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ad gh-117657: use relaxed loads for checking dict keys immortality by DinoV · Pull Request #118067 · python/cpython · GitHub
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gh-117657: use relaxed loads for checking dict keys immortality - #118067

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DinoV merged 1 commit into
python:mainfrom
DinoV:nogil_dict_keys_ref_tsan
Apr 19, 2024
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gh-117657: use relaxed loads for checking dict keys immortality#118067
DinoV merged 1 commit into
python:mainfrom
DinoV:nogil_dict_keys_ref_tsan

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@DinoV

@DinoV DinoV commented Apr 18, 2024 •
edited by bedevere-app Bot
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Checking for immortality of dict keys is reported as a TSAN violation, we just need relaxed loads

@DinoV
DinoV requested review from colesbury and mpage April 18, 2024 22:06
@DinoV DinoV changed the title bpo-117657: use relaxed loads for checking dict keys immortality gh-117657: use relaxed loads for checking dict keys immortality Apr 18, 2024
@bedevere-app bedevere-app Bot mentioned this pull request Apr 18, 2024
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colesbury
colesbury approved these changes Apr 18, 2024
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LGTM

Comment thread Objects/dictobject.c
dictkeys_incref(PyDictKeysObject *dk)
{
if (dk->dk_refcnt == _Py_IMMORTAL_REFCNT) {
if (FT_ATOMIC_LOAD_SSIZE_RELAXED(dk->dk_refcnt) == _Py_IMMORTAL_REFCNT) {

@colesbury colesbury Apr 18, 2024

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We could also do dk == Py_EMPTY_KEYS and avoid the atomics, but this seems fine too.

@DinoV DinoV Apr 19, 2024

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I kind of like that, but am a little worried that it'll be overlooked if any other keys become immortal, so I'll just keep it as-is for now.

@DinoV
DinoV marked this pull request as ready for review April 19, 2024 16:24
@DinoV
DinoV merged commit 1e4a4c4 into python:main Apr 19, 2024
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bedevere-bot commented Apr 19, 2024

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⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 RHEL7 LTO 3.x has failed when building commit 1e4a4c4.

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/all/#builders/507/builds/7247) and take a look at the build logs.
  4. Check if the failure is related to this commit (1e4a4c4) 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/all/#builders/507/builds/7247

Failed tests:

  • test_capi

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

==

Click to see traceback logs 
remote: Enumerating objects: 7, done.        
remote: Counting objects:  16% (1/6)        
remote: Counting objects:  33% (2/6)        
remote: Counting objects:  50% (3/6)        
remote: Counting objects:  66% (4/6)        
remote: Counting objects:  83% (5/6)        
remote: Counting objects: 100% (6/6)        
remote: Counting objects: 100% (6/6), done.        
remote: Compressing objects:  16% (1/6)        
remote: Compressing objects:  33% (2/6)        
remote: Compressing objects:  50% (3/6)        
remote: Compressing objects:  66% (4/6)        
remote: Compressing objects:  83% (5/6)        
remote: Compressing objects: 100% (6/6)        
remote: Compressing objects: 100% (6/6), done.        
remote: Total 7 (delta 0), reused 2 (delta 0), pack-reused 1        
From https://github.com/python/cpython
 * branch            main       -> FETCH_HEAD
Note: checking out '1e4a4c4897d0f45b1f594bc429284c82efe49188'.

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 performing another checkout.

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

  git checkout -b new_branch_name

HEAD is now at 1e4a4c4... gh-117657: use relaxed loads for checking dict keys immortality (#118067)
Switched to and reset branch 'main'

make: *** [Makefile:2229: buildbottest] Error 2

@DinoV
DinoV deleted the nogil_dict_keys_ref_tsan branch May 31, 2024 18:22
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Reviewers

@colesbury colesbury colesbury approved these changes
@mpage mpage Awaiting requested review from mpage
@methane methane Awaiting requested review from methane methane is a code owner
@markshannon markshannon Awaiting requested review from markshannon markshannon is a code owner

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