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Steps to reproduce:

>xcopy /I"%ProgramFiles%\Python310\Lib\multiprocessing" multiprocessing>type a.patch--- a/multiprocessing/connection.py+++ b/multiprocessing/connection.py@@ -282,6 +282,8 @@             _CloseHandle(self._handle)         def _send_bytes(self, buf):+            if (10, 1) in util._finalizer_registry:+                import gc; gc.collect()             ov, err = _winapi.WriteFile(self._handle, buf, overlapped=True)             try:                 if err == _winapi.ERROR_IO_PENDING:>patch -p1< a.patch>type a.py#!/usr/bin/env pythonimport multiprocessing as mpdef foo(lock, i):    def func(x):        # for circular reference        with lock:            pass        if x > 0:            return func(x - 1)    func(i)if __name__ == '__main__':    m = mp.Manager()    lock = m.Lock()    with mp.Pool(2) as pool:        for _ in pool.starmap(foo, ((lock, i) for i in range(10))):            pass>a.py

Most changes to Pythonrequire a NEWS entry.

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Like I mentioned here#71936 (comment), this patch resolves the problem I am running into on Python 3.12.3.

@hattya, could you add a news entry like the bot suggests? I see you already did that.

I just ran into this exact problem again in a slightly different context thanmy previous comment.

@encukou,@gpshead,@vstinner, and@AlexWaygood (most recent reviewers of this module – apologies for direct tag), would any of you be able to take a look at this?

This PR solves the race condition I keep running into. For example, seethis build of the documentation.

My review led to a “competing” PR:#124973
@basnijholt, could you check if that also solves the issue for you?

I have merged the PR that builds on this one.
Thank you for the fix,@hattya!

@encukou, I also replied in#71936 (comment) and it indeed solves my problem!

With this fix hopefully Readthedocs builds forhttps://github.com/pipefunc/pipefunc will not randomly fail now 👍