INFO: task kworker/u4:7:4839 blocked for more than 140 seconds.
      Not tainted 4.9.124-g09eb2ba #31
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:7    D27256  4839      2 0x00000000
Workqueue: netns cleanup_net
 ffff8801975a0000 0000000000000000 ffff8801b9b7c540 ffffffff84629800
 ffff8801db221c18 ffff88019770f770 ffffffff839f0afd ffff880100000003
 fffffbff00000000 ffff8801975a0938 00ff880100000001 ffff8801db2224e8
Call Trace:
 [<ffffffff839f20ff>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839fe511>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff839f52c3>] do_wait_for_common kernel/sched/completion.c:75 [inline]
 [<ffffffff839f52c3>] __wait_for_common kernel/sched/completion.c:93 [inline]
 [<ffffffff839f52c3>] wait_for_common kernel/sched/completion.c:101 [inline]
 [<ffffffff839f52c3>] wait_for_completion+0x203/0x2e0 kernel/sched/completion.c:122
 [<ffffffff811a00c6>] kthread_stop+0xa6/0x5d0 kernel/kthread.c:519
 [<ffffffff830ff43e>] pg_net_exit+0x3de/0x6e0 net/core/pktgen.c:3923
 [<ffffffff83060f20>] ops_exit_list.isra.6+0xb0/0x160 net/core/net_namespace.c:136
 [<ffffffff83063df1>] cleanup_net+0x321/0x630 net/core/net_namespace.c:473
 [<ffffffff8118f461>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff81190256>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01b9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
2 locks held by kworker/u4:0/6:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
2 locks held by kworker/u4:1/22:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
2 locks held by kworker/u4:2/169:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
2 locks held by kworker/u4:3/426:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
2 locks held by khungtaskd/520:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813689dc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813689dc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81428248>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3761:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839ffba2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82125402>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/3849:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor2/3850:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor7/3851:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor3/3852:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor4/3853:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor5/3854:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor6/3855:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor1/3856:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
2 locks held by kworker/u4:5/4123:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
2 locks held by kworker/u4:6/4127:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
3 locks held by kworker/u4:7/4839:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff83063c0f>] cleanup_net+0x13f/0x630 net/core/net_namespace.c:439
2 locks held by kworker/u4:8/7044:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118f36e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&sub_info->work)){+.+.+.}, at: [<ffffffff8118f3a8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
1 lock held by kpktgend_0/7238:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by kpktgend_1/7242:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor4/7349:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor4/7360:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff83064255>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406
1 lock held by syz-executor4/7383:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor4/7435:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor4/7437:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff83064255>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406
1 lock held by syz-executor1/7359:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor1/7369:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor1/7382:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor1/7439:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor1/7440:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor7/7389:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor7/7402:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor7/7418:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor7/7433:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor3/7399:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor3/7405:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor3/7419:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor3/7441:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor3/7443:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor6/7401:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor6/7407:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor6/7424:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by modprobe/7415:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor5/7417:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor5/7423:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by blkid/7421:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor2/7422:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor2/7425:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor2/7444:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor2/7445:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor2/7446:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by modprobe/7426:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor0/7427:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor0/7429:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor0/7430:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by syz-executor0/7431:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by blkid/7428:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by modprobe/7432:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by modprobe/7434:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by loop4/7436:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
3 locks held by blkid/7438:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163530b>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1579
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825d31af>] lo_release+0x1f/0x1a0 drivers/block/loop.c:1606
 #2:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825d3215>] __lo_release drivers/block/loop.c:1584 [inline]
 #2:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825d3215>] lo_release+0x85/0x1a0 drivers/block/loop.c:1607
1 lock held by modprobe/7442:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by modprobe/7447:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328
1 lock held by modprobe/7448:
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #0:  ((task_exit_notifier).rwsem){.+.+..}, at: [<ffffffff811a5138>] blocking_notifier_call_chain+0x68/0xa0 kernel/notifier.c:328

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

NMI backtrace for cpu 0
CPU: 0 PID: 520 Comm: khungtaskd Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85b7d08 ffffffff81eb95e9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9fa0 ffff8801d85b7d40
 ffffffff81ec4927 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec4927>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec48ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810ba0a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81368f74>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81368f74>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368f74>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368f74>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01b9c>] 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 0xffffffff83a00606