INFO: task syz.3.355:6909 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.3.355       state:D stack:27272 pid:6909  tgid:6902  ppid:5594   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x1259/0x6920 kernel/sched/core.c:7270
 __schedule_loop kernel/sched/core.c:7347 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7362
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7419
 __mutex_lock_common kernel/locking/mutex.c:726 [inline]
 __mutex_lock+0xccb/0x1bd0 kernel/locking/mutex.c:821
 nfsd_nrthreads+0x57/0xd0 fs/nfsd/nfssvc.c:252
 write_threads+0x34a/0x600 fs/nfsd/nfsctl.c:445
 nfsctl_transaction_write+0x106/0x1a0 fs/nfsd/nfsctl.c:114
 vfs_write+0x2aa/0x1050 fs/read_write.c:685
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f54c639e159
RSP: 002b:00007f54c72b6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f54c6626090 RCX: 00007f54c639e159
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f54c6435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f54c6626128 R14: 00007f54c6626090 R15: 00007fff554ca578
 </TASK>

Showing all locks held in the system:
locks held by pr/ttyS0/16: 2, last CPU#0:
 #0: ffffffff8edd8338 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:314 [inline]
 #0: ffffffff8edd8338 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:439 [inline]
 #0: ffffffff8edd8338 (console_srcu){....}-{0:0}, at: console_srcu_read_lock+0x49/0x60 kernel/printk/printk.c:291
 #1: ffffffff9bc60c78 (&port_lock_key){-.-.}-{3:3}, at: __uart_port_lock_irqsave include/linux/serial_core.h:613 [inline]
 #1: ffffffff9bc60c78 (&port_lock_key){-.-.}-{3:3}, at: univ8250_console_device_lock+0x64/0xc0 drivers/tty/serial/8250/8250_core.c:413
locks held by khungtaskd/31: 1, last CPU#1:
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6837
locks held by khugepaged/37: 1, last CPU#1:
 #0: ffffffff8ef55b80 (lock#5){+.+.}-{4:4}, at: __lru_add_drain_all+0xcf/0x820 mm/folio.c:822
locks held by kworker/u8:5/116: 3, on CPU#1:
 #0: ffff8880335de940 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x1466/0x1b10 kernel/workqueue.c:3362
 #1: ffffc900025d7d08 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3363
 #2: ffffffff90ccf180 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:134 [inline]
 #2: ffffffff90ccf180 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x11f/0x1360 net/ipv6/addrconf.c:4230
locks held by kworker/u8:6/981: 3, on CPU#0:
 #0: ffff88801c094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1466/0x1b10 kernel/workqueue.c:3362
 #1: ffffc90004e07d08 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3363
 #2: ffffffff90ccf180 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0x51/0xc0 net/core/link_watch.c:313
locks held by getty/5357: 2, on CPU#0:
 #0: ffff88803782d0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000321e2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
locks held by syz.3.355/6903: 3, on CPU#1:
 #0: ffff88802ce86470 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888057efc460 (sb_writers#16){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffffffff8f287680 (nfsd_mutex){+.+.}-{4:4}, at: write_ports+0xa5/0xcc0 fs/nfsd/nfsctl.c:867
locks held by syz.3.355/6909: 3, on CPU#1:
 #0: ffff88802dd9aef0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888057efc460 (sb_writers#16){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffffffff8f287680 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nrthreads+0x57/0xd0 fs/nfsd/nfssvc.c:252
locks held by kworker/0:7/9499: 3, on CPU#0:
 #0: ffff88801c0bed40 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x1466/0x1b10 kernel/workqueue.c:3362
 #1: ffffc900068dfd08 ((work_completion)(&(&ssp->srcu_sup->work)->work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3363
 #2: ffffffff8edeb428 (&ssp->srcu_sup->srcu_gp_mutex){+.+.}-{4:4}, at: srcu_advance_state kernel/rcu/srcutree.c:1794 [inline]
 #2: ffffffff8edeb428 (&ssp->srcu_sup->srcu_gp_mutex){+.+.}-{4:4}, at: process_srcu+0x77/0x20f0 kernel/rcu/srcutree.c:1954
locks held by kworker/0:8/9500: 4, on CPU#0:
 #0: ffff88801c0bed40 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x1466/0x1b10 kernel/workqueue.c:3362
 #1: ffffc9000693fd08 ((work_completion)(&(&ssp->srcu_sup->work)->work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3363
 #2: ffffffff8ef3c8e8 (&ssp->srcu_sup->srcu_gp_mutex){+.+.}-{4:4}, at: srcu_advance_state kernel/rcu/srcutree.c:1794 [inline]
 #2: ffffffff8ef3c8e8 (&ssp->srcu_sup->srcu_gp_mutex){+.+.}-{4:4}, at: process_srcu+0x77/0x20f0 kernel/rcu/srcutree.c:1954
 #3: ffffffff8edf7f68 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
locks held by syz.4.1601/11029: 2, on CPU#1:
 #0: ffffffff90ccf180 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #0: ffffffff90ccf180 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:134 [inline]
 #0: ffffffff90ccf180 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_dellink+0x307/0xb40 net/core/rtnetlink.c:3686
 #1: ffffffff8edf7f68 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
locks held by syz.1.1602/11034: 1, last CPU#0:
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock_dont_migrate include/linux/rcupdate.h:991 [inline]
 #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: bpf_test_timer_enter+0xc3/0x2c0 net/bpf/test_run.c:39
locks held by syz.9.1603/11039: 2, last CPU#1:
 #0: ffff888035701078 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:600 [inline]
 #0: ffff888035701078 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x124/0xa00 mm/mmap.c:1299
 #1: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x2f/0x310 mm/pgtable-generic.c:290
locks held by dhcpcd-run-hook/11043: 2, last CPU#1:
 #0: ffff888035705038 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:544 [inline]
 #0: ffff888035705038 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x22c/0xa00 mm/mmap.c:1323
 #1: ffff888036ce1848 (&mapping->i_mmap_rwsem){++++}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:507 [inline]
 #1: ffff888036ce1848 (&mapping->i_mmap_rwsem){++++}-{4:4}, at: unlink_file_vma_batch_process+0xef/0x500 mm/vma.c:1880

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:123
 nmi_trigger_cpumask_backtrace+0x21f/0x2a0 lib/nmi_backtrace.c:66
 trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xcb1/0x1030 kernel/hung_task.c:561
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 16 Comm: pr/ttyS0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:io_serial_in+0x87/0xb0 drivers/tty/serial/8250/8250_port.c:410
Code: 24 5c fc 48 8d 7d 40 44 89 e1 48 b8 00 00 00 00 00 fc ff df 48 89 fa d3 e3 48 c1 ea 03 80 3c 02 00 75 1a 66 03 5d 40 89 da ec <5b> 0f b6 c0 5d 41 5c c3 cc cc cc cc e8 c8 37 cf fc eb a2 e8 51 38
RSP: 0018:ffffc90000157958 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: ffffffff85afc750 RDI: ffffffff9bc60ca0
RBP: ffffffff9bc60c60 R08: 0000000000000001 R09: 000000000000001f
R10: 0000000000000000 R11: 205d313354202020 R12: 0000000000000000
R13: 0000000000000020 R14: fffffbfff378c1e9 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888123b64000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33c20ff8 CR3: 0000000041bb0000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000001800
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:128 [inline]
 serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
 wait_for_lsr+0x13a/0x210 drivers/tty/serial/8250/8250_port.c:2013
 serial8250_fifo_wait_for_lsr_thre+0x5f/0xd0 drivers/tty/serial/8250/8250_port.c:3270
 __serial8250_console_fifo_write+0xa5/0x290 drivers/tty/serial/8250/8250_port.c:3345
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3378 [inline]
 __serial8250_console_write drivers/tty/serial/8250/8250_port.c:3429 [inline]
 serial8250_console_write+0xf46/0x1330 drivers/tty/serial/8250/8250_port.c:3493
 nbcon_emit_next_record+0x8f7/0xa70 kernel/printk/nbcon.c:1070
 nbcon_emit_one+0x1a8/0x2b0 kernel/printk/nbcon.c:1157
 nbcon_kthread_func+0x613/0x7d0 kernel/printk/nbcon.c:1271
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>