不，就是确保父进程是单线程的，也就是说你要 fork 的那个进程里不能有多个线程。可以了解一下 fork safe 这个概念，fork 出来的子进程并不会继承父进程的所有线程，会造成一些问题。
为了解决这个问题，multiprocessing 给出了 spwan 跟 forkserver 两个启动子进程的方式，这里摘抄一点官方文档：
Depending on the platform, multiprocessing supports three ways to start a process. These start methods are
The parent process starts a fresh python interpreter process. The child process will only inherit those resources necessary to run the process objects run() method. In particular, unnecessary file descriptors and handles from the parent process will not be inherited. Starting a process using this method is rather slow compared to using fork or forkserver.
Available on Unix and Windows. The default on Windows and macOS.
The parent process uses os.fork() to fork the Python interpreter. The child process, when it begins, is effectively identical to the parent process. All resources of the parent are inherited by the child process. Note that safely forking a multithreaded process is problematic.
Available on Unix only. The default on Unix.
When the program starts and selects the forkserver start method, a server process is started. From then on, whenever a new process is needed, the parent process connects to the server and requests that it fork a new process. The fork server process is single threaded so it is safe for it to use os.fork(). No unnecessary resources are inherited.