"""Linux spawn/environment race. Use --no-environment-updates as a control."""

from collections import Counter
from concurrent.futures import ThreadPoolExecutor
import multiprocessing as mp
import os
import sys
import threading
import time

def child():
    pass


def update_environment(stop):
    keys = [f"SPAWN_REPRO_{i}" for i in range(256)]
    while not stop.is_set():
        for key in keys:
            os.environ[key] = "test"
        for key in keys:
            os.environ.pop(key, None)
        time.sleep(0)


def start_process(_):
    process = mp.get_context("spawn").Process(target=child)
    try:
        process.start()
    except Exception as error:
        process.close()
        return error
    return process


if __name__ == "__main__":
    print(sys.version, flush=True)
    # Start the resource tracker before racing, using only the public API.
    warmup = mp.get_context("spawn").Process(target=child)
    warmup.start()
    warmup.join()
    warmup.close()

    stop = threading.Event()
    updater = threading.Thread(target=update_environment, args=(stop,))
    if "--no-environment-updates" not in sys.argv:
        updater.start()
    try:
        with ThreadPoolExecutor(32) as executor:
            for round_number in range(20):
                # Finish all starts before joining: avoid concurrent reaping.
                results = list(executor.map(start_process, range(32)))
                counts = Counter()
                for result in results:
                    if isinstance(result, Exception):
                        counts[repr(result)] += 1
                    else:
                        result.join()
                        counts[result.exitcode] += 1
                        result.close()
                print(f"round {round_number + 1}: {dict(counts)}", flush=True)
                if counts[0] != 32:
                    raise SystemExit(1)
    finally:
        stop.set()
        if updater.ident is not None:
            updater.join()