INFO: task syz.7.4426:17090 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.7.4426      state:D stack:28456 pid:17090 tgid:17089 ppid:10952  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 nfsd_shutdown_threads+0x4e/0xd0
 nfsd_umount+0x41/0x60
 deactivate_locked_super+0xbc/0x130
 cleanup_mnt+0x3d3/0x460
 task_work_run+0x1d9/0x270
 exit_to_user_mode_loop+0x1fa/0x730
 do_syscall_64+0x353/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdabe99e019
RSP: 002b:00007fdabf82d028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: fffffffffffffffe RBX: 00007fdabec25fa0 RCX: 00007fdabe99e019
RDX: 0000200000000080 RSI: 0000200000000040 RDI: 0000000000000000
RBP: 00007fdabea3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdabec26038 R14: 00007fdabec25fa0 R15: 00007ffdab52a048
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/36:
 #0: ffffffff8eb59ca0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5440:
 #0: ffff88810f6130a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034732e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360
3 locks held by syz.4.1802/10752:
 #0: ffff88816fd872f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff88811542e450 (sb_writers#39){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8e6e0 (nfsd_mutex){+.+.}-{4:4}, at: write_ports+0xb5/0xd10
2 locks held by syz.7.4426/17090:
 #0: ffff8881a8ca40d8 (&type->s_umount_key#102){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8ee8e6e0 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x4e/0xd0

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 36 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: 0 Comm: swapper/1 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:pv_native_safe_halt+0xf/0x20
Code: 3c 7e 02 e9 d3 06 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d b3 dd 17 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffc90000197e40 EFLAGS: 00000202
RAX: 000000000065b249 RBX: ffffffff819b4060 RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e22dd4d RDI: ffffffff8c4be180
RBP: ffffc90000197f10 R08: ffff88823c6338db R09: 1ffff110478c671b
R10: dffffc0000000000 R11: ffffed10478c671c R12: 0000000000000000
R13: 1ffff1102c096000 R14: 1ffff92000032fd0 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8882a8f4d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f44bb4ccff8 CR3: 0000000113fac000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 default_idle+0x9/0x20
 default_idle_call+0x72/0xb0
 do_idle+0x2e0/0x540
 cpu_startup_entry+0x43/0x60
 start_secondary+0x101/0x110
 common_startup_64+0x13e/0x157
 </TASK>
