INFO: task syz-executor0:8526 blocked for more than 120 seconds.
      Not tainted 4.9.78-g29eadc4 #20
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D29584  8526   3401 0x00000004
 ffff8801b1ef0000 0000000000000000 ffff8801cabed500 ffff8801cf2c6000
 ffff8801db321b98 ffff8801c99d7b00 ffffffff838a1bbb 0000000041b58ab3
 ffffffff84193238 00ffffff8123be20 ffff8801db322468 ffff8801db322490
Call Trace:
 [<ffffffff838a315f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838af2bc>] schedule_timeout+0x56c/0x10b0 kernel/time/timer.c:1768
 [<ffffffff838a136e>] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5172
 [<ffffffff838a4ace>] do_wait_for_common kernel/sched/completion.c:75 [inline]
 [<ffffffff838a4ace>] __wait_for_common kernel/sched/completion.c:93 [inline]
 [<ffffffff838a4ace>] wait_for_common_io kernel/sched/completion.c:107 [inline]
 [<ffffffff838a4ace>] wait_for_completion_io+0x20e/0x2e0 kernel/sched/completion.c:155
 [<ffffffff81cdac9b>] submit_bio_wait+0x11b/0x180 block/bio.c:885
 [<ffffffff81d0de47>] blkdev_issue_flush+0x157/0x220 block/blk-flush.c:518
 [<ffffffff81629fc5>] blkdev_fsync+0x85/0xb0 fs/block_dev.c:378
 [<ffffffff8161592a>] vfs_fsync_range+0x10a/0x250 fs/sync.c:195
 [<ffffffff81615ae2>] vfs_fsync fs/sync.c:209 [inline]
 [<ffffffff81615ae2>] do_fsync+0x42/0xb0 fs/sync.c:219
 [<ffffffff81616289>] SYSC_fdatasync fs/sync.c:233 [inline]
 [<ffffffff81616289>] SyS_fdatasync+0x19/0x20 fs/sync.c:231
 [<ffffffff838b2c6e>] entry_SYSCALL_64_fastpath+0x29/0xe8

Showing all locks held in the system:
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372df5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372df5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81237f80>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3308:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b0e32>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff820096f4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133

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

NMI backtrace for cpu 0
CPU: 0 PID: 515 Comm: khungtaskd Not tainted 4.9.78-g29eadc4 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8a87d00 ffffffff81d943a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810bac10 ffff8801d8a87d38
 ffffffff81d9f4cd 0000000000000000 0000000000000000 ffff8801cbc48418
Call Trace:
 [<ffffffff81d943a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d943a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9f4cd>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9f607>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bad04>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813733c0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813733c0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813733c0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813733c0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119a72d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b2fdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:477
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838b18a6