INFO: task syz-executor6:12077 blocked for more than 140 seconds.
      Not tainted 4.9.119-g9dc978d #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D28656 12077   3781 0x00000004
 ffff88019852b000 ffff8801d835df80 ffff8801d835df80 ffff8801cc848000
 ffff8801db321c18 ffff880197ce7ab8 ffffffff839ebdcd ffffffff81235627
 0000000000000000 ffff88019852b8c0 0000000600000007 ffff8801db3224e8
Call Trace:
 [<ffffffff839ed3cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839f8a08>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839f8a08>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81ee8ec7>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff8122c250>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff8122c250>] down_write_nested+0x60/0xa0 kernel/locking/rwsem.c:174
 [<ffffffff815aadf1>] inode_lock_nested include/linux/fs.h:801 [inline]
 [<ffffffff815aadf1>] do_unlinkat+0x2a1/0x680 fs/namei.c:4067
 [<ffffffff815acd0a>] SYSC_unlink fs/namei.c:4128 [inline]
 [<ffffffff815acd0a>] SyS_unlink+0x1a/0x20 fs/namei.c:4126
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81426027>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/3578:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d859c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157307e>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157307e>] vfs_write+0x3ae/0x530 fs/read_write.c:556
1 lock held by rsyslogd/3580:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d859c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3676:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fae72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821208d2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor6/11991:
 #0:  (sb_writers#20){.+.+.+}, at: [<ffffffff815e0e3f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#20){.+.+.+}, at: [<ffffffff815e0e3f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#19/1){+.+.+.}, at: [<ffffffff815aadf1>] inode_lock_nested include/linux/fs.h:801 [inline]
 #1:  (&sb->s_type->i_mutex_key#19/1){+.+.+.}, at: [<ffffffff815aadf1>] do_unlinkat+0x2a1/0x680 fs/namei.c:4067
1 lock held by syz-executor6/12076:
 #0:  (&type->s_umount_key#54/1){+.+.+.}, at: [<ffffffff8157bda2>] alloc_super fs/super.c:241 [inline]
 #0:  (&type->s_umount_key#54/1){+.+.+.}, at: [<ffffffff8157bda2>] sget_userns+0x552/0xba0 fs/super.c:503
2 locks held by syz-executor6/12077:
 #0:  (sb_writers#20){.+.+.+}, at: [<ffffffff815e0e3f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#20){.+.+.+}, at: [<ffffffff815e0e3f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#19/1){+.+.+.}, at: [<ffffffff815aadf1>] inode_lock_nested include/linux/fs.h:801 [inline]
 #1:  (&sb->s_type->i_mutex_key#19/1){+.+.+.}, at: [<ffffffff815aadf1>] do_unlinkat+0x2a1/0x680 fs/namei.c:4067

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d96c7d08 ffffffff81eb4be9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d96c7d40
 ffffffff81ebfee7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfee7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe7a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366d54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fce9c>] 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 skipped: idling at pc 0xffffffff839fb8d6