Why does multiprocessing only works with fork?


I was experimenting with some multiprocessing in an Omniverse extension. I can start basic processes and communicate back with Omniverse using queues and coroutine which is great. Now I want to do some pointcloud processing in the background using open3d, the thing with open3d is that it will not work properly when using multiprocessing if the start method is set to “fork” but will work perfectly using “forkserver”. However, when I can’t start any process in Omniverse unless I am using fork… is there a reason this happens and is there any work around ?

See this basic extension to replicate the issue (just change forkserver to fork and everything works)

import omni.ext
import omni.ui as ui
import omni.kit.app
import multiprocessing as mp
import time
import logging
import asyncio
import queue

logger = logging.getLogger(__name__)

def do_some_processing(cb_queue):
    for i in range(5):
        cb_queue.put(f"Proccessed {i}")

async def poll_queue(cb_queue):
    while True:
            message = cb_queue.get_nowait()
            if message is None:
        except queue.Empty:
            await asyncio.sleep(1)

class TechofficeAnthonyPgExtension(omni.ext.IExt):
    def on_startup(self, ext_id):
        # OTHER CODE
        ctx = mp.get_context("forkserver")
        self.q = ctx.Queue()
        self.poller = None

        # UI CODE
        self._window = ui.Window("My Window", width=300, height=300)
        with self._window.frame:
            def btn_fn():
                process = ctx.Process(target=do_some_processing, args=(self.q, ))
                self.poller = asyncio.ensure_future(poll_queue(self.q))
            with ui.VStack():
                with ui.HStack():
                    ui.Button("Start process", clicked_fn=btn_fn)

    def on_shutdown(self):
        if self.poller: