INFO: task syz-executor2:17010 blocked for more than 140 seconds.
      Not tainted 4.9.113-g47bbcd6 #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D28632 17010   3874 0x00000004
 ffff880199f48000 0000000000000000 ffff8801cd330fc0 ffff8801cdd31800
 ffff8801db321c18 ffff8801a760f3e0 ffffffff839e909d ffffffff855ba770
 ffff880199f48930 0000000000004626 00ff880199f488e0 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839f6ab1>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff839ed863>] do_wait_for_common kernel/sched/completion.c:75 [inline]
 [<ffffffff839ed863>] __wait_for_common kernel/sched/completion.c:93 [inline]
 [<ffffffff839ed863>] wait_for_common kernel/sched/completion.c:101 [inline]
 [<ffffffff839ed863>] wait_for_completion+0x203/0x2e0 kernel/sched/completion.c:122
 [<ffffffff811897a4>] flush_work+0x3a4/0x6c0 kernel/workqueue.c:2846
 [<ffffffff811904fe>] __cancel_work_timer+0x17e/0x440 kernel/workqueue.c:2912
 [<ffffffff811907d7>] cancel_work_sync+0x17/0x20 kernel/workqueue.c:2947
 [<ffffffff839c3181>] p9_conn_destroy net/9p/trans_fd.c:857 [inline]
 [<ffffffff839c3181>] p9_fd_close+0x1f1/0x330 net/9p/trans_fd.c:883
 [<ffffffff839b4665>] p9_client_create+0x825/0x10a0 net/9p/client.c:1050
 [<ffffffff8195b563>] v9fs_session_init+0x333/0x13a0 fs/9p/v9fs.c:343
 [<ffffffff8194ce5d>] v9fs_mount+0x7d/0x810 fs/9p/vfs_super.c:130
 [<ffffffff8157e2ac>] mount_fs+0x28c/0x370 fs/super.c:1206
 [<ffffffff815ddad1>] vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff815e53f9>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff815e53f9>] do_new_mount fs/namespace.c:2513 [inline]
 [<ffffffff815e53f9>] do_mount+0x3c9/0x2740 fs/namespace.c:2835
 [<ffffffff815e814e>] SYSC_mount fs/namespace.c:3051 [inline]
 [<ffffffff815e814e>] SyS_mount+0xfe/0x110 fs/namespace.c:3028
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] 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 rs:main Q:Reg/3678:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff81572cce>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff81572cce>] vfs_write+0x3ae/0x530 fs/read_write.c:556
2 locks held by getty/3776:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee22>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by kworker/1:3/12853:
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118d08e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118d08e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118d08e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events"){.+.+.+}, at: [<ffffffff8118d08e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&m->wq)){+.+.+.}, at: [<ffffffff8118d0c8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8a9fd08 ffffffff81eb32a9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d8a9fd40
 ffffffff81ebe5a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe53a>] 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
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84629800 task.stack: ffffffff84600000
RIP: 0010:[<ffffffff8122f0aa>] 
c [<ffffffff8122f0aa>] trace_hardirqs_off_caller+0x1ca/0x280 kernel/locking/lockdep.c:2776
RSP: 0018:ffff8801db207eb0  EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff8801db21cf00 RCX: 0000000000000000
RDX: 1ffffffff08c5412 RSI: 0000000000000000 RDI: ffffffff8462a090
RBP: ffff8801db207eb8 R08: ffffffff8462a0e8 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000001 R12: fffffbfff08c1b40
R13: ffffffff8460da00 R14: 0000000000000093 R15: fffffbfff08c1200
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c4303c3000 CR3: 00000001c8140000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffffffff8122f16d
c ffff8801db207f98
c ffffffff812cd38d
c ffffffff812ce384
c
 ffffffff8462a0c0
c ffff8801db207f18
c ffff8801db21cf74
c ffff8801db21cf60
c
 ffff8801db2180c0
c 1ffff1003b640fe2
c 0000000000000001
c 00000063cbdf84ab
c
Call Trace:
 [<ffffffff812cd38d>] seqcount_lockdep_reader_access include/linux/seqlock.h:82 [inline]
 [<ffffffff812cd38d>] read_seqcount_begin include/linux/seqlock.h:163 [inline]
 [<ffffffff812cd38d>] read_seqbegin include/linux/seqlock.h:433 [inline]
 [<ffffffff812cd38d>] tick_nohz_stop_sched_tick kernel/time/tick-sched.c:681 [inline]
 [<ffffffff812cd38d>] __tick_nohz_idle_enter+0x25d/0x1050 kernel/time/tick-sched.c:936
 [<ffffffff812ce384>] tick_nohz_irq_exit+0x84/0xb0 kernel/time/tick-sched.c:995
 [<ffffffff8114b291>] tick_irq_exit kernel/softirq.c:386 [inline]
 [<ffffffff8114b291>] irq_exit+0x151/0x190 kernel/softirq.c:407
 [<ffffffff839fe721>] smp_reschedule_interrupt+0x71/0x90 arch/x86/kernel/smp.c:270
 [<ffffffff839fc290>] reschedule_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:671
 <EOI> 
d [<ffffffff839f8ba6>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff839f81e5>] arch_safe_halt arch/x86/include/asm/paravirt.h:104 [inline]
 [<ffffffff839f81e5>] default_idle+0x55/0x360 arch/x86/kernel/process.c:437
 [<ffffffff8106ae00>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:428
 [<ffffffff839f9005>] default_idle_call+0x45/0x60 kernel/sched/idle.c:97
 [<ffffffff812231d5>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff812231d5>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff812231d5>] cpu_startup_entry+0x2b5/0x380 kernel/sched/idle.c:303
 [<ffffffff839e5e6c>] rest_init+0x183/0x189 init/main.c:409
 [<ffffffff84c97943>] start_kernel+0x67e/0x6b2 init/main.c:664
 [<ffffffff84c9629a>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff84c963db>] x86_64_start_kernel+0x13f/0x162 arch/x86/kernel/head64.c:177
Code: 
ca3 
c70 
c08 
c00 
c00 
c0f 
cb6 
c14 
c02 
c48 
c89 
cf8 
c83 
ce0 
c07 
c83 
cc0 
c03 
c38 
cd0 
c7c 
c08 
c84 
cd2 
c0f 
c85 
c97 
c00 
c00 
c00 
c44 
c89 
ca3 
c8c 
c08 
c00 
c00 
c5b 
c41 
c5c 
c41 
c5d 
c5d 
c<c3> 
ce8 
ca0 
ca7 
ccb 
c00 
c85 
cc0 
c74 
cf0 
c48 
cc7 
cc7 
c40 
c29 
cb9 
c85 
c48 
cb8 
c00 
c00 
c