Relevant issue: https://stackoverflow.com/a/65152341

pool_highmem_deadlock.py

import sys
import time
import logging
import multiprocessing as mp


def work(x):
    ys = []

    if x % 2 == 0:
        for i in range(10):
            y = bytearray(1024*1024*1024 * 1)
            ys.append(y)
            time.sleep(i)
        return len(ys)

    return 0

if __name__ == '__main__':
    logger = mp.get_logger()

    logger.setLevel(logging.DEBUG)
    formatter = logging.Formatter(
        fmt='[%(process)d] %(message)s',
        datefmt='%y-%m-%d %H:%M:%S')

    handler = logging.StreamHandler(sys.stdout)
    handler.setFormatter(formatter)
    logger.addHandler(handler)

    N = 16
    out = []
    with mp.Pool(processes=8, maxtasksperchild=1) as pool:
        for y in pool.imap_unordered(work, range(N)):
            out.append(y)
            logger.debug('%2d/%2d', len(out), N)

    print('done')
    print(out)