INFO: task syz.2.1739:10815 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.1739      state:D stack:27904 pid:10815 tgid:10814 ppid:5853   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7e6/0x1350
 sync_bdevs+0x1ac/0x340
 ksys_sync+0xb9/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f35ccf8eba9
RSP: 002b:00007f35cb1f6038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f35cd1d5fa0 RCX: 00007f35ccf8eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f35cd1d5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f35cd1d6038 R14: 00007f35cd1d5fa0 R15: 00007ffead847cf8
 </TASK>
INFO: task syz.2.1739:10816 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.1739      state:D stack:27904 pid:10816 tgid:10814 ppid:5853   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7e6/0x1350
 sync_bdevs+0x1ac/0x340
 ksys_sync+0xb9/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f35ccf8eba9
RSP: 002b:00007f35cb1d5038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f35cd1d6090 RCX: 00007f35ccf8eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f35cd1d6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f35cd1d6128 R14: 00007f35cd1d6090 R15: 00007ffead847cf8
 </TASK>

Showing all locks held in the system:
6 locks held by kworker/0:0/9:
 #0: ffff88801bbfad48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc900000c7ba0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: 
ffff88813647e198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a20
 #3: ffff88803031b198 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400
 #4: ffff888030319160 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400
 #5: ffff88804b03a018 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140
1 lock held by khungtaskd/34:
 #0: ffffffff8e33d660 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5672:
 #0: ffff8880295a50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc9000290e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
1 lock held by udevd/5849:
 #0: ffff888108069358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30
5 locks held by kworker/0:3/5886:
 #0: ffff88801bbfad48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90003267ba0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888104b45198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a20
 #3: ffff888104b43518 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_event+0x21b8/0x4a20
 #4: ffff88810ab72268 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_event+0x21e5/0x4a20
5 locks held by kworker/1:4/5901:
 #0: ffff88801bbfad48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc900033b7ba0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888023756198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a20
 #3: ffff88810a169518 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_event+0x21b8/0x4a20
 #4: ffff888107ed3c68 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_event+0x21e5/0x4a20
1 lock held by syz.2.1739/10815:
 #0: ffff888108069358 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x1ac/0x340
1 lock held by syz.2.1739/10816:
 #0: ffff888108069358 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x1ac/0x340
1 lock held by syz.5.2000/11648:
 #0: ffff888108069358 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x1ac/0x340

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 34 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 nmi_cpu_backtrace+0x39e/0x3d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf60/0xfa0
 kthread+0x711/0x8a0
 ret_from_fork+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:pv_native_safe_halt+0x13/0x20
Code: cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 03 2c 24 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000177de0 EFLAGS: 00000282
RAX: 917cac98c8cdb400 RBX: ffffffff81969548 RCX: 917cac98c8cdb400
RDX: 0000000000000001 RSI: ffffffff8dbc0fba RDI: ffffffff8c038200
RBP: ffffc90000177f10 R08: ffff888136632fdb R09: 1ffff11026cc65fb
R10: dffffc0000000000 R11: ffffed1026cc65fc R12: ffffffff8fc43c30
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff110200d4000
FS:  0000000000000000(0000) GS:ffff8881a39e0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32614ff8 CR3: 000000010de06000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 default_idle+0x13/0x20
 default_idle_call+0x74/0xb0
 do_idle+0x1e8/0x510
 cpu_startup_entry+0x44/0x60
 start_secondary+0x101/0x110
 common_startup_64+0x13e/0x147
 </TASK>
