INFO: task syz-executor.3:2135 blocked for more than 140 seconds.
      Not tainted 4.9.155+ #27
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D25016  2135      1 0x00000004
 ffff8801ce162f80 ffff8801a3463c80 ffff8801db721000 ffff88019fa0c740
 ffff8801db721018 ffff8801a782f598 ffffffff82806806 e527cbc32534c555
 0000000000000001 ffff8801ce163830 0000000000000006 ffff8801db7218f0
Call Trace:
 [<ffffffff82807d92>] schedule+0x92/0x1c0 kernel/sched/core.c:3553
 [<ffffffff82808733>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff8280a68d>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8280a68d>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<ffffffff818928ad>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364
 [<ffffffff81873bb9>] fuse_lookup+0x89/0x3b0 fs/fuse/dir.c:406
 [<ffffffff8152c99b>] lookup_slow+0x24b/0x480 fs/namei.c:1709
 [<ffffffff8153bc0e>] walk_component+0x71e/0xce0 fs/namei.c:1825
 [<ffffffff8153ca67>] link_path_walk+0x897/0x1200 fs/namei.c:2161
 [<ffffffff8153d977>] path_mountpoint+0x67/0x6d0 fs/namei.c:2737
 [<ffffffff8154238f>] filename_mountpoint+0x17f/0x350 fs/namei.c:2758
 [<ffffffff81543a8a>] user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2788
 [<ffffffff81579bd6>] SYSC_umount fs/namespace.c:1722 [inline]
 [<ffffffff81579bd6>] SyS_umount+0x136/0xd30 fs/namespace.c:1706
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff82816a93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbab>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbab>] watchdog+0x11b/0xa40 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813fea8f>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/1908:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff8156f2f8>] __fdget_pos+0xa8/0xd0 fs/file.c:781
2 locks held by getty/2035:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82814b83>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d3982e>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.3/2135:
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<ffffffff8152c8b0>] inode_lock_shared include/linux/fs.h:778 [inline]
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<ffffffff8152c8b0>] lookup_slow+0x160/0x480 fs/namei.c:1686
 #1:  (&fi->mutex){+.+.+.}, at: [<ffffffff818928ad>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364
2 locks held by syz-executor.3/16297:
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<ffffffff8152c8b0>] inode_lock_shared include/linux/fs.h:778 [inline]
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<ffffffff8152c8b0>] lookup_slow+0x160/0x480 fs/namei.c:1686
 #1:  (&fi->mutex){+.+.+.}, at: [<ffffffff818928ad>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.155+ #27
 ffff8801d9907cd0 ffffffff81b47871 0000000000000000 0000000000000000
 0000000000000000 ffffffff81097301 00000000003fff9a ffff8801d9907d08
 ffffffff81b52afc 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b47871>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81b52afc>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b52a84>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<ffffffff81097494>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131c087>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131c087>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131c087>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131c087>] watchdog+0x5f7/0xa40 kernel/hung_task.c:239
 [<ffffffff81142028>] kthread+0x278/0x310 kernel/kthread.c:211
 [<ffffffff82816c5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 1908 Comm: rsyslogd Not tainted 4.9.155+ #27
task: ffff8801d389af80 task.stack: ffff8801d3a68000
RIP: 0010:[<ffffffff812080aa>] 
c [<ffffffff812080aa>] __lock_acquire+0xa2a/0x4350 kernel/locking/lockdep.c:3325
RSP: 0018:ffff8801d3a6f790  EFLAGS: 00000097
RAX: ffff8801d389b820 RBX: 0000000000000069 RCX: 1ffff1003a71370a
RDX: ffff8801d389b820 RSI: ffff8801d389b830 RDI: ffffffff83c7a970
RBP: ffff8801d3a6f918 R08: 0000000000000001 R09: ffff8801d389b850
R10: ffff8801d389b830 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000069 R14: 0000000000000000 R15: ffff8801d389af80
FS:  00007fd7edbf9700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9104fe0000 CR3: 00000001d3d04000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 000a0018d389b820
c ffff8801db721030
c ffff880100000009
c ffff8801db721018
c
 0000000041b58ab3
c ffffffff82e32630
c ffffffff811ff9a0
c ffff8801d3a6f808
c
 ffffffff81babb7c
c 00000000d3a6f8a0
c 000060fe24600408
c ffffffff830bdc80
c
Call Trace:
 [<ffffffff8120c493>] lock_acquire+0x133/0x3d0 kernel/locking/lockdep.c:3756
 [<ffffffff82815fe0>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
 [<ffffffff82815fe0>] _raw_spin_lock_irqsave+0x50/0x70 kernel/locking/spinlock.c:159
 [<ffffffff81173b01>] try_to_wake_up+0x91/0xfb0 kernel/sched/core.c:2045
 [<ffffffff81174ad5>] wake_up_process kernel/sched/core.c:2205 [inline]
 [<ffffffff81174ad5>] wake_up_q+0x95/0xf0 kernel/sched/core.c:483
 [<ffffffff8129cd89>] futex_wake+0x3b9/0x460 kernel/futex.c:1454
 [<ffffffff812a071f>] do_futex+0x2bf/0x1a70 kernel/futex.c:3274
 [<ffffffff812a2123>] SYSC_futex kernel/futex.c:3330 [inline]
 [<ffffffff812a2123>] SyS_futex+0x253/0x360 kernel/futex.c:3298
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff82816a93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c