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GeezerVison is showing github.com — gh-127945: fix thread safety of creating instances of ctypes structures by kumaraditya303 · Pull Request #131716 · python/cpython

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@kumaraditya303

@kumaraditya303 kumaraditya303 commented Mar 25, 2025 •
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  • Issue: ctypes thread safety auditing (and fixing) #127945

In free-threading, concurrent mutations to StgInfo is not thread safe. Therefore to make it thread safe, when modifying StgInfo, this PR adds STGINFO_LOCK and STGINFO_UNLOCK macros which are used to acquire critical section of the StgInfo. The critical section is write only and is acquired when modifying the StgInfo fields and while setting the dict_final bit. Once the dict_final is set, StgInfo is treated as read only and no further modifications are allowed. This allows to avoid acquiring the critical section for most read operations when dict_final is set (general case).

Fixes #128567
Fixes #128570

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kumaraditya303 added 9 commits March 25, 2025 10:15
@kumaraditya303
make instance creation thread safe
504e741
@kumaraditya303
add tests
a05195e
@kumaraditya303
Merge branch 'main' of https://github.com/python/cpython into critica…
d515a09 
…l-ctypes
@kumaraditya303
fmt
f3ef75e
@kumaraditya303
wip
e3bec70
@kumaraditya303
fix clearing of final bit
fd5ad20
@kumaraditya303
move setting bit to earlier
ee47298
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add comment
4db3e36
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improve comments
b0e06a0
@kumaraditya303 kumaraditya303 added skip news topic-ctypes topic-free-threading labels Mar 25, 2025
@bedevere-app bedevere-app Bot added the awaiting core review label Mar 25, 2025
@bedevere-app bedevere-app Bot mentioned this pull request Mar 25, 2025
ctypes thread safety auditing (and fixing) #127945
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@kumaraditya303
kumaraditya303 requested a review from colesbury March 25, 2025 13:36
@kumaraditya303 kumaraditya303 added the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Mar 25, 2025
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🤖 New build scheduled with the buildbot fleet by @kumaraditya303 for commit b0e06a0 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F131716%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.
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@bedevere-bot bedevere-bot removed the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Mar 25, 2025
colesbury
colesbury approved these changes Mar 27, 2025
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Looks great! A few minor comments.

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Comment thread Modules/_ctypes/stgdict.c Resolved

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Comment thread Modules/_ctypes/ctypes.h Resolved

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Comment thread Modules/_ctypes/ctypes.h Resolved

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Comment thread Lib/test/test_ctypes/test_free_threading.py Resolved

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Comment thread Modules/_ctypes/_ctypes.c Resolved

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting core review labels Mar 27, 2025
@colesbury
colesbury requested a review from encukou March 27, 2025 23:27
kumaraditya303 added 2 commits March 28, 2025 20:06
@kumaraditya303
Merge branch 'main' of https://github.com/python/cpython into critica…
bfd7c21 
…l-ctypes
@kumaraditya303
code review
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encukou
encukou reviewed Mar 30, 2025
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Comment thread Modules/_ctypes/ctypes.h Resolved

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@kumaraditya303
use uint8_t
2a05687
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kumaraditya303 merged commit bc5a028 into python:main Mar 30, 2025
@bedevere-app bedevere-app Bot removed the awaiting merge label Mar 30, 2025
@kumaraditya303
kumaraditya303 deleted the critical-ctypes branch March 30, 2025 09:52
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@encukou encukou encukou left review comments
@colesbury colesbury colesbury approved these changes

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Successfully merging this pull request may close these issues.

Race in stgdict PyCStructUnionType_update_stginfo under free-threading Race in ctypes PyCFuncPtr_new under free-threading

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@kumaraditya303 @bedevere-bot @encukou @colesbury
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