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GeezerVison is showing github.com — gh-117657: Quiet TSAN warning about a data race between `start_the_world()` and `tstate_try_attach()` by mpage · Pull Request #117828 · python/cpython

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@mpage

@mpage mpage commented Apr 12, 2024 •
edited by bedevere-app Bot
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TSAN erroneously reports a data race (example) between the _Py_atomic_compare_exchange_int on tstate->state in tstate_try_attach():

cpython/Python/pystate.c

Lines 1993 to 1995 in 069de14

return _Py_atomic_compare_exchange_int(&tstate->state,
&expected,
_Py_THREAD_ATTACHED);

and the non-atomic load of tstate->state in start_the_world():

cpython/Python/pystate.c

Line 2251 in 069de14

assert(t->state == _Py_THREAD_SUSPENDED);

The _Py_atomic_compare_exchange_int fails, but TSAN erroneously treats it as a store.

  • Issue: Make TSAN tests pass with the GIL disabled in free-threaded builds #117657

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@mpage
Quiet TSAN warning about a data race between start_the_world() and …
eb46a18 
…`tstate_try_attach()`

TSAN erroneously reports a data race between the `_Py_atomic_compare_exchange_int`
on `tstate->state` in `tstate_try_attach()` and the non-atomic load of
`tstate->state` in `start_the_world`. The `_Py_atomic_compare_exchange_int` fails,
but TSAN erroneously treats it as a store.
@bedevere-app bedevere-app Bot mentioned this pull request Apr 12, 2024
Make TSAN tests pass with the GIL disabled in free-threaded builds #117657
Closed
@mpage mpage added the skip news label Apr 12, 2024
colesbury
colesbury reviewed Apr 12, 2024
View reviewed changes
Comment thread Python/pystate.c Resolved

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@mpage
Use a relaxed load
61bd2fa
@mpage
mpage marked this pull request as ready for review April 12, 2024 22:22
@mpage
mpage requested a review from ericsnowcurrently as a code owner April 12, 2024 22:22
@bedevere-app bedevere-app Bot added the awaiting review label Apr 12, 2024
@mpage
mpage requested a review from colesbury April 12, 2024 22:23
@mpage mpage mentioned this pull request Apr 13, 2024
gh-117657: Quiet more TSAN warnings due to incorrect modeling of compare/exchange #117830
Merged
colesbury
colesbury approved these changes Apr 15, 2024
View reviewed changes
@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Apr 15, 2024
@colesbury
colesbury merged commit 6e0b327 into python:main Apr 15, 2024
@bedevere-app bedevere-app Bot removed the awaiting merge label Apr 15, 2024
mpage added a commit to mpage/cpython that referenced this pull request Apr 16, 2024
@mpage
Remove unneeded free-threading suppressions
da4df93 
The underlying races were fixed in pythongh-117830 and pythongh-117828
diegorusso pushed a commit to diegorusso/cpython that referenced this pull request Apr 17, 2024
@mpage @diegorusso
pythongh-117657: Quiet TSAN warning about a data race between `start_…
2b5a7e4 
…the_world()` and `tstate_try_attach()` (python#117828)

TSAN erroneously reports a data race between the `_Py_atomic_compare_exchange_int`
on `tstate->state` in `tstate_try_attach()` and the non-atomic load of
`tstate->state` in `start_the_world`. The `_Py_atomic_compare_exchange_int` fails,
but TSAN erroneously treats it as a store.
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@colesbury colesbury colesbury approved these changes
@ericsnowcurrently ericsnowcurrently Awaiting requested review from ericsnowcurrently ericsnowcurrently is a code owner

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2 participants

@mpage @colesbury
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