INFO: task syz.6.5465:20085 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.6.5465      state:D stack:28424 pid:20085 tgid:20084 ppid:8261   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 cgroup_lock_and_drain_offline+0x51a/0x650
 cgroup_kn_lock_live+0x120/0x230
 cgroup_subtree_control_write+0x4b5/0x1080
 cgroup_file_write+0x331/0x8f0
 kernfs_fop_write_iter+0x3a4/0x540
 vfs_write+0x612/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd85df9e0d9
RSP: 002b:00007fd85eec1028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd85e225fa0 RCX: 00007fd85df9e0d9
RDX: 0000000000000005 RSI: 0000200000000140 RDI: 0000000000000005
RBP: 00007fd85e035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd85e226038 R14: 00007fd85e225fa0 R15: 00007ffd88880ea8
 </TASK>
INFO: task syz.6.5465:20088 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.6.5465      state:D stack:28808 pid:20088 tgid:20084 ppid:8261   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 fdget_pos+0x246/0x320
 ksys_write+0x79/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd85df9e0d9
RSP: 002b:00007fd85eea0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd85e226090 RCX: 00007fd85df9e0d9
RDX: 0000000000000005 RSI: 0000200000000040 RDI: 0000000000000005
RBP: 00007fd85e035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd85e226128 R14: 00007fd85e226090 R15: 00007ffd88880ea8
 </TASK>

Showing all locks held in the system:
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/5426:
 #0: 
ffff88811363c0a0
 (
&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
6 locks held by syz.3.3050/13593:
3 locks held by syz.6.5465/20085:
 #0: ffff8881bde406f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff888173776450 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffff88817270d480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540
1 lock held by syz.6.5465/20088:
 #0: ffff8881bde406f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
6 locks held by kworker/u10:19/21736:
1 lock held by syz-executor/21924:

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

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>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 13593 Comm: syz.3.3050 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: 0010:io_serial_in+0x77/0xc0
Code: e8 fe 09 5f fc 44 89 f9 d3 e3 49 83 c6 40 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 8f be cd fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f e9 0a 62 6b 06 cc 44 89 f9 80 e1 07
RSP: 0018:ffffc9000898f0b8 EFLAGS: 00000006
RAX: 1ffffffff355aa05 RBX: 00000000000003f9 RCX: 0000000000000000
RDX: 00000000000003f9 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc9000898f250 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff8567e110 R12: dffffc0000000000
R13: ffffffff9aad5140 R14: ffffffff9aad5180 R15: 0000000000000000
FS:  00007f494d18e6c0(0000) GS:ffff8882a8f56000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555793c7a28 CR3: 00000001122a4000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 serial8250_console_write+0x503/0x1ba0
 console_flush_all+0x6ea/0xaf0
 console_unlock+0xd1/0x1c0
 vprintk_emit+0x485/0x560
 _printk+0xdd/0x130
 __nilfs_msg+0x373/0x450
 nilfs_clean_segments+0x6f2/0xbb0
 nilfs_ioctl+0x2619/0x2780
 __se_sys_ioctl+0xfc/0x170
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f494c39e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f494d18e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f494c625fa0 RCX: 00007f494c39e0d9
RDX: 0000200000000040 RSI: 0000000040786e88 RDI: 0000000000000004
RBP: 00007f494c435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f494c626038 R14: 00007f494c625fa0 R15: 00007ffc1a3f65a8
 </TASK>
