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GeezerVison is showing github.com — gh-117657: Quiet TSAN warnings about remaining non-atomic accesses of `tstate->state` by mpage · Pull Request #118165 · python/cpython

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@mpage

@mpage mpage commented Apr 22, 2024 •
edited by bedevere-app Bot
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These should be the last instances of TSAN warning of data races when accessing tstate->state non-atomically.

TSAN reports a race (example) between accessing tstate->state in _PyThreadState_Suspend():

cpython/Python/pystate.c

Line 2099 in fc21c7f

assert(tstate->state == _Py_THREAD_ATTACHED);

and the compare/exchange in park_detached_threads():

cpython/Python/pystate.c

Lines 2172 to 2173 in fc21c7f

if (_Py_atomic_compare_exchange_int(&t->state,
&state, _Py_THREAD_SUSPENDED)) {

This is a false positive due to TSAN modeling failed compare/exchange operations as writes.

TSAN also reports a race (example) between accessing tstate->state in _PySemaphore_Wait():

cpython/Python/parking_lot.c

Line 197 in fc21c7f

if (tstate && tstate->state == _Py_THREAD_ATTACHED) {

and the compare/exchange in park_detached_threads() above. This is the same issue that we saw in gh-117830.

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

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@mpage
Quiet TSAN warnings about remaining non-atomic accesses of `tstate->s…
c309c66 
…tate`

These should be the last instances of TSAN warning of data races when accessing
`tstate->state` non-atomically.

TSAN reports a race between accessing `tstate->state` in `_PyThreadState_Suspend()`
and the compare/exhange in `park_detached_threads`. This is a false positive due
to TSAN modeling failed compare/exchange operations as writes.

TSAN reports a race between accessing `tstate->state` in `_PySemaphore_Wait()`
and the compare/exchange in `park_detached_threads`. This is the same issue that
we saw in pythongh-117830.
@mpage mpage added the skip news label Apr 23, 2024
@mpage mpage changed the title Quiet TSAN warnings about remaining non-atomic accesses of tstate->state gh-117657: Quiet TSAN warnings about remaining non-atomic accesses of tstate->state Apr 23, 2024
@bedevere-app bedevere-app Bot mentioned this pull request Apr 23, 2024
Make TSAN tests pass with the GIL disabled in free-threaded builds #117657
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@mpage
mpage requested review from DinoV and colesbury April 23, 2024 17:02
@mpage
mpage marked this pull request as ready for review April 23, 2024 17:02
@mpage
mpage requested a review from ericsnowcurrently as a code owner April 23, 2024 17:02
@bedevere-app bedevere-app Bot added the awaiting review label Apr 23, 2024
DinoV
DinoV approved these changes Apr 23, 2024
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LGTM!

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Apr 23, 2024
@DinoV
DinoV merged commit 2e7771a into python:main Apr 23, 2024
@bedevere-app bedevere-app Bot removed the awaiting merge label Apr 23, 2024
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@DinoV DinoV DinoV approved these changes
@colesbury colesbury Awaiting requested review from colesbury
@ericsnowcurrently ericsnowcurrently Awaiting requested review from ericsnowcurrently ericsnowcurrently is a code owner

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2 participants

@mpage @DinoV
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