[Python] Running two functions in their own processes and terminating one

I have a setup to run a render and measure the workload on the GPU in Python, using two functions that I run independently using the multiprocessing module to launch them. However, I need to terminate one from the other, so I store the object returned by subprocess.popen() globally to terminate it:

import os
import multiprocessing
import subprocess

nvidia_cmd = None

blender_cmd_to_run = '/home/mickey/dev/blender-4.2.1-linux-x64/blender -b /home/mickey/dev/elastic_shared_memory/benchmark_scenes/bmw27/bmw27.blend -f 10 -- --cycles-device CUDA'
nvidia_cmd_to_run = 'nvidia-smi --query-gpu=gpu_bus_id,memory.used --format=csv -l 1'

def run_blender():
blender_cmd = subprocess.Popen(blender_cmd_to_run, shell=True, stdout=subprocess.PIPE)
for line in blender_cmd.stdout:
print(line.decode().strip())
nvidia_cmd.terminate()

def run_nvidia():
global nvidia_cmd
nvidia_cmd = subprocess.Popen(nvidia_cmd_to_run, shell=True, stdout=subprocess.PIPE)
for line in nvidia_cmd.stdout:
print(line.decode().strip())


if __name__ == '__main__':
blender_process = multiprocessing.Process(target=run_blender)
nvidia_process = multiprocessing.Process(target=run_nvidia)

nvidia_process.start()
blender_process.start()


However, when the blender_process function ends, I get an error with the terminate call:

AttributeError: 'NoneType' object has no attribute 'terminate'


But why? I'm storing the value as soon as the other command is launched. What am I missing?

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