INFO: task syz.3.5770:19451 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.3.5770      state:D stack:27744 pid:19451 tgid:19449 ppid:12526  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d4/0x5630
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7c1/0x1550
 sync_bdevs+0x276/0x470
 __ia32_sys_sync+0xc5/0x120
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f114a59e159
RSP: 002b:00007f114b4bb028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f114a826090 RCX: 00007f114a59e159
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f114a826090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f114a826128 R14: 00007f114a826090 R15: 00007ffddfdd6c88
 </TASK>

Showing all locks held in the system:
locks held by kworker/0:0/9: 4, last CPU#0:
 #0: ffff88812103b2e0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160
 #1: ffff888121024408 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0
 #2: ffff888121043358 (&ACCESS_PRIVATE(sdp, lock)){....}-{2:2}, at: srcu_invoke_callbacks+0x3a2/0x5a0
 #3: ffff888103e86498 (&p->pi_lock){-.-.}-{2:2}, at: try_to_wake_up+0x63/0x14d0
locks held by khungtaskd/35: 1, last CPU#0:
 #0: ffffffff8eb5a0e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
locks held by getty/5419: 2, on CPU#1:
 #0: ffff88816f0970a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900028c02e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360
locks held by udevd/5782: 1, on CPU#0:
 #0: ffff88816da56350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70
locks held by kworker/0:8/5792: 3, on CPU#0:
 #0: ffff88823c484f40 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0xa1a/0x14c0
 #1: ffffc90006837c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0xa1a/0x14c0
 #2: ffff888106f581d8 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4d30
locks held by syz.3.5770/19451: 1, on CPU#0:
 #0: ffff88816da56350 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470
locks held by syz.2.6211/20521: 1, on CPU#0:
 #0: ffff88816da56350 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470
locks held by syz.2.6211/20523: 1, on CPU#0:
 #0: ffff88816da56350 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 35 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+0x17d/0x390
 sys_info+0x135/0x170
 watchdog+0xfd7/0x1030
 kthread+0x38b/0x480
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
