcu_check_callbacks+0xd93/0x1660 kernel/rcu/tree.c:2665
update_process_times+0x2d/0x70 kernel/time/timer.c:1636
tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x3eb/0x10c0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1028 [inline]
smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1053
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
</IRQ>
RIP: 0010:arch_local_irq_enable arch/x86/include/asm/paravirt.h:793 [inline]
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:168
[inline]
RIP: 0010:_raw_spin_unlock_irq+0x56/0x70 kernel/locking/spinlock.c:192
Code: f1 87 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00
75 1d 48 83 3d 6b 41 39 01 00 74 11 fb 66 0f 1f 44 00 00 <65> ff 0d 33 7e
49 79 5b 5d c3 0f 0b e8 59 2a 03 fb eb dc 0f 1f 80
RSP: 0018:ffff8801ad6ef090 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: ffff8801db12ca40 RCX: ffffffff81606487
RDX: 1ffffffff0fe361f RSI: 0000000000000004 RDI: ffffffff87f1b0f8
RBP: ffff8801ad6ef098 R08: ffffed003b625949 R09: ffffed003b625948
R10: ffffed003b625948 R11: ffff8801db12ca43 R12: ffff8801ad502180
R13: ffff8801d9f18380 R14: ffff88019c2e98c0 R15: dffffc0000000000
finish_lock_switch kernel/sched/core.c:2575 [inline]
finish_task_switch+0x1d3/0x870 kernel/sched/core.c:2675
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x884/0x1ec0 kernel/sched/core.c:3471
schedule+0xfb/0x450 kernel/sched/core.c:3515
freezable_schedule include/linux/freezer.h:172 [inline]
futex_wait_queue_me+0x3f9/0x840 kernel/futex.c:2530
futex_wait+0x45b/0xa20 kernel/futex.c:2645
do_futex+0x336/0x27d0 kernel/futex.c:3527
__do_sys_futex kernel/futex.c:3587 [inline]
__se_sys_futex kernel/futex.c:3555 [inline]
__x64_sys_futex+0x472/0x6a0 kernel/futex.c:3555
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: 0000000001448298
RBP: 000000c420035ec8 R08: 0000000000000000 R09: 0000000000000000
R10: 000000c420035eb8 R11: 0000000000000246 R12: 0000000000430130
R13: 00000000000000f1 R14: 0000000000000011 R15: 0000000000000000


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.