def start_proc_mask_signal(proc):
    """
    Start process(es) with SIGINT ignored.

    Args:
        proc: (mp.Process or list)

    Note:
        The signal mask is only applied when called from main thread.
    """
    if not isinstance(proc, list):
        proc = [proc]

    with mask_sigint():
        for p in proc:
            if isinstance(p, mp.Process):
                if sys.version_info < (3, 4) or mp.get_start_method() == 'fork':
                    log_once("""
Starting a process with 'fork' method is efficient but not safe and may cause deadlock or crash.
Use 'forkserver' or 'spawn' method instead if you run into such issues.
See https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods on how to set them.
""".replace("\n", ""),
'warn')  # noqa
            p.start()

    Start process(es) with SIGINT ignored.

    Args:
        proc: (mp.Process or list)

    Note:
        The signal mask is only applied when called from main thread.
    
tensorpack/utils/concurrency.py