digi_2 ttyUSB0: digi_write_oob_command: usb_submit_urb failed, ret=-19
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.2.7/4286 is trying to acquire lock:
ffff888078766818 (&priv->dp_port_lock){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
ffff888078766818 (&priv->dp_port_lock){..-.}-{2:2}, at: digi_set_modem_signals+0x1a1/0x860 drivers/usb/serial/digi_acceleport.c:528

but task is already holding lock:
ffff88802bd00418 (&priv->dp_port_lock){..-.}-{2:2}, at: digi_set_modem_signals+0x194/0x860 drivers/usb/serial/digi_acceleport.c:527

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

       CPU0
       ----
  lock(&priv->dp_port_lock);
  lock(&priv->dp_port_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz.2.7/4286:
 #0: ffff8880212351c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_init_dev+0x6f/0x470 drivers/tty/tty_io.c:1430
 #1: ffff88802bd00418 (&priv->dp_port_lock){..-.}-{2:2}, at: digi_set_modem_signals+0x194/0x860 drivers/usb/serial/digi_acceleport.c:527

stack backtrace:
CPU: 0 PID: 4286 Comm: syz.2.7 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 __lock_acquire+0x1247/0x7b50 kernel/locking/lockdep.c:-1
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:364 [inline]
 digi_set_modem_signals+0x1a1/0x860 drivers/usb/serial/digi_acceleport.c:528
 tty_port_raise_dtr_rts drivers/tty/tty_port.c:420 [inline]
 tty_port_block_til_ready+0x375/0x8b0 drivers/tty/tty_port.c:504
 tty_open+0x485/0xcd0 drivers/tty/tty_io.c:2165
 chrdev_open+0x585/0x5f0 fs/char_dev.c:414
 do_dentry_open+0x7f7/0xf90 fs/open.c:826
 do_open fs/namei.c:3616 [inline]
 path_openat+0x2718/0x2fb0 fs/namei.c:3750
 do_filp_open+0x1df/0x400 fs/namei.c:3777
 do_sys_openat2+0x14b/0x500 fs/open.c:1255
 do_sys_open fs/open.c:1271 [inline]
 __do_sys_openat fs/open.c:1287 [inline]
 __se_sys_openat fs/open.c:1282 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1282
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa7345510d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa7327a9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fa7347d8fa0 RCX: 00007fa7345510d9
RDX: 0000000000000002 RSI: 0000200000000700 RDI: ffffffffffffff9c
RBP: 00007fa7345e8024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa7347d9038 R14: 00007fa7347d8fa0 R15: 00007ffce18e2f78
 </TASK>
digi_2 ttyUSB0: digi_set_modem_signals: usb_submit_urb failed, ret=-19