syzbot

============================================
WARNING: possible recursive locking detected
syzkaller #0 Tainted: G             L     
--------------------------------------------
syz.1.16517/7823 is trying to acquire lock:
ffff88802f565128 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_do_insn+0x38/0x3c0 drivers/comedi/kcomedilib/kcomedilib_main.c:183

but task is already holding lock:
ffff88802f563928 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_unlocked_ioctl+0x14c/0x1020 drivers/comedi/comedi_fops.c:2228

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

       CPU0
       ----
  lock(&dev->mutex#4);
  lock(&dev->mutex#4);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz.1.16517/7823:
 #0: ffff88802f563928 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_unlocked_ioctl+0x14c/0x1020 drivers/comedi/comedi_fops.c:2228

stack backtrace:
CPU: 1 UID: 0 PID: 7823 Comm: syz.1.16517 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x2540/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
 comedi_do_insn+0x38/0x3c0 drivers/comedi/kcomedilib/kcomedilib_main.c:183
 comedi_dio_bitfield2+0x2d6/0x3b0 drivers/comedi/kcomedilib/kcomedilib_main.c:314
 bonding_dio_insn_bits+0x2a5/0x590 drivers/comedi/drivers/comedi_bond.c:100
 insn_rw_emulate_bits+0x34d/0x5f0 drivers/comedi/drivers.c:703
 parse_insn+0xa23/0x1b30 drivers/comedi/comedi_fops.c:1510
 do_insn_ioctl+0x174/0x5a0 drivers/comedi/comedi_fops.c:1735
 comedi_unlocked_ioctl+0x90d/0x1020 drivers/comedi/comedi_fops.c:2365
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8487c0f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8485e76038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8487e65fa0 RCX: 00007f8487c0f749
RDX: 0000200000000000 RSI: 000000008028640c RDI: 0000000000000003
RBP: 00007f8487c93f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8487e66038 R14: 00007f8487e65fa0 R15: 00007ffc446d2ec8
 </TASK>