============================================
WARNING: possible recursive locking detected
5.16.0-rc3-syzkaller #0 Not tainted
--------------------------------------------
syz-fuzzer/6520 is trying to acquire lock:
ffffffff90f553f0 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0xfe/0x920 drivers/tty/serial/serial_core.c:577

but task is already holding lock:
ffffffff90f553f0 (&port_lock_key){-.-.}-{2:2}, at: serial8250_handle_irq+0x3f/0x3e0 drivers/tty/serial/8250/8250_port.c:1908

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&port_lock_key);
  lock(&port_lock_key);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by syz-fuzzer/6520:
 #0: ffff88806fc9cc30 (&i->lock){-.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline]
 #0: ffff88806fc9cc30 (&i->lock){-.-.}-{2:2}, at: serial8250_interrupt+0x39/0x1e0 drivers/tty/serial/8250/8250_core.c:116
 #1: ffffffff90f553f0 (&port_lock_key){-.-.}-{2:2}, at: serial8250_handle_irq+0x3f/0x3e0 drivers/tty/serial/8250/8250_port.c:1908
 #2: ffff88806dd86098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:273

stack backtrace:
CPU: 1 PID: 6520 Comm: syz-fuzzer Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106
 print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
 check_deadlock kernel/locking/lockdep.c:2999 [inline]
 validate_chain+0x5984/0x8240 kernel/locking/lockdep.c:3788
 __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5027
 lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5637
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
 uart_write+0xfe/0x920 drivers/tty/serial/serial_core.c:577
 n_hdlc_send_frames+0x34e/0xb20 drivers/tty/n_hdlc.c:290
 tty_wakeup+0xb3/0xf0 drivers/tty/tty_io.c:534
 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:51
 serial8250_tx_chars+0x68e/0x8a0 drivers/tty/serial/8250/8250_port.c:1845
 serial8250_handle_irq+0x2fd/0x3e0 drivers/tty/serial/8250/8250_port.c:1932
 serial8250_default_handle_irq+0xaf/0x190 drivers/tty/serial/8250/8250_port.c:1949
 serial8250_interrupt+0xa3/0x1e0 drivers/tty/serial/8250/8250_core.c:126
 __handle_irq_event_percpu+0x20d/0x730 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:198 [inline]
 handle_irq_event+0x10a/0x300 kernel/irq/handle.c:215
 handle_edge_irq+0x245/0xbe0 kernel/irq/chip.c:822
 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
 handle_irq arch/x86/kernel/irq.c:231 [inline]
 __common_interrupt+0xce/0x1e0 arch/x86/kernel/irq.c:250
 common_interrupt+0x4a/0xc0 arch/x86/kernel/irq.c:240
 asm_common_interrupt+0x1e/0x40
RIP: 0033:0x420d80
Code: 48 0f 47 d7 48 89 54 24 50 31 c9 eb 07 49 8d 7b 08 48 89 f9 48 39 d1 0f 83 65 01 00 00 48 89 4c 24 58 48 85 c9 74 0e 0f 1f 00 <83> fe 03 0f 83 f9 00 00 00 ff c6 0f b6 3b 49 89 cb 89 f1 41 89 fc
RSP: 002b:000000c00023fea8 EFLAGS: 00000206
RAX: 0000000000203007 RBX: 00007f66f32f606d RCX: 0000000000000028
RDX: 0000000000000080 RSI: 0000000000000000 RDI: 0000000000000028
RBP: 000000c00023ff28 R08: 00007f66f33e6fff R09: 000000c01e1e0d80
R10: 000000c00001fe98 R11: 0000000000000020 R12: 00000000000000fa
R13: 000000c000001200 R14: 000000c02c5696e0 R15: 0000000000000000
 </TASK>