INFO: task syz.4.4452:27458 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.4452      state:D stack:25544 pid:27458 tgid:27457 ppid:26616  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 sync_bdevs+0x276/0x470
 __ia32_sys_sync+0xc5/0x120
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa5c059e0d9
RSP: 002b:00007fa5c1504028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fa5c0825fa0 RCX: 00007fa5c059e0d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fa5c0825fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa5c0826038 R14: 00007fa5c0825fa0 R15: 00007ffcf98f3af8
 </TASK>
INFO: task syz.4.4452:27459 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.4452      state:D stack:28552 pid:27459 tgid:27457 ppid:26616  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 sync_bdevs+0x276/0x470
 __ia32_sys_sync+0xc5/0x120
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa5c059e0d9
RSP: 002b:00007fa5c14e3028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fa5c0826090 RCX: 00007fa5c059e0d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fa5c0826090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa5c0826128 R14: 00007fa5c0826090 R15: 00007ffcf98f3af8
 </TASK>
INFO: task syz.4.4452:27460 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.4452      state:D stack:24648 pid:27460 tgid:27457 ppid:26616  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 sync_bdevs+0x276/0x470
 __ia32_sys_sync+0xc5/0x120
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa5c059e0d9
RSP: 002b:00007fa5c14c2028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fa5c0826180 RCX: 00007fa5c059e0d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fa5c0826180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa5c0826218 R14: 00007fa5c0826180 R15: 00007ffcf98f3af8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by kworker/u12:0/55:
 #0: ffff88810a984940 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc9000141fc40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
8 locks held by kworker/1:2/984:
 #0: ffff8881052f6540 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc90006607c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #2: ffff88816bf4a1d8 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4d30
 #3: ffff88816b6261d8 (&dev->mutex){....}-{4:4}, at: usb_disconnect+0xfc/0x9a0
 #4: ffff8881bc1af1a0 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb9/0x880
 #5: ffff8881b6751a58 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb9/0x880
 #6: ffffffff8fa9f140 (input_mutex){+.+.}-{4:4}, at: __input_unregister_device+0x2d8/0x650
 #7: ffffffff8eb5ff68 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770
2 locks held by getty/5425:
 #0: ffff888113f580a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034762e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360
1 lock held by udevd/7012:
 #0: ffff88810a6b9350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70
2 locks held by kworker/u12:1/15710:
 #0: ffff88810a984940 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc90006b07c40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
1 lock held by syz.4.4452/27458:
 #0: ffff88810a6b9350 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470
1 lock held by syz.4.4452/27459:
 #0: ffff88810a6b9350 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470
1 lock held by syz.4.4452/27460:
 #0: ffff88810a6b9350 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470
5 locks held by kworker/u10:32/29203:
1 lock held by syz.9.5193/30624:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 34 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
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+0xe8/0x150
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x380
 sys_info+0x135/0x170
 watchdog+0xfd7/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 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: 5046 Comm: udevd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0033:0x7f5f50cd9643
Code: ff 0f 00 00 48 81 f9 cf 0f 00 00 77 6a f3 0f 6f 20 66 0f 74 e0 66 0f d7 d4 85 d2 74 04 0f bc c2 c3 48 83 e0 f0 66 0f 74 48 10 <66> 0f 74 50 20 66 0f 74 58 30 66 0f d7 d1 66 44 0f d7 c2 66 0f d7
RSP: 002b:00007ffd2f51d0e8 EFLAGS: 00000206
RAX: 00005629a5acb900 RBX: 00005629a5ae0ab0 RCX: 0000000000000904
RDX: 0000000000000000 RSI: 0000562988aecc3d RDI: 00005629a5acb904
RBP: 00005629a5acb904 R08: 00005629a5adfa10 R09: 00007f5f50df1b10
R10: 0000000000000010 R11: 0000000000000000 R12: fffffffffffffffe
R13: 00005629a5acb904 R14: 00005629a5adfa10 R15: 0000562988af3401
FS:  00007f5f51139c80 GS:  0000000000000000
