INFO: task syz.4.10521:560 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.4.10521     state:D stack:27496 pid:560   tgid:559   ppid:21217  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: 0033:0x7ffa77f9e0d9
RSP: 002b:00007ffa78db3028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: fffffffffffffffe RBX: 00007ffa78225fa0 RCX: 00007ffa77f9e0d9
RDX: 0000200000000040 RSI: 0000200000000000 RDI: 0000000000000000
RBP: 00007ffa78035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffa78226038 R14: 00007ffa78225fa0 R15: 00007ffcbd574b58
 </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/5432:
 #0: ffff8881709480a0 (&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
3 locks held by syz.0.10224/32171:
 #0: ffff888114b83ef0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff888115c9c450 (sb_writers#18){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8dd80 (nfsd_mutex){+.+.}-{4:4}, at: write_ports+0xb5/0xd10
2 locks held by syz.4.10521/560:
 #0: ffff8881192b20d8 (&type->s_umount_key#73){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8ee8dd80 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x4e/0xd0
1 lock held by syz-executor/1000:
 #0: ffff88812103b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160
2 locks held by syz.8.11854/3871:
 #0: ffff88811742e0d8 (&type->s_umount_key#73){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8ee8dd80 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x4e/0xd0

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

NMI backtrace for cpu 1
CPU: 1 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 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: bb 7e 02 c3 cc cc cc cc 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 be 18 00 fb f4 <e9> 4c 07 03 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e807de0 EFLAGS: 00000202
RAX: 00000000007b6def RBX: ffffffff819b4450 RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e228b3b RDI: ffffffff8c4bbe80
RBP: ffffffff8e807eb8 R08: ffff8881210338db R09: 1ffff1102420671b
R10: dffffc0000000000 R11: ffffed102420671c R12: 0000000000000000
R13: 1ffffffff1d11de8 R14: 1ffffffff1d00fc4 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff88818d954000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f50babf14b8 CR3: 000000016a676000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 default_idle+0x9/0x20
 default_idle_call+0x72/0xb0
 do_idle+0x2e0/0x540
 cpu_startup_entry+0x43/0x60
 rest_init+0x2de/0x300
 start_kernel+0x392/0x3e0
 x86_64_start_reservations+0x24/0x30
 x86_64_start_kernel+0x137/0x1b0
 common_startup_64+0x13e/0x157
 </TASK>
