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gh-146302: make Py_IsInitialized() thread-safe and reflect true init completion #146303

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Merged
gpshead merged 10 commits into from
Apr 11, 2026
Merged

gh-146302: make Py_IsInitialized() thread-safe and reflect true init completion #146303

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1eda370
gh-146302: make Py_IsInitialized() thread-safe and reflect true init …
gpshead Mar 22, 2026
efeae3b
Improve comment wording in pycore_runtime.h accessors
gpshead Mar 22, 2026
3e1eedd
PySys_AddAuditHook: check initialized, not core_initialized
gpshead Mar 22, 2026
59f51a2
Add regression test: Py_IsInitialized() must be false during site import
gpshead Mar 22, 2026
2e3aa7e
Remove unnecessary putenv("PYTHONMALLOC=") from test
gpshead Mar 22, 2026
ba28b37
Address review: use wrapper functions instead of low-level accessors
gpshead Mar 22, 2026
abae231
alphabetical includes, ack that other APIs are used in the comment
gpshead Mar 22, 2026
01df0a2
Address review: use seq-cst atomics for initialized flags
gpshead Mar 23, 2026
ee2d0be
_testembed.test_init_main assert not init per review
gpshead Apr 11, 2026
aec5131
Merge branch 'main' into gh-146302-py-isinitialized-thread-safe
gpshead Apr 11, 2026
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Address review: use seq-cst atomics for initialized flags 
Not performance critical, so use the default ordering rather than
acquire/release.
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@gpshead
gpshead committed Mar 23, 2026
commit 01df0a2eced120b701a228e36ff3dbf611d45de6
12 changes: 6 additions & 6 deletions Include/internal/pycore_runtime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,27 +56,27 @@ _PyRuntimeState_SetFinalizing(_PyRuntimeState *runtime, PyThreadState *tstate) {
}
}

// Release on store, acquire on load: a thread that reads initialized=1
// is guaranteed to observe all writes from the initialization sequence.
// Atomic so a thread that reads initialized=1 observes all writes
// from the initialization sequence (gh-146302).

static inline int
_PyRuntimeState_GetCoreInitialized(_PyRuntimeState *runtime) {
return _Py_atomic_load_int_acquire(&runtime->core_initialized);
return _Py_atomic_load_int(&runtime->core_initialized);
}

static inline void
_PyRuntimeState_SetCoreInitialized(_PyRuntimeState *runtime, int initialized) {
_Py_atomic_store_int_release(&runtime->core_initialized, initialized);
_Py_atomic_store_int(&runtime->core_initialized, initialized);
}

static inline int
_PyRuntimeState_GetInitialized(_PyRuntimeState *runtime) {
return _Py_atomic_load_int_acquire(&runtime->initialized);
return _Py_atomic_load_int(&runtime->initialized);
}

static inline void
_PyRuntimeState_SetInitialized(_PyRuntimeState *runtime, int initialized) {
_Py_atomic_store_int_release(&runtime->initialized, initialized);
_Py_atomic_store_int(&runtime->initialized, initialized);
}


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2 changes: 1 addition & 1 deletion Misc/NEWS.d/next/C_API/2026-03-22-00-00-00.gh-issue-146302.PyIsInit.rst
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@@ -1,3 +1,3 @@
:c:func:`Py_IsInitialized` no longer returns true until initialization has
fully completed, including import of the :mod:`site` module. The underlying
runtime flags now use atomic operations with acquire/release memory ordering.
runtime flags now use atomic operations.
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