gh-155811: Add a seqcount to gc_stats to prevent torn reads - #155828

import subprocess
import sys
import time

import _remote_debugging

target = """
import gc
import os
import time

print(os.getpid(), flush=True)
while True:
    gc.collect(0)
    time.sleep(0.01)
"""

p = subprocess.Popen(
    [sys.executable, "-c", target],
    stdout=subprocess.PIPE,
    text=True,
)
try:
    pid = int(p.stdout.readline())
    monitor = _remote_debugging.GCMonitor(pid, debug=True)
    successes = 0
    failures = 0
    messages = set()
    deadline = time.monotonic() + 10.0
    while time.monotonic() < deadline:
        try:
            monitor.get_gc_stats(all_interpreters=False)
            successes += 1
        except RuntimeError as exc:
            failures += 1
            messages.add(str(exc))
    print(f"successes={successes} failures={failures}")
    for message in sorted(messages):
        print(message)
finally:
    p.terminate()
    p.wait()