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GeezerVison is showing github.com — gh-140431: Fix GC crash due to partially initialized coroutines by colesbury · Pull Request #140470 · python/cpython

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colesbury commented Oct 22, 2025 •

edited by bedevere-app Bot

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The make_gen() function creates and tracks generator/coro objects, but doesn't fully initialize all the fields. At a minimum, we need to initialize all the fields that may be accessed by gen_traverse because the call to compute_cr_origin() can trigger a GC.

Issue: Segfault in gc_free_threading.c after PR #140262 with ASAN build and free-threading tests #140431

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          pythongh-140431: Fix GC crash due to partially initialized coroutines

c1e2a6e

The `make_gen()` function creates and tracks generator/coro objects, but
doesn't fully initialize all the fields. At a minimum, we need to
initialize all the fields that may be accessed by gen_traverse because
the call to `compute_cr_origin()` can trigger a GC.

colesbury added the needs backport to 3.14 bugs and security fixes label

Oct 22, 2025

bedevere-app Bot mentioned this pull request

Oct 22, 2025

Segfault in gc_free_threading.c after PR #140262 with ASAN build and free-threading tests #140431

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colesbury marked this pull request as ready for review

October 22, 2025 17:59

colesbury requested a review from markshannon as a code owner

October 22, 2025 17:59

bedevere-app Bot added the awaiting core review label

Oct 22, 2025

colesbury requested a review from kumaraditya303

October 22, 2025 18:01

pgdr commented Oct 23, 2025 •

edited

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For what it's worth, with this patch, I am no longer able to reproduce the bug.

With this patch, I was not able to reproduce the bug after an hour of running the tests.

Without this patch, the segfault occurs on average after < 4 minutes.

I have used the following script to check:

Details

#!/usr/bin/env bash

set -e

time_start=$(date +%s)

git clean -dfx

CC=clang CXX=clang++ ./configure --with-address-sanitizer --with-pydebug --disable-gil

make -j12

./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading
./python -X dev -m test -R 9:9 test_asyncio.test_free_threading

time_end=$(date +%s)
delta=$((time_end - time_start))
minutes=$((delta / 60))
seconds=$((delta % 60))

echo
echo
echo "Elapsed time: ${minutes}m ${seconds}s"
echo
echo -n "Possibly good commit: "
git rev-parse HEAD
git log --oneline | head -n 1
echo

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efimov-mikhail approved these changes

Oct 23, 2025

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LGTM.

We definitely need to set correct value of gen->gi_iframe.f_executable in make_gen.

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kumaraditya303 approved these changes

Oct 23, 2025

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LGTM

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bedevere-app Bot added awaiting merge and removed awaiting core review labels

Oct 23, 2025

colesbury merged commit 574405c into python:main

Oct 23, 2025

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miss-islington-app Bot commented Oct 23, 2025

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Thanks @colesbury for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

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bedevere-app Bot removed the awaiting merge label

Oct 23, 2025

colesbury deleted the gh-140431-gen branch

October 23, 2025 14:18

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request

Oct 23, 2025


          pythongh-140431: Fix GC crash due to partially initialized coroutines (…

fa8895b

…pythongh-140470)

The `make_gen()` function creates and tracks generator/coro objects, but
doesn't fully initialize all the fields. At a minimum, we need to
initialize all the fields that may be accessed by gen_traverse because
the call to `compute_cr_origin()` can trigger a GC.
(cherry picked from commit 574405c)

Co-authored-by: Sam Gross <[email protected]>

bedevere-app Bot commented Oct 23, 2025

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GH-140504 is a backport of this pull request to the 3.14 branch.

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bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label

Oct 23, 2025

bedevere-bot commented Oct 23, 2025

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⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 macOS 3.x (tier-2) has failed when building commit 574405c.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/725/builds/12170) and take a look at the build logs.
Check if the failure is related to this commit (574405c) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/725/builds/12170

Failed tests:

test_urllib2net

Failed subtests:

test_ftp_timeout - test.test_urllib2net.TimeoutTest.test_ftp_timeout

Summary of the results of the build (if available):

Click to see traceback logs

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 20, in _retry_thrice
    return func(*args, **kwargs)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 187, in urlopen
    return opener.open(url, data, timeout)
           ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 487, in open
    response = self._open(req, data)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 504, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
                              '_open', req)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 464, in _call_chain
    result = func(*args)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1556, in ftp_open
    raise URLError(f"ftp error: {exp}") from exp
urllib.error.URLError: <urlopen error ftp error: [Errno 60] Operation timed out>


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 22, in _retry_thrice
    last_exc = e
    ^^^^^^^^
ResourceWarning: unclosed <socket.socket fd=7, family=2, type=1, proto=6, laddr=('192.168.0.101', 54826), raddr=('68.183.26.59', 21)>
Warning -- Unraisable exception
Exception ignored while finalizing socket <socket.socket fd=8, family=2, type=1, proto=6, laddr=('192.168.0.101', 54828), raddr=('68.183.26.59', 21)>:
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1546, in ftp_open
    fp, retrlen = fw.retrfile(file, type)
                  ~~~~~~~~~~~^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1826, in retrfile
    conn, retrlen = self.ftp.ntransfercmd(cmd)
                    ~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/ftplib.py", line 354, in ntransfercmd
    conn = socket.create_connection((host, port), self.timeout,
                                    source_address=self.source_address)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/socket.py", line 879, in create_connection
    raise exceptions[0]
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/socket.py", line 864, in create_connection
    sock.connect(sa)
    ~~~~~~~~~~~~^^^^
TimeoutError: [Errno 60] Operation timed out


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
    ~~~~~~~~~~^^
ResourceWarning: unclosed <socket.socket fd=6, family=2, type=1, proto=6, laddr=('192.168.0.101', 54818), raddr=('68.183.26.59', 21)>


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 22, in _retry_thrice
    last_exc = e
    ^^^^^^^^
ResourceWarning: unclosed <socket.socket fd=8, family=2, type=1, proto=6, laddr=('192.168.0.101', 54828), raddr=('68.183.26.59', 21)>
ERROR


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/libregrtest/single.py", line 165, in _load_run_test
    regrtest_runner(result, test_func, runtests)
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/libregrtest/single.py", line 118, in regrtest_runner
    test_result = test_func()
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/libregrtest/single.py", line 162, in test_func
    return run_unittest(test_mod, runtests)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/libregrtest/single.py", line 42, in run_unittest
    return _run_suite(tests)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/libregrtest/single.py", line 105, in _run_suite
    raise support.TestFailedWithDetails(err, errors, failures, stats=stats)


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 22, in _retry_thrice
    last_exc = e
    ^^^^^^^^
ResourceWarning: unclosed <socket.socket fd=6, family=2, type=1, proto=6, laddr=('192.168.0.101', 54274), raddr=('68.183.26.59', 21)>
Warning -- Unraisable exception
Exception ignored while finalizing socket <socket.socket fd=8, family=2, type=1, proto=6, laddr=('192.168.0.101', 54621), raddr=('68.183.26.59', 21)>:
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1546, in ftp_open
    fp, retrlen = fw.retrfile(file, type)
                  ~~~~~~~~~~~^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1826, in retrfile
    conn, retrlen = self.ftp.ntransfercmd(cmd)
                    ~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/ftplib.py", line 354, in ntransfercmd
    conn = socket.create_connection((host, port), self.timeout,
                                    source_address=self.source_address)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/socket.py", line 879, in create_connection
    raise exceptions[0]
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/socket.py", line 864, in create_connection
    sock.connect(sa)
    ~~~~~~~~~~~~^^^^
TimeoutError: [Errno 60] Operation timed out


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 22, in _retry_thrice
    last_exc = e
    ^^^^^^^^
ResourceWarning: unclosed <socket.socket fd=8, family=2, type=1, proto=6, laddr=('192.168.0.101', 54621), raddr=('68.183.26.59', 21)>
ERROR


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
    ~~~~~~~~~~^^
ResourceWarning: unclosed <socket.socket fd=7, family=2, type=1, proto=6, laddr=('192.168.0.101', 54830), raddr=('68.183.26.59', 21)>


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1546, in ftp_open
    fp, retrlen = fw.retrfile(file, type)
                  ~~~~~~~~~~~^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1826, in retrfile
    conn, retrlen = self.ftp.ntransfercmd(cmd)
                    ~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/ftplib.py", line 354, in ntransfercmd
    conn = socket.create_connection((host, port), self.timeout,
                                    source_address=self.source_address)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/socket.py", line 879, in create_connection
    raise exceptions[0]
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/socket.py", line 864, in create_connection
    sock.connect(sa)
    ~~~~~~~~~~~~^^^^
TimeoutError: [Errno 60] Operation timed out


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 351, in test_ftp_timeout
    u = _urlopen_with_retry(self.FTP_HOST, timeout=60)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 28, in wrapped
    return _retry_thrice(func, exc, *args, **kwargs)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 24, in _retry_thrice
    raise last_exc
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_urllib2net.py", line 20, in _retry_thrice
    return func(*args, **kwargs)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 187, in urlopen
    return opener.open(url, data, timeout)
           ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 487, in open
    response = self._open(req, data)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 504, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
                              '_open', req)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 464, in _call_chain
    result = func(*args)
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/urllib/request.py", line 1556, in ftp_open
    raise URLError(f"ftp error: {exp}") from exp
urllib.error.URLError: <urlopen error ftp error: [Errno 60] Operation timed out>

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colesbury added a commit that referenced this pull request

Oct 23, 2025


          [3.14] gh-140431: Fix GC crash due to partially initialized coroutines (

3944e9b

gh-140470) (gh-140504)

The `make_gen()` function creates and tracks generator/coro objects, but
doesn't fully initialize all the fields. At a minimum, we need to
initialize all the fields that may be accessed by gen_traverse because
the call to `compute_cr_origin()` can trigger a GC.
(cherry picked from commit 574405c)

Co-authored-by: Sam Gross <[email protected]>

StanFromIreland pushed a commit to StanFromIreland/cpython that referenced this pull request

Dec 6, 2025


          pythongh-140431: Fix GC crash due to partially initialized coroutines (…

34a94e4

…pythongh-140470)

The `make_gen()` function creates and tracks generator/coro objects, but
doesn't fully initialize all the fields. At a minimum, we need to
initialize all the fields that may be accessed by gen_traverse because
the call to `compute_cr_origin()` can trigger a GC.

Reviewers

efimov-mikhail

efimov-mikhail approved these changes

kumaraditya303

kumaraditya303 approved these changes

markshannon

Awaiting requested review from markshannon

markshannon is a code owner

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colesbury commented Oct 22, 2025 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

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miss-islington-app Bot commented Oct 23, 2025

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bedevere-bot commented Oct 23, 2025

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

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colesbury commented Oct 22, 2025 •

edited by bedevere-app Bot

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pgdr commented Oct 23, 2025 •

edited

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