syzbot

=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
6.16.0-rc3-syzkaller #0 Not tainted
-----------------------------------------------------
kworker/u8:11/4490 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffffffff8f79b258 (disc_data_lock){.+.+}-{3:3}, at: sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370

and this task is already holding:
ffffffff9b073518 (&port_lock_key){-.-.}-{3:3}, at: uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
ffffffff9b073518 (&port_lock_key){-.-.}-{3:3}, at: uart_port_ref_lock drivers/tty/serial/serial_core.c:83 [inline]
ffffffff9b073518 (&port_lock_key){-.-.}-{3:3}, at: uart_write+0x13b/0xb30 drivers/tty/serial/serial_core.c:627
which would create a new lock dependency:
 (&port_lock_key){-.-.}-{3:3} -> (disc_data_lock){.+.+}-{3:3}

but this new dependency connects a HARDIRQ-irq-safe lock:
 (&port_lock_key){-.-.}-{3:3}

... which became HARDIRQ-irq-safe at:
  lock_acquire kernel/locking/lockdep.c:5871 [inline]
  lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
  uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
  serial8250_handle_irq+0x95/0xcb0 drivers/tty/serial/8250/8250_port.c:1917
  serial8250_default_handle_irq+0x9a/0x210 drivers/tty/serial/8250/8250_port.c:1966
  serial8250_interrupt+0x106/0x210 drivers/tty/serial/8250/8250_core.c:86
  __handle_irq_event_percpu+0x22c/0x7d0 kernel/irq/handle.c:158
  handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
  handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:210
  handle_edge_irq+0x28e/0xab0 kernel/irq/chip.c:797
  generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
  handle_irq arch/x86/kernel/irq.c:254 [inline]
  call_irq_handler arch/x86/kernel/irq.c:266 [inline]
  __common_interrupt+0xe2/0x250 arch/x86/kernel/irq.c:292
  common_interrupt+0xba/0xe0 arch/x86/kernel/irq.c:285
  asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
  native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
  pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:81
  arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
  default_idle+0x13/0x20 arch/x86/kernel/process.c:749
  default_idle_call+0x6d/0xb0 kernel/sched/idle.c:117
  cpuidle_idle_call kernel/sched/idle.c:185 [inline]
  do_idle+0x391/0x510 kernel/sched/idle.c:325
  cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:423
  start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:315
  common_startup_64+0x13e/0x148

to a HARDIRQ-irq-unsafe lock:
 (disc_data_lock){.+.+}-{3:3}

... which became HARDIRQ-irq-unsafe at:
...
  lock_acquire kernel/locking/lockdep.c:5871 [inline]
  lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
  __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
  _raw_read_lock+0x5f/0x70 kernel/locking/spinlock.c:228
  sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370
  sixpack_write_wakeup+0x20/0x390 drivers/net/hamradio/6pack.c:391
  tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
  tty_port_default_wakeup+0x2a/0x40 drivers/tty/tty_port.c:69
  uart_flush_buffer+0x37f/0x8a0 drivers/tty/serial/serial_core.c:689
  tty_driver_flush_buffer+0x64/0x80 drivers/tty/tty_ioctl.c:85
  tty_ldisc_hangup+0xe7/0x730 drivers/tty/tty_ldisc.c:700
  __tty_hangup.part.0+0x3d2/0x890 drivers/tty/tty_io.c:621
  __tty_hangup drivers/tty/tty_io.c:688 [inline]
  tty_vhangup drivers/tty/tty_io.c:691 [inline]
  tty_vhangup drivers/tty/tty_io.c:688 [inline]
  tty_ioctl+0x102d/0x1640 drivers/tty/tty_io.c:2732
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:907 [inline]
  __se_sys_ioctl fs/ioctl.c:893 [inline]
  __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
  do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(disc_data_lock);
                               local_irq_disable();
                               lock(&port_lock_key);
                               lock(disc_data_lock);
  <Interrupt>
    lock(&port_lock_key);

 *** DEADLOCK ***

6 locks held by kworker/u8:11/4490:
 #0: ffff88801b881148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc9000dcb7d10 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffff8880257e8ca0 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x780 drivers/tty/tty_buffer.c:467
 #3: ffff88807f92e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1c/0x80 drivers/tty/tty_ldisc.c:263
 #4: ffffffff9b073518 (&port_lock_key){-.-.}-{3:3}, at: uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
 #4: ffffffff9b073518 (&port_lock_key){-.-.}-{3:3}, at: uart_port_ref_lock drivers/tty/serial/serial_core.c:83 [inline]
 #4: ffffffff9b073518 (&port_lock_key){-.-.}-{3:3}, at: uart_write+0x13b/0xb30 drivers/tty/serial/serial_core.c:627
 #5: ffff88807f92e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1c/0x80 drivers/tty/tty_ldisc.c:263

the dependencies between HARDIRQ-irq-safe lock and the holding lock:
-> (&port_lock_key){-.-.}-{3:3} {
   IN-HARDIRQ-W at:
                    lock_acquire kernel/locking/lockdep.c:5871 [inline]
                    lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                    _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
                    uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
                    serial8250_handle_irq+0x95/0xcb0 drivers/tty/serial/8250/8250_port.c:1917
                    serial8250_default_handle_irq+0x9a/0x210 drivers/tty/serial/8250/8250_port.c:1966
                    serial8250_interrupt+0x106/0x210 drivers/tty/serial/8250/8250_core.c:86
                    __handle_irq_event_percpu+0x22c/0x7d0 kernel/irq/handle.c:158
                    handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
                    handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:210
                    handle_edge_irq+0x28e/0xab0 kernel/irq/chip.c:797
                    generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
                    handle_irq arch/x86/kernel/irq.c:254 [inline]
                    call_irq_handler arch/x86/kernel/irq.c:266 [inline]
                    __common_interrupt+0xe2/0x250 arch/x86/kernel/irq.c:292
                    common_interrupt+0xba/0xe0 arch/x86/kernel/irq.c:285
                    asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
                    native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
                    pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:81
                    arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
                    default_idle+0x13/0x20 arch/x86/kernel/process.c:749
                    default_idle_call+0x6d/0xb0 kernel/sched/idle.c:117
                    cpuidle_idle_call kernel/sched/idle.c:185 [inline]
                    do_idle+0x391/0x510 kernel/sched/idle.c:325
                    cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:423
                    start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:315
                    common_startup_64+0x13e/0x148
   IN-SOFTIRQ-W at:
                    lock_acquire kernel/locking/lockdep.c:5871 [inline]
                    lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                    _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
                    uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
                    serial8250_handle_irq+0x95/0xcb0 drivers/tty/serial/8250/8250_port.c:1917
                    serial8250_default_handle_irq+0x9a/0x210 drivers/tty/serial/8250/8250_port.c:1966
                    serial8250_interrupt+0x106/0x210 drivers/tty/serial/8250/8250_core.c:86
                    __handle_irq_event_percpu+0x22c/0x7d0 kernel/irq/handle.c:158
                    handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
                    handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:210
                    handle_edge_irq+0x28e/0xab0 kernel/irq/chip.c:797
                    generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
                    handle_irq arch/x86/kernel/irq.c:254 [inline]
                    call_irq_handler arch/x86/kernel/irq.c:266 [inline]
                    __common_interrupt+0xe2/0x250 arch/x86/kernel/irq.c:292
                    common_interrupt+0x61/0xe0 arch/x86/kernel/irq.c:285
                    asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
                    variable_ffs arch/x86/include/asm/bitops.h:318 [inline]
                    handle_softirqs+0x1dd/0x8e0 kernel/softirq.c:567
                    __do_softirq kernel/softirq.c:613 [inline]
                    invoke_softirq kernel/softirq.c:453 [inline]
                    __irq_exit_rcu+0x109/0x170 kernel/softirq.c:680
                    irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
                    instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
                    sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1050
                    asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
                    lock_acquire+0x62/0x350 kernel/locking/lockdep.c:5836
                    rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
                    rcu_read_lock include/linux/rcupdate.h:841 [inline]
                    ___pte_offset_map+0x48/0x570 mm/pgtable-generic.c:287
                    __pte_offset_map include/linux/mm.h:2995 [inline]
                    __pte_offset_map_lock+0x8d/0x310 mm/pgtable-generic.c:398
                    pte_offset_map_lock include/linux/mm.h:3010 [inline]
                    zap_pte_range mm/memory.c:1721 [inline]
                    zap_pmd_range mm/memory.c:1827 [inline]
                    zap_pud_range mm/memory.c:1856 [inline]
                    zap_p4d_range mm/memory.c:1877 [inline]
                    unmap_page_range+0xbc3/0x4350 mm/memory.c:1898
                    unmap_single_vma.constprop.0+0x153/0x240 mm/memory.c:1941
                    unmap_vmas+0x218/0x470 mm/memory.c:1985
                    exit_mmap+0x1b9/0xb90 mm/mmap.c:1284
                    __mmput+0x12a/0x410 kernel/fork.c:1121
                    mmput+0x62/0x70 kernel/fork.c:1144
                    exit_mm kernel/exit.c:581 [inline]
                    do_exit+0x7c4/0x2bd0 kernel/exit.c:952
                    do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
                    __do_sys_exit_group kernel/exit.c:1116 [inline]
                    __se_sys_exit_group kernel/exit.c:1114 [inline]
                    __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
                    x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
                    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                    do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
                    entry_SYSCALL_64_after_hwframe+0x77/0x7f
   INITIAL USE at:
                   lock_acquire kernel/locking/lockdep.c:5871 [inline]
                   lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                   _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
                   uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
                   serial8250_do_set_termios+0x310/0x1710 drivers/tty/serial/8250/8250_port.c:2774
                   serial8250_set_termios+0x6e/0x80 drivers/tty/serial/8250/8250_port.c:2899
                   uart_set_options+0x31a/0x5f0 drivers/tty/serial/serial_core.c:2309
                   serial8250_console_setup+0x189/0x450 drivers/tty/serial/8250/8250_port.c:3519
                   univ8250_console_setup+0x1eb/0x2e0 drivers/tty/serial/8250/8250_core.c:428
                   console_call_setup kernel/printk/printk.c:3799 [inline]
                   console_call_setup kernel/printk/printk.c:3790 [inline]
                   try_enable_preferred_console+0x2fd/0x530 kernel/printk/printk.c:3843
                   register_console+0x3ab/0x11b0 kernel/printk/printk.c:4037
                   univ8250_console_init+0x5f/0x90 drivers/tty/serial/8250/8250_core.c:513
                   console_init+0x14f/0x680 kernel/printk/printk.c:4323
                   start_kernel+0x29f/0x4d0 init/main.c:1036
                   x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:307
                   x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:288
                   common_startup_64+0x13e/0x148
 }
 ... key      at: [<ffffffff9b072780>] port_lock_key+0x0/0x40

the dependencies between the lock to be acquired
 and HARDIRQ-irq-unsafe lock:
-> (disc_data_lock){.+.+}-{3:3} {
   HARDIRQ-ON-R at:
                    lock_acquire kernel/locking/lockdep.c:5871 [inline]
                    lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                    __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
                    _raw_read_lock+0x5f/0x70 kernel/locking/spinlock.c:228
                    sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370
                    sixpack_write_wakeup+0x20/0x390 drivers/net/hamradio/6pack.c:391
                    tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
                    tty_port_default_wakeup+0x2a/0x40 drivers/tty/tty_port.c:69
                    uart_flush_buffer+0x37f/0x8a0 drivers/tty/serial/serial_core.c:689
                    tty_driver_flush_buffer+0x64/0x80 drivers/tty/tty_ioctl.c:85
                    tty_ldisc_hangup+0xe7/0x730 drivers/tty/tty_ldisc.c:700
                    __tty_hangup.part.0+0x3d2/0x890 drivers/tty/tty_io.c:621
                    __tty_hangup drivers/tty/tty_io.c:688 [inline]
                    tty_vhangup drivers/tty/tty_io.c:691 [inline]
                    tty_vhangup drivers/tty/tty_io.c:688 [inline]
                    tty_ioctl+0x102d/0x1640 drivers/tty/tty_io.c:2732
                    vfs_ioctl fs/ioctl.c:51 [inline]
                    __do_sys_ioctl fs/ioctl.c:907 [inline]
                    __se_sys_ioctl fs/ioctl.c:893 [inline]
                    __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
                    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                    do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
                    entry_SYSCALL_64_after_hwframe+0x77/0x7f
   SOFTIRQ-ON-R at:
                    lock_acquire kernel/locking/lockdep.c:5871 [inline]
                    lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                    __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
                    _raw_read_lock+0x5f/0x70 kernel/locking/spinlock.c:228
                    sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370
                    sixpack_write_wakeup+0x20/0x390 drivers/net/hamradio/6pack.c:391
                    tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
                    tty_port_default_wakeup+0x2a/0x40 drivers/tty/tty_port.c:69
                    uart_flush_buffer+0x37f/0x8a0 drivers/tty/serial/serial_core.c:689
                    tty_driver_flush_buffer+0x64/0x80 drivers/tty/tty_ioctl.c:85
                    tty_ldisc_hangup+0xe7/0x730 drivers/tty/tty_ldisc.c:700
                    __tty_hangup.part.0+0x3d2/0x890 drivers/tty/tty_io.c:621
                    __tty_hangup drivers/tty/tty_io.c:688 [inline]
                    tty_vhangup drivers/tty/tty_io.c:691 [inline]
                    tty_vhangup drivers/tty/tty_io.c:688 [inline]
                    tty_ioctl+0x102d/0x1640 drivers/tty/tty_io.c:2732
                    vfs_ioctl fs/ioctl.c:51 [inline]
                    __do_sys_ioctl fs/ioctl.c:907 [inline]
                    __se_sys_ioctl fs/ioctl.c:893 [inline]
                    __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
                    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                    do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
                    entry_SYSCALL_64_after_hwframe+0x77/0x7f
   INITIAL USE at:
                   lock_acquire kernel/locking/lockdep.c:5871 [inline]
                   lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                   __raw_write_lock_irq include/linux/rwlock_api_smp.h:195 [inline]
                   _raw_write_lock_irq+0x36/0x50 kernel/locking/spinlock.c:326
                   sixpack_close+0x1e/0x2f0 drivers/net/hamradio/6pack.c:641
                   tty_ldisc_close+0x114/0x1a0 drivers/tty/tty_ldisc.c:455
                   tty_ldisc_kill+0x8e/0x150 drivers/tty/tty_ldisc.c:613
                   tty_ldisc_hangup+0x365/0x730 drivers/tty/tty_ldisc.c:729
                   __tty_hangup.part.0+0x3d2/0x890 drivers/tty/tty_io.c:621
                   __tty_hangup drivers/tty/tty_io.c:688 [inline]
                   tty_vhangup drivers/tty/tty_io.c:691 [inline]
                   tty_vhangup drivers/tty/tty_io.c:688 [inline]
                   tty_ioctl+0x102d/0x1640 drivers/tty/tty_io.c:2732
                   vfs_ioctl fs/ioctl.c:51 [inline]
                   __do_sys_ioctl fs/ioctl.c:907 [inline]
                   __se_sys_ioctl fs/ioctl.c:893 [inline]
                   __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
                   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                   do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
                   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   INITIAL READ USE at:
                        lock_acquire kernel/locking/lockdep.c:5871 [inline]
                        lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
                        __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
                        _raw_read_lock+0x5f/0x70 kernel/locking/spinlock.c:228
                        sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370
                        sixpack_write_wakeup+0x20/0x390 drivers/net/hamradio/6pack.c:391
                        tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
                        tty_port_default_wakeup+0x2a/0x40 drivers/tty/tty_port.c:69
                        uart_flush_buffer+0x37f/0x8a0 drivers/tty/serial/serial_core.c:689
                        tty_driver_flush_buffer+0x64/0x80 drivers/tty/tty_ioctl.c:85
                        tty_ldisc_hangup+0xe7/0x730 drivers/tty/tty_ldisc.c:700
                        __tty_hangup.part.0+0x3d2/0x890 drivers/tty/tty_io.c:621
                        __tty_hangup drivers/tty/tty_io.c:688 [inline]
                        tty_vhangup drivers/tty/tty_io.c:691 [inline]
                        tty_vhangup drivers/tty/tty_io.c:688 [inline]
                        tty_ioctl+0x102d/0x1640 drivers/tty/tty_io.c:2732
                        vfs_ioctl fs/ioctl.c:51 [inline]
                        __do_sys_ioctl fs/ioctl.c:907 [inline]
                        __se_sys_ioctl fs/ioctl.c:893 [inline]
                        __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
                        do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                        do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
                        entry_SYSCALL_64_after_hwframe+0x77/0x7f
 }
 ... key      at: [<ffffffff8f79b258>] disc_data_lock+0x18/0xfe0 6pack.c:-1
 ... acquired at:
   lock_acquire kernel/locking/lockdep.c:5871 [inline]
   lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
   __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
   _raw_read_lock+0x5f/0x70 kernel/locking/spinlock.c:228
   sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370
   sixpack_write_wakeup+0x20/0x390 drivers/net/hamradio/6pack.c:391
   tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
   tty_port_default_wakeup+0x2a/0x40 drivers/tty/tty_port.c:69
   serial8250_tx_chars+0x68e/0x860 drivers/tty/serial/8250/8250_port.c:1838
   __start_tx+0x3e9/0x4a0 drivers/tty/serial/8250/8250_port.c:1543
   serial8250_start_tx+0x368/0x530 drivers/tty/serial/8250/8250_port.c:1653
   __uart_start+0x295/0x4c0 drivers/tty/serial/serial_core.c:161
   uart_write+0x218/0xb30 drivers/tty/serial/serial_core.c:636
   decode_prio_command drivers/net/hamradio/6pack.c:868 [inline]
   sixpack_decode drivers/net/hamradio/6pack.c:943 [inline]
   sixpack_receive_buf drivers/net/hamradio/6pack.c:447 [inline]
   sixpack_receive_buf+0x3d3/0x1c90 drivers/net/hamradio/6pack.c:424
   tty_ldisc_receive_buf+0x15a/0x1a0 drivers/tty/tty_buffer.c:391
   tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
   receive_buf drivers/tty/tty_buffer.c:445 [inline]
   flush_to_ldisc+0x26b/0x780 drivers/tty/tty_buffer.c:495
   process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
   process_scheduled_works kernel/workqueue.c:3321 [inline]
   worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
   kthread+0x3c5/0x780 kernel/kthread.c:464
   ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245


stack backtrace:
CPU: 1 UID: 0 PID: 4490 Comm: kworker/u8:11 Not tainted 6.16.0-rc3-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_bad_irq_dependency kernel/locking/lockdep.c:2619 [inline]
 check_irq_usage+0x7dc/0x920 kernel/locking/lockdep.c:2860
 check_prev_add kernel/locking/lockdep.c:3172 [inline]
 check_prevs_add kernel/locking/lockdep.c:3287 [inline]
 validate_chain kernel/locking/lockdep.c:3911 [inline]
 __lock_acquire+0x1285/0x1c90 kernel/locking/lockdep.c:5240
 lock_acquire kernel/locking/lockdep.c:5871 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
 __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
 _raw_read_lock+0x5f/0x70 kernel/locking/spinlock.c:228
 sp_get+0x18/0xf0 drivers/net/hamradio/6pack.c:370
 sixpack_write_wakeup+0x20/0x390 drivers/net/hamradio/6pack.c:391
 tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
 tty_port_default_wakeup+0x2a/0x40 drivers/tty/tty_port.c:69
 serial8250_tx_chars+0x68e/0x860 drivers/tty/serial/8250/8250_port.c:1838
 __start_tx+0x3e9/0x4a0 drivers/tty/serial/8250/8250_port.c:1543
 serial8250_start_tx+0x368/0x530 drivers/tty/serial/8250/8250_port.c:1653
 __uart_start+0x295/0x4c0 drivers/tty/serial/serial_core.c:161
 uart_write+0x218/0xb30 drivers/tty/serial/serial_core.c:636
 decode_prio_command drivers/net/hamradio/6pack.c:868 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:943 [inline]
 sixpack_receive_buf drivers/net/hamradio/6pack.c:447 [inline]
 sixpack_receive_buf+0x3d3/0x1c90 drivers/net/hamradio/6pack.c:424
 tty_ldisc_receive_buf+0x15a/0x1a0 drivers/tty/tty_buffer.c:391
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x26b/0x780 drivers/tty/tty_buffer.c:495
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c5/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>