INFO: task syz.3.477:10000 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.477       state:D stack:28328 pid:10000 tgid:9999  ppid:9214   task_flags:0x400140 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x5fd/0x8f0
 down_read+0x98/0x2e0
 super_lock+0x2a9/0x3b0
 __iterate_supers+0x126/0x290
 ksys_sync+0x94/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff67978ebe9
RSP: 002b:00007ff67a6c2038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007ff6799c5fa0 RCX: 00007ff67978ebe9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ff6799c5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff6799c6038 R14: 00007ff6799c5fa0 R15: 00007fff8fc1a0a8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/35:
 #0: ffffffff8e139f20 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5678:
 #0: ffff8880206830a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900029062f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
5 locks held by kworker/u8:5/6599:
 #0: ffff88801b2f7148 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90002befbc0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffffffff8f52cc50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x800
 #3: ffffffff8f539b08 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x2a4/0x990
 #4: ffffffff8e13f9b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730
3 locks held by kworker/0:7/7008:
 #0: ffff88801a480d48 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc900029efbc0 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888108829240 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x26b/0x3180
3 locks held by kworker/0:8/7672:
 #0: ffff88801a480d48 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90003fb7bc0 (deferred_process_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffffffff8f539b08 (rtnl_mutex){+.+.}-{4:4}, at: switchdev_deferred_process_work+0xe/0x20
2 locks held by syz-executor/7894:
1 lock held by syz.3.477/10000:
 #0: ffff8881224f20e0 (&type->s_umount_key#54){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
1 lock held by syz-executor/11906:
 #0: ffffffff8e13f9b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 35 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+0xf93/0xfe0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 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: 11906 Comm: syz-executor 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:io_serial_in+0x77/0xc0
Code: e8 1e 41 70 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 b2 d3 fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 cc cc cc cc cc 44 89 f9 80 e1 07
RSP: 0018:ffffc900031f7098 EFLAGS: 00000006
RAX: 1ffffffff33bea05 RBX: 00000000000003f9 RCX: 0000000000000000
RDX: 00000000000003f9 RSI: 0000000000000000 RDI: 0000000000000020
RBP: ffffc900031f7270 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff854f6d70 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff99df5420 R15: 0000000000000000
FS:  0000555591264500(0000) GS:ffff8881a3c15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f13f4d440 CR3: 0000000040aee000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 serial8250_console_write+0x584/0x1ba0
 console_flush_all+0x728/0xc40
 console_unlock+0xc4/0x270
 vprintk_emit+0x5b7/0x7a0
 __bch2_print+0x176/0x220
 bch2_fs_read_only+0x419/0xb00
 __bch2_fs_stop+0x100/0x900
 generic_shutdown_super+0x135/0x2c0
 bch2_kill_sb+0x41/0x50
 deactivate_locked_super+0xbc/0x130
 cleanup_mnt+0x425/0x4c0
 task_work_run+0x1d4/0x260
 do_exit+0x6b5/0x2300
 do_group_exit+0x21c/0x2d0
 get_signal+0x1286/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 exit_to_user_mode_loop+0x75/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fec5a1c14a5
Code: Unable to access opcode bytes at 0x7fec5a1c147b.
RSP: 002b:00007ffcde9260c0 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: 0000000000000000 RBX: 0000000000000010 RCX: 00007fec5a1c14a5
RDX: 00007ffcde926100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffcde92616c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000005
R13: 000000000000004c R14: 0000000000068101 R15: 00007ffcde9261c0
 </TASK>
