INFO: task loop7:16263 blocked for more than 120 seconds.
      Not tainted 4.9.103-g7fd4075 #39
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
loop7           D27080 16263      2 0x00000000
 ffff8801c49d8000 0000000000000000 ffff8801c0ef3480 ffff8801d761c800
 ffff8801db321c18 ffff88018f026df0 ffffffff839e711d 0000000041b58ab3
 ffffffff843c1ce8 ffffffff812364d0 0000000000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839e871f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f4b31>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff839e68fa>] io_schedule_timeout+0x1ba/0x390 kernel/sched/core.c:5180
 [<ffffffff81e5158c>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff81e5158c>] bt_get.isra.8+0x27c/0x780 block/blk-mq-tag.c:141
 [<ffffffff81e5249c>] __blk_mq_get_tag block/blk-mq-tag.c:163 [inline]
 [<ffffffff81e5249c>] blk_mq_get_tag+0xac/0x220 block/blk-mq-tag.c:192
 [<ffffffff81e41bca>] __blk_mq_alloc_request+0x2a/0xaa0 block/blk-mq.c:196
 [<ffffffff81e43fcb>] blk_mq_map_request.isra.38+0x3ab/0x900 block/blk-mq.c:1207
 [<ffffffff81e4c416>] blk_sq_make_request+0x1d6/0x1220 block/blk-mq.c:1374
 [<ffffffff81e1f34e>] generic_make_request+0x20e/0x9b0 block/blk-core.c:2055
 [<ffffffff81e1fba0>] submit_bio+0xb0/0x460 block/blk-core.c:2126
 [<ffffffff8164331a>] dio_bio_submit fs/direct-io.c:420 [inline]
 [<ffffffff8164331a>] do_blockdev_direct_IO+0x35da/0x5a80 fs/direct-io.c:1301
 [<ffffffff81645865>] __blockdev_direct_IO+0xa5/0xd0 fs/direct-io.c:1360
 [<ffffffff8162f410>] blkdev_direct_IO+0xa0/0xd0 fs/block_dev.c:183
 [<ffffffff8143e890>] generic_file_read_iter+0x660/0x1a90 mm/filemap.c:1951
 [<ffffffff81632015>] blkdev_read_iter+0x105/0x170 fs/block_dev.c:1738
 [<ffffffff825cd3b3>] lo_rw_aio+0x6b3/0x8a0 drivers/block/loop.c:506
 [<ffffffff825cd977>] do_req_filebacked drivers/block/loop.c:543 [inline]
 [<ffffffff825cd977>] loop_handle_cmd drivers/block/loop.c:1698 [inline]
 [<ffffffff825cd977>] loop_queue_work+0x3d7/0x2320 drivers/block/loop.c:1710
 [<ffffffff8119d289>] kthread_worker_fn+0x249/0x6b0 kernel/kthread.c:627
 [<ffffffff8119cead>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f81dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
2 locks held by kworker/0:0/4:
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118ce8e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118ce8e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118ce8e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118ce8e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  (binder_deferred_work){+.+...}, at: [<ffffffff8118cec8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136688c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136688c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425e10>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f61c2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211f1d2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.103-g7fd4075 #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d847fd08 ffffffff81eb34a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9590 ffff8801d847fd40
 ffffffff81ebe7a7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb34a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb34a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe7a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe73a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9694>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366e24>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366e24>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366e24>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366e24>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119cead>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f81dc>] 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: 16310 Comm: udevd Not tainted 4.9.103-g7fd4075 #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88019b54e000 task.stack: ffff8801bb060000
RIP: 0010:[<ffffffff8122ff30>] 
c [<ffffffff8122ff30>] match_held_lock+0x0/0x570 kernel/locking/lockdep.c:1294
RSP: 0018:ffff8801bb067900  EFLAGS: 00000002
RAX: 0000000000000005 RBX: ffffffff846def20 RCX: ffff88019b54e000
RDX: 0000000000000004 RSI: ffffffff846def20 RDI: ffff88019b54e918
RBP: ffff8801bb0679b0 R08: ffff88019b54e938 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff100336a9d22 R12: dffffc0000000000
R13: ffff88019b54e918 R14: ffff88019b54e8f0 R15: 0000000000000002
FS:  00007f7edcaf17a0(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7edcaf7000 CR3: 00000001d0466000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8123b4d5
c 0dd28929890732b2
c 0000000000000046
c ffff88019b54e000
c
 0000000000000000
c 0000000000000000
c 0000000000000002
c ffff8801bb0679b0
c
 ffff8801bb067980
c ffffffff81f1af0b
c ffff88019b54e8c0
c ffff88019b54e8c8
c
Call Trace:
 [<ffffffff81cf591e>] rcu_lock_release include/linux/rcupdate.h:498 [inline]
 [<ffffffff81cf591e>] rcu_read_unlock include/linux/rcupdate.h:931 [inline]
 [<ffffffff81cf591e>] avc_reclaim_node security/selinux/avc.c:542 [inline]
 [<ffffffff81cf591e>] avc_alloc_node+0x27e/0x3d0 security/selinux/avc.c:561
 [<ffffffff81cf6578>] avc_insert security/selinux/avc.c:672 [inline]
 [<ffffffff81cf6578>] avc_compute_av+0x178/0x610 security/selinux/avc.c:978
 [<ffffffff81cf8654>] avc_has_perm_noaudit security/selinux/avc.c:1114 [inline]
 [<ffffffff81cf8654>] avc_has_perm+0x364/0x4f0 security/selinux/avc.c:1148
 [<ffffffff81d131e7>] current_has_perm+0x1e7/0x2e0 security/selinux/hooks.c:1631
 [<ffffffff81d134dc>] selinux_task_create+0x1c/0x20 security/selinux/hooks.c:3701
 [<ffffffff81cf0893>] security_task_create+0x73/0xb0 security/security.c:894
 [<ffffffff8112de74>] copy_process.part.51+0x214/0x6330 kernel/fork.c:1521
 [<ffffffff81134410>] copy_process kernel/fork.c:1497 [inline]
 [<ffffffff81134410>] _do_fork+0x1b0/0xdc0 kernel/fork.c:1955
 [<ffffffff811350f7>] SYSC_clone kernel/fork.c:2065 [inline]
 [<ffffffff811350f7>] SyS_clone+0x37/0x50 kernel/fork.c:2059
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f8013>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c