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…dule executes Since pythongh-83065, the first import of pkg.mod kept pkg's module lock until pkg/mod.py had finished executing. Threads needing only the finished pkg were blocked for that long, and concurrent first imports could raise _DeadlockError or a spurious "partially initialized module" ImportError, or hang, with no import cycle involved. Parent packages are now imported, or waited for, before the submodule's lock is taken, and only that lock is held while it executes. The original pythongh-83065 deadlock stays fixed. importlib.import_module() now returns the partially initialized module in a cross-thread circular import, as the import statement already did, instead of raising _DeadlockError.
Documentation build overview
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Address review: shorten the NEWS entry per the updated devguide guidance, reword the What's New entry, and trim the _resolve_parents() docstring and the parent fallback comment in _find_and_load_unlocked().
gpshead
commented
Oct 21, 2026
gpshead
commented
Oct 21, 2026
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Since gh-83065, the first import of pkg.mod kept pkg's module lock until pkg/mod.py had finished executing. This shipped in 3.15.0. Threads needing only the finished pkg were blocked for that long, and concurrent first imports could raise _DeadlockError or a spurious "partially initialized module" ImportError, or hang, with no import cycle involved.
Parent packages are now imported, or waited for, before the submodule's lock is taken, and only that lock is held while it executes. The original gh-83065 deadlock stays fixed.
importlib.import_module() now returns the partially initialized module in a cross-thread circular import, as the import statement already did, instead of raising _DeadlockError.
leaving draft for now while further tests are run - and i want to do a pass over the docs and comments text and such before others take a deep look without knowing that.
authored using Claude.