gh-145446: Add critical section in functools module for `PyDict_Next` by brijkapadia · Pull Request #145487 · python/cpython

@colesbury After further reflection, I actually think that you need the critical section in the remaining cases. For example, without the critical section, this code results in a data race:

from functools import partial 
from threading import Thread

p = partial(lambda: None)

def f():
    for _ in range(100):
        repr(p)

def g():
    for i in range(100):
        p.keywords[f"{i}"] = i


t1 = Thread(target=f)
t2 = Thread(target=g)

t1.start()
t2.start()

t1.join()
t2.join()

I attached the full TSan report here although it is quite long and I don't think it is that illuminating.

However, the only remaining cases are for the kw entry of the partial object. As such, a better solution might be to transition this kw dict to a frozendict (see issue #145478).

Let me know if you think it is worth continuing this PR or if we should close it.