What the meaning of `exitcode -6`

I was training a Yolo model with DDP, and got DDP error with messages below:

[1]:
  time      : 2024-04-17_15:48:22
  host      : mccx6
  rank      : 4 (local_rank: 4)
  exitcode  : -6 (pid: 3882833)
  error_file: <N/A>
  traceback : Signal 6 (SIGABRT) received by PID 3882833
[2]:
  time      : 2024-04-17_15:48:22
  host      : mccx6
  rank      : 6 (local_rank: 6)
  exitcode  : -6 (pid: 3882835)
  error_file: <N/A>
  traceback : Signal 6 (SIGABRT) received by PID 3882835
--------------------------------------------------------
Root Cause (first observed failure):
[0]:
  time      : 2024-04-17_15:48:22
  host      : mccx6
  rank      : 2 (local_rank: 2)
  exitcode  : -6 (pid: 3882831)
  error_file: <N/A>
  traceback : Signal 6 (SIGABRT) received by PID 3882831
=======================================================

It usally happened at the end of an epoch, and I don’t know what the exitcode -6 means.