INFO: rcu detected stall in fuse_put_super

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 1236568ee3cb Merge tag 'gpio-v4.18-3' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=127d4bb4400000
kernel config: https://syzkaller.appspot.com/x/.config?x=152cb8ccd35b1f70
dashboard link: https://syzkaller.appspot.com/bug?extid=66df86c7e661f13f24c9
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
mik...@szeredi.hu]

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+66df86...@syzkaller.appspotmail.com

INFO: rcu_sched detected stalls on CPUs/tasks:
(detected by 0, t=105007 jiffies, g=54385, c=54384, q=120)
All QSes seen, last rcu_sched kthread activity 105014
(4295063628-4294958614), jiffies_till_next_fqs=3, root ->qsmask 0x0
syz-executor5 R running task 25224 22239 4482 0x00000008
Call Trace:
<IRQ>
sched_show_task.cold.84+0x27a/0x301 kernel/sched/core.c:5324
print_other_cpu_stall.cold.77+0x92f/0x9d2 kernel/rcu/tree.c:1441
check_cpu_stall.isra.60+0x721/0xf70 kernel/rcu/tree.c:1559
__rcu_pending kernel/rcu/tree.c:3244 [inline]
rcu_pending kernel/rcu/tree.c:3291 [inline]
rcu_check_callbacks+0x23f/0xcd0 kernel/rcu/tree.c:2646
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:863
</IRQ>
RIP: 0010:clear_bit arch/x86/include/asm/bitops.h:114 [inline]
RIP: 0010:fuse_abort_conn+0xb1f/0x1580 fs/fuse/dev.c:2122
Code: 80 fd ff ff 4c 8b ad 68 fc ff ff 48 bb 00 00 00 00 00 fc ff df 4c 3b
a5 68 fc ff ff 74 26 e8 38 24 14 ff f0 41 80 64 24 30 7f <4c> 89 e0 48 c1
e8 03 80 3c 18 00 0f 85 80 05 00 00 4d 8b 24 24 4d
RSP: 0018:ffff880198357618 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000040000 RBX: dffffc0000000000 RCX: ffffc9000d4c7000
RDX: 0000000000040000 RSI: ffffffff8267f418 RDI: ffff8801d7f27270
RBP: ffff8801983579e0 R08: ffffed003afe4e50 R09: ffffed003afe4e4f
R10: ffffed003afe4e4f R11: ffff8801d7f2727b R12: ffff8801ae944108
R13: ffff880198357738 R14: ffff8801983579b8 R15: dffffc0000000000
fuse_put_super+0x123/0x440 fs/fuse/inode.c:396
generic_shutdown_super+0x1bf/0x530 fs/super.c:453
kill_anon_super+0x3c/0x50 fs/super.c:1046
fuse_kill_sb_anon+0x90/0xb0 fs/fuse/inode.c:1223
deactivate_locked_super+0x97/0x100 fs/super.c:326
deactivate_super+0x193/0x1c0 fs/super.c:357
cleanup_mnt+0xbf/0x160 fs/namespace.c:1174
__cleanup_mnt+0x16/0x20 fs/namespace.c:1181
task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:192 [inline]
exit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x456cb9
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fc8f9ed9c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fc8f9eda6d4 RCX: 0000000000456cb9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000100
RBP: 0000000000930280 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d6360 R14: 00000000004c9ab8 R15: 0000000000000003
rcu_sched kthread starved for 105703 jiffies! g54385 c54384 f0x2
RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
RCU grace-period kthread stack dump:
rcu_sched R running task 23688 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2853 [inline]
__schedule+0x87c/0x1ec0 kernel/sched/core.c:3501
schedule+0xfb/0x450 kernel/sched/core.c:3545
schedule_timeout+0x140/0x260 kernel/time/timer.c:1801
rcu_gp_kthread+0x717/0x1c90 kernel/rcu/tree.c:2179
kthread+0x345/0x410 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412


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[syzbot]

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