INFO: task kworker/u9:1:28 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u9:1    state:D stack:22600 pid:28    tgid:28    ppid:2      task_flags:0x4208160 flags:0x00080000
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 n_tty_receive_char+0x5f9/0xbd0
 n_tty_receive_buf_standard+0x754/0x6a50
 n_tty_receive_buf_common+0xb33/0x13d0
 tty_port_default_receive_buf+0x6e/0xa0
 flush_to_ldisc+0x247/0x6c0
 process_scheduled_works+0xa8e/0x14e0
 worker_thread+0xa47/0xfb0
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Showing all locks held in the system:
6 locks held by kworker/u9:1/28:
 #0: ffff8881000ac140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc90000a37c40 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #2: ffff88810068a0b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x38/0x6c0
 #3: ffff88811e9f00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1c/0x90
 #4: ffff88811e9f02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x84/0x13d0
 #5: ffffc90004405370 (&ldata->output_lock){+.+.}-{4:4}, at: n_tty_receive_char+0x5f9/0xbd0
1 lock held by khungtaskd/35:
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5466:
 #0: ffff888172db20a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034832e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360
2 locks held by syz.0.1247/8819:
6 locks held by syz.5.2165/11165:
1 lock held by udevd/12695:
7 locks held by syz.6.2701/12708:
 #0: ffff88810628a6f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff88801d14e450 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffff8881749d0480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540
 #3: ffffffff8f3a1d60 (pci_rescan_remove_lock){+.+.}-{4:4}, at: pci_stop_and_remove_bus_device_locked+0x13/0xb0
 #4: ffff888104ee41f8 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb9/0x880
 #5: ffff888169414260 (&dev->clientlist_mutex){+.+.}-{4:4}, at: drm_client_dev_unregister+0xa1/0x2d0
 #6: ffffffff8f3c90a0 (registration_lock){+.+.}-{4:4}, at: unregister_framebuffer+0x2e/0x3b0
3 locks held by syz-executor/12881:
3 locks held by syz.7.2790/12922:
4 locks held by syz-executor/12925:

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

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+0x17a/0x380
 sys_info+0x135/0x170
 watchdog+0xfd7/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
