INFO: task syz-executor4:6156 blocked for more than 140 seconds.
      Not tainted 4.9.112-g9e79039 #59
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D28488  6156   3854 0x00000004
 ffff8801d38b9800 ffff8801d532c540 ffff8801cf6539c0 ffff8801d02f3000
 ffff8801db321c18 ffff8801d4f2faa0 ffffffff839e907d 1ffff1003a9e5f48
 ffffffff85542200 0000000041b58ab3 00ffffff843c36c0 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea67f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f6a91>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff839e885a>] io_schedule_timeout+0x1ba/0x390 kernel/sched/core.c:5180
 [<ffffffff839ebfb3>] do_wait_for_common kernel/sched/completion.c:75 [inline]
 [<ffffffff839ebfb3>] __wait_for_common kernel/sched/completion.c:93 [inline]
 [<ffffffff839ebfb3>] wait_for_common_io kernel/sched/completion.c:107 [inline]
 [<ffffffff839ebfb3>] wait_for_completion_io+0x203/0x2e0 kernel/sched/completion.c:155
 [<ffffffff81dfa9e2>] submit_bio_wait+0x112/0x180 block/bio.c:885
 [<ffffffff81e2d132>] blkdev_issue_flush+0x152/0x220 block/blk-flush.c:518
 [<ffffffff8162f1e5>] blkdev_fsync+0x85/0xb0 fs/block_dev.c:378
 [<ffffffff8161a7ec>] vfs_fsync_range+0x10c/0x260 fs/sync.c:195
 [<ffffffff8161a9b2>] vfs_fsync fs/sync.c:209 [inline]
 [<ffffffff8161a9b2>] do_fsync+0x42/0xb0 fs/sync.c:219
 [<ffffffff8161b159>] SYSC_fdatasync fs/sync.c:233 [inline]
 [<ffffffff8161b159>] SyS_fdatasync+0x19/0x20 fs/sync.c:231
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f53>] 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: [<ffffffff8136675c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136675c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425de7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3772:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8122>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211edc2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.112-g9e79039 #59
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d84cfd08 ffffffff81eb3249 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d84cfd40
 ffffffff81ebe547 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb3249>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3249>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe547>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe4da>] 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
 [<ffffffff81366cf4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366cf4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366cf4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366cf4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa11c>] 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 0xffffffff839f8b86