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GeezerVison is showing github.com — gh-151524: Avoid using instrumentation callback result after Py_DECREF by lpyu001 · Pull Request #151525 · python/cpython

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@lpyu001

@lpyu001 lpyu001 commented Jun 16, 2026 •
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  • Issue: instrumentation.c: Use-after-Py_DECREF comparison in call_one_instrument #151524

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@lpyu001
pythongh-151524: Avoid using instrumentation callback result after Py…
a4cc0af 
…_DECREF
@bedevere-app bedevere-app Bot added the awaiting review label Jun 16, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Jun 16, 2026
instrumentation.c: Use-after-Py_DECREF comparison in call_one_instrument #151524
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@chris-eibl
chris-eibl self-requested a review June 16, 2026 05:28
chris-eibl
chris-eibl requested changes Jun 16, 2026
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The change lgtm, but I'd create a news entry, like almost all of the fixes for the umbrella issue #146102 did so far.

cc @pablogsal

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@bedevere-app bedevere-app Bot added awaiting changes and removed awaiting review labels Jun 16, 2026
@bedevere-app

bedevere-app Bot commented Jun 16, 2026

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A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.
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@lpyu001
add NEWS
137a1bf
@lpyu001

lpyu001 commented Jun 16, 2026

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The change lgtm, but I'd create a news entry, like almost all of the fixes for the umbrella issue #146102 did so far.

cc @pablogsal

I’ve submitted the news entry.thanks
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chris-eibl
chris-eibl approved these changes Jun 16, 2026
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting changes labels Jun 16, 2026
sobolevn
sobolevn reviewed Jun 16, 2026
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Question: was it ever tested? Or was just the RC of res higher than 1, so no crash happened?

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Comment thread Misc/NEWS.d/next/Core_and_Builtins/2026-06-16-13-50-13.gh-issue-151377.mCqrGg.rst Outdated
@@ -0,0 +1,2 @@
Avoid comparing the result of a ``sys.monitoring`` callback after

@sobolevn sobolevn Jun 16, 2026

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This would be a user-facing news entry. Users care about crashes (which could happen here), not about RC :)
Let's rephrase it.

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ZeroIntensity
ZeroIntensity requested changes Jun 16, 2026
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This isn't UB. _PyInstrumentation_DISABLE is an immortal object; Py_DECREF operations on it are a no-op.

>>> import sys
>>> sys._is_immortal(sys.monitoring.DISABLE)
True

That said, I do agree that it's misleading. Let's either remove the Py_DECREF call entirely and/or add an assertion that it's immortal.

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Comment thread Misc/NEWS.d/next/Core_and_Builtins/2026-06-16-13-50-13.gh-issue-151377.mCqrGg.rst Resolved

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@bedevere-app bedevere-app Bot added awaiting changes and removed awaiting merge labels Jun 16, 2026
@bedevere-app

bedevere-app Bot commented Jun 16, 2026

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A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.
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@ZeroIntensity ZeroIntensity added the skip news label Jun 16, 2026
@lpyu001
update
67821dc
@aisk

aisk commented Jul 21, 2026

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Hi @lpyu001 I see you made some update on this PR, and currently I think it look fine. Can you reply "I have made the requested changes; please review again" in the comments as the bot said, to require other reviewers continue the work?
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@lpyu001

lpyu001 commented Jul 22, 2026

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I have made the requested changes; please review again
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@bedevere-app bedevere-app Bot added awaiting change review and removed awaiting changes labels Jul 22, 2026
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bedevere-app Bot commented Jul 22, 2026

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Thanks for making the requested changes!

@chris-eibl, @ZeroIntensity: please review the changes made to this pull request.
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@bedevere-app
bedevere-app Bot requested review from ZeroIntensity and chris-eibl July 22, 2026 01:18
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chris-eibl approved these changes Jul 23, 2026
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Lgtm and helps me who didn't realize _PyInstrumentation_DISABLE is immortal 👍

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting change review labels Jul 23, 2026
ZeroIntensity
ZeroIntensity approved these changes Jul 23, 2026
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@lpyu001

lpyu001 commented Aug 7, 2026

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The PR has been mergeable for two weeks. Could we go ahead and merge it? @ZeroIntensity @chris-eibl
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aisk
aisk approved these changes Aug 7, 2026
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@ZeroIntensity
ZeroIntensity merged commit 52bed26 into python:main Aug 7, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label Aug 7, 2026
@ZeroIntensity ZeroIntensity added needs backport to 3.13 only security fixes needs backport to 3.14 bugs and security fixes needs backport to 3.15 bugs and security fixes labels Aug 7, 2026
@miss-islington-app

miss-islington-app Bot commented Aug 7, 2026

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Thanks @lpyu001 for the PR, and @ZeroIntensity for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖
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@miss-islington-app

miss-islington-app Bot commented Aug 7, 2026

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Thanks @lpyu001 for the PR, and @ZeroIntensity for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖
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@miss-islington-app

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Thanks @lpyu001 for the PR, and @ZeroIntensity for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖
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@bedevere-app

bedevere-app Bot commented Aug 7, 2026

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GH-155349 is a backport of this pull request to the 3.14 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Aug 7, 2026
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bedevere-app Bot commented Aug 7, 2026

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GH-155350 is a backport of this pull request to the 3.15 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label Aug 7, 2026
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GH-155351 is a backport of this pull request to the 3.13 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.13 only security fixes label Aug 7, 2026
ZeroIntensity pushed a commit that referenced this pull request Aug 7, 2026
@miss-islington @lpyu001
[3.13] gh-151524: Make it clearer that _PyInstrumentation_DISABLE i…
2e19855 
…s immortal in the code (GH-151525) (GH-155351)

(cherry picked from commit 52bed26)

Co-authored-by: stevens <[email protected]>
ZeroIntensity pushed a commit that referenced this pull request Aug 7, 2026
@miss-islington @lpyu001
[3.14] gh-151524: Make it clearer that _PyInstrumentation_DISABLE i…
87bacf1 
…s immortal in the code (GH-151525) (GH-155349)

(cherry picked from commit 52bed26)

Co-authored-by: stevens <[email protected]>
@bedevere-bot

bedevere-bot commented Aug 7, 2026

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⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Arch Linux Asan Debug 3.13 (tierless) has failed when building commit 2e19855.

What do you need to do:

  1. Don't panic.
  2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
  3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1439/builds/1152) and take a look at the build logs.
  4. Check if the failure is related to this commit (2e19855) or if it is a false positive.
  5. 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/1439/builds/1152

Failed tests:

  • test_io

Failed subtests:

  • test_daemon_threads_shutdown_stdout_deadlock - test.test_io.CMiscIOTest.test_daemon_threads_shutdown_stdout_deadlock
  • test_daemon_threads_shutdown_stderr_deadlock - test.test_io.CMiscIOTest.test_daemon_threads_shutdown_stderr_deadlock

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

==

Click to see traceback logs 
Traceback (most recent call last):
  File "/buildbot/buildarea/3.13.pablogsal-arch-x86_64.asan_debug/build/Lib/test/test_io.py", line 4755, in test_daemon_threads_shutdown_stderr_deadlock
    self.check_daemon_threads_shutdown_deadlock('stderr')
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/buildbot/buildarea/3.13.pablogsal-arch-x86_64.asan_debug/build/Lib/test/test_io.py", line 4743, in check_daemon_threads_shutdown_deadlock
    self.assertRegex(err, pattern)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
AssertionError: Regex didn't match: "Fatal Python error: _enter_buffered_busy: could not acquire lock for <(_io\\.)?BufferedWriter name='<stderr>'> at interpreter shutdown, possibly due to daemon threads" not found in '...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
...............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................


Traceback (most recent call last):
  File "/buildbot/buildarea/3.13.pablogsal-arch-x86_64.asan_debug/build/Lib/test/test_io.py", line 4755, in test_daemon_threads_shutdown_stderr_deadlock
    self.check_daemon_threads_shutdown_deadlock('stderr')
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/buildbot/buildarea/3.13.pablogsal-arch-x86_64.asan_debug/build/Lib/test/test_io.py", line 4743, in check_daemon_threads_shutdown_deadlock
    self.assertRegex(err, pattern)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
AssertionError: Regex didn't match: "Fatal Python error: _enter_buffered_busy: could not acquire lock for <(_io\\.)?BufferedWriter name='<stderr>'> at interpreter shutdown, possibly due to daemon threads" not found in '....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................


Traceback (most recent call last):
  File "/buildbot/buildarea/3.13.pablogsal-arch-x86_64.asan_debug/build/Lib/test/test_io.py", line 4750, in test_daemon_threads_shutdown_stdout_deadlock
    self.check_daemon_threads_shutdown_deadlock('stdout')
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/buildbot/buildarea/3.13.pablogsal-arch-x86_64.asan_debug/build/Lib/test/test_io.py", line 4743, in check_daemon_threads_shutdown_deadlock
    self.assertRegex(err, pattern)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
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@bedevere-bot

bedevere-bot commented Aug 7, 2026

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⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Arch Linux Usan Function 3.13 (tierless) has failed when building commit 2e19855.

What do you need to do:

  1. Don't panic.
  2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
  3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1601/builds/821) and take a look at the build logs.
  4. Check if the failure is related to this commit (2e19855) or if it is a false positive.
  5. 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/1601/builds/821

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

Click to see traceback logs 
Note: switching to '2e19855a1734a47780b42cfcdc9e3f31976c3e7c'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 2e19855a1734a [3.13] gh-151524: Make it clearer that `_PyInstrumentation_DISABLE` is immortal in the code (GH-151525) (GH-155351)
Switched to and reset branch '3.13'

rror: unable to open output file 'Python/pythonrun.o': 'No space left on device'
1 error generated.
make: *** [Makefile:3042: Python/pythonrun.o] Error 1

find: ‘build’: No such file or directory
find: ‘build’: No such file or directory
find: ‘build’: No such file or directory
find: ‘build’: No such file or directory
make: [Makefile:3132: clean-retain-profile] Error 1 (ignored)
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hugovk pushed a commit that referenced this pull request Aug 8, 2026
@miss-islington @lpyu001
[3.15] gh-151524: Make it clearer that _PyInstrumentation_DISABLE i…
a8a3b24 
…s immortal in the code (GH-151525) (#155350)

gh-151524: Make it clearer that `_PyInstrumentation_DISABLE` is immortal in the code (GH-151525)
(cherry picked from commit 52bed26)

Co-authored-by: stevens <[email protected]>
mbeijen pushed a commit to mbeijen/cpython that referenced this pull request Aug 14, 2026
@lpyu001 @mbeijen
pythongh-151524: Make it clearer that _PyInstrumentation_DISABLE is…
c19e850 
… immortal in the code (pythonGH-151525)
@lpyu001
lpyu001 deleted the fix-use-after-Py_DECREF-comparison2 branch September 23, 2026 02:54
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@sobolevn sobolevn sobolevn left review comments
@aisk aisk aisk approved these changes
@ZeroIntensity ZeroIntensity ZeroIntensity approved these changes
@chris-eibl chris-eibl chris-eibl approved these changes

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@lpyu001 @aisk @bedevere-bot @sobolevn @ZeroIntensity @chris-eibl
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