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gh-151644: Fix data race in sys.setdlopenflags/getdlopenflags under free-threading - #151768
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…nder free-threading In free-threading builds, concurrent calls to sys.getdlopenflags() and sys.setdlopenflags() race on interp->imports.dlopenflags. Fix by using FT_ATOMIC_LOAD_INT_RELAXED / FT_ATOMIC_STORE_INT_RELAXED in _PyImport_GetDLOpenFlags and _PyImport_SetDLOpenFlags, consistent with how analogous interpreter-state integer fields (lazy_imports_mode, pystats_enabled) are protected. Relaxed ordering is correct here: dlopenflags is a standalone config integer with no ordering relationship to other memory. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
zangjiucheng
requested review from
FFY00, brettcannon, ericsnowcurrently, kumaraditya303, ncoghlan and warsaw
as code ownersJune 20, 2026 06:13
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Thanks @zangjiucheng for the PR, and @nascheme for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14. |
Thanks @zangjiucheng for the PR, and @nascheme for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15. |
GH-153789 is a backport of this pull request to the 3.14 branch. |
GH-153790 is a backport of this pull request to the 3.15 branch. |
kumaraditya303 pushed a commit
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Jul 16, 2026
…under free-threading (gh-151768) (#153790) gh-151644: Fix data race in sys.setdlopenflags/getdlopenflags under free-threading (gh-151768) In free-threading builds, concurrent calls to sys.getdlopenflags() and sys.setdlopenflags() race on interp->imports.dlopenflags. Fix by using FT_ATOMIC_LOAD_INT_RELAXED / FT_ATOMIC_STORE_INT_RELAXED in _PyImport_GetDLOpenFlags and _PyImport_SetDLOpenFlags, consistent with how analogous interpreter-state integer fields (lazy_imports_mode, pystats_enabled) are protected. Relaxed ordering is correct here: dlopenflags is a standalone config integer with no ordering relationship to other memory. (cherry picked from commit cde31ec) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com> Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
nascheme pushed a commit
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Jul 17, 2026
…under free-threading (gh-151768) (gh-153789) In free-threading builds, concurrent calls to sys.getdlopenflags() and sys.setdlopenflags() race on interp->imports.dlopenflags. Fix by using FT_ATOMIC_LOAD_INT_RELAXED / FT_ATOMIC_STORE_INT_RELAXED in _PyImport_GetDLOpenFlags and _PyImport_SetDLOpenFlags, consistent with how analogous interpreter-state integer fields (lazy_imports_mode, pystats_enabled) are protected. Relaxed ordering is correct here: dlopenflags is a standalone config integer with no ordering relationship to other memory. (cherry picked from commit cde31ec) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com> Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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In free-threading builds, concurrent calls to
sys.getdlopenflags()andsys.setdlopenflags()race oninterp->imports.dlopenflags— a plainintfield read and written with no synchronisation.
Fix
Replace the bare load/store in
_PyImport_GetDLOpenFlags/_PyImport_SetDLOpenFlagswithFT_ATOMIC_LOAD_INT_RELAXED/FT_ATOMIC_STORE_INT_RELAXED.Atomics are preferred over
PyMutex(used for the analogoubecause each access is a single load or store — no multi-field consistency
guarantee is needed. Relaxed ordering is correct:
dlopenfl standalone config integer with no ordering relationship to other memory, consistent with howlazy_imports_modeandpystats_enablein the same file.
_PyImport_SetDLOpenFlagswhensys.setdlopenflags()is called concurrently #151644