import sys, threading
from decimal import Decimal
assert not sys._is_gil_enabled(), "run free-threaded: PYTHON_GIL=0"

NT = 4
ROUNDS = 4000
pool = [None]
enter = threading.Barrier(NT + 1)
leave = threading.Barrier(NT + 1)

def worker():
    for _ in range(ROUNDS):
        enter.wait()
        for d in pool[0]:
            hash(d)                     # dec_hash: read self->hash==-1, then write it
        leave.wait()

ts = [threading.Thread(target=worker) for _ in range(NT)]
for t in ts: t.start()
for r in range(ROUNDS):
    pool[0] = [Decimal(f"{r}.{i}") for i in range(64)]   # fresh, unhashed each round
    enter.wait(); leave.wait()
for t in ts: t.join()
print("done, no crash")