From 4652f0dbec49d56f17d36365743e0a988a960113 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 06:53:07 -0400
Subject: [PATCH 01/24] Convert the gilstate into a thread-local.

---
 Include/internal/pycore_runtime_init.h    |   3 -
 Include/internal/pycore_runtime_structs.h |   6 -
 Python/pystate.c                          | 182 ++++------------------
 3 files changed, 31 insertions(+), 160 deletions(-)

diff --git a/Include/internal/pycore_runtime_init.h b/Include/internal/pycore_runtime_init.h
index 2b2e439681f459..e40698dba732fd 100644
--- a/Include/internal/pycore_runtime_init.h
+++ b/Include/internal/pycore_runtime_init.h
@@ -61,9 +61,6 @@ extern PyTypeObject _PyExc_MemoryError;
                 }, \
             }, \
         }, \
-        /* A TSS key must be initialized with Py_tss_NEEDS_INIT \
-           in accordance with the specification. */ \
-        .autoTSSkey = Py_tss_NEEDS_INIT, \
         .parser = _parser_runtime_state_INIT, \
         .ceval = { \
             .pending_mainthread = { \
diff --git a/Include/internal/pycore_runtime_structs.h b/Include/internal/pycore_runtime_structs.h
index 6bf3aae7175a97..d5e5531350af74 100644
--- a/Include/internal/pycore_runtime_structs.h
+++ b/Include/internal/pycore_runtime_structs.h
@@ -223,12 +223,6 @@ struct pyruntimestate {
     struct _pythread_runtime_state threads;
     struct _signals_runtime_state signals;
 
-    /* Used for the thread state bound to the current thread. */
-    Py_tss_t autoTSSkey;
-
-    /* Used instead of PyThreadState.trash when there is not current tstate. */
-    Py_tss_t trashTSSkey;
-
     PyWideStringList orig_argv;
 
     struct _parser_runtime_state parser;
diff --git a/Python/pystate.c b/Python/pystate.c
index ee35f0fa945f8b..525e27b4fa0d24 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -69,7 +69,10 @@ to avoid the expense of doing their own locking).
 
 
 #ifdef HAVE_THREAD_LOCAL
+/* The attached thread state for the current thread. */
 _Py_thread_local PyThreadState *_Py_tss_tstate = NULL;
+/* The bound gilstate for the current thread. */
+_Py_thread_local PyThreadState *_Py_tss_gilstate = NULL;
 #endif
 
 static inline PyThreadState *
@@ -118,78 +121,9 @@ _PyThreadState_GetCurrent(void)
 }
 
 
-//------------------------------------------------
-// the thread state bound to the current OS thread
-//------------------------------------------------
-
-static inline int
-tstate_tss_initialized(Py_tss_t *key)
-{
-    return PyThread_tss_is_created(key);
-}
-
-static inline int
-tstate_tss_init(Py_tss_t *key)
-{
-    assert(!tstate_tss_initialized(key));
-    return PyThread_tss_create(key);
-}
-
-static inline void
-tstate_tss_fini(Py_tss_t *key)
-{
-    assert(tstate_tss_initialized(key));
-    PyThread_tss_delete(key);
-}
-
-static inline PyThreadState *
-tstate_tss_get(Py_tss_t *key)
-{
-    assert(tstate_tss_initialized(key));
-    return (PyThreadState *)PyThread_tss_get(key);
-}
-
-static inline int
-tstate_tss_set(Py_tss_t *key, PyThreadState *tstate)
-{
-    assert(tstate != NULL);
-    assert(tstate_tss_initialized(key));
-    return PyThread_tss_set(key, (void *)tstate);
-}
-
-static inline int
-tstate_tss_clear(Py_tss_t *key)
-{
-    assert(tstate_tss_initialized(key));
-    return PyThread_tss_set(key, (void *)NULL);
-}
-
-#ifdef HAVE_FORK
-/* Reset the TSS key - called by PyOS_AfterFork_Child().
- * This should not be necessary, but some - buggy - pthread implementations
- * don't reset TSS upon fork(), see issue #10517.
- */
-static PyStatus
-tstate_tss_reinit(Py_tss_t *key)
-{
-    if (!tstate_tss_initialized(key)) {
-        return _PyStatus_OK();
-    }
-    PyThreadState *tstate = tstate_tss_get(key);
-
-    tstate_tss_fini(key);
-    if (tstate_tss_init(key) != 0) {
-        return _PyStatus_NO_MEMORY();
-    }
-
-    /* If the thread had an associated auto thread state, reassociate it with
-     * the new key. */
-    if (tstate && tstate_tss_set(key, tstate) != 0) {
-        return _PyStatus_ERR("failed to re-set autoTSSkey");
-    }
-    return _PyStatus_OK();
-}
-#endif
+//---------------------------------------------
+// the GIL state bound to the current OS thread
+//---------------------------------------------
 
 
 /*
@@ -198,36 +132,23 @@ tstate_tss_reinit(Py_tss_t *key)
    The GIL does no need to be held for these.
   */
 
-#define gilstate_tss_initialized(runtime) \
-    tstate_tss_initialized(&(runtime)->autoTSSkey)
-#define gilstate_tss_init(runtime) \
-    tstate_tss_init(&(runtime)->autoTSSkey)
-#define gilstate_tss_fini(runtime) \
-    tstate_tss_fini(&(runtime)->autoTSSkey)
-#define gilstate_tss_get(runtime) \
-    tstate_tss_get(&(runtime)->autoTSSkey)
-#define _gilstate_tss_set(runtime, tstate) \
-    tstate_tss_set(&(runtime)->autoTSSkey, tstate)
-#define _gilstate_tss_clear(runtime) \
-    tstate_tss_clear(&(runtime)->autoTSSkey)
-#define gilstate_tss_reinit(runtime) \
-    tstate_tss_reinit(&(runtime)->autoTSSkey)
+static inline PyThreadState *
+gilstate_get(void)
+{
+    return _Py_tss_gilstate;
+}
 
 static inline void
-gilstate_tss_set(_PyRuntimeState *runtime, PyThreadState *tstate)
+gilstate_set(PyThreadState *tstate)
 {
-    assert(tstate != NULL && tstate->interp->runtime == runtime);
-    if (_gilstate_tss_set(runtime, tstate) != 0) {
-        Py_FatalError("failed to set current tstate (TSS)");
-    }
+    assert(tstate != NULL);
+    _Py_tss_gilstate = tstate;
 }
 
 static inline void
-gilstate_tss_clear(_PyRuntimeState *runtime)
+gilstate_clear(void)
 {
-    if (_gilstate_tss_clear(runtime) != 0) {
-        Py_FatalError("failed to clear current tstate (TSS)");
-    }
+    _Py_tss_gilstate = NULL;
 }
 
 
@@ -253,7 +174,7 @@ bind_tstate(PyThreadState *tstate)
     assert(tstate_is_alive(tstate) && !tstate->_status.bound);
     assert(!tstate->_status.unbound);  // just in case
     assert(!tstate->_status.bound_gilstate);
-    assert(tstate != gilstate_tss_get(tstate->interp->runtime));
+    assert(tstate != gilstate_get());
     assert(!tstate->_status.active);
     assert(tstate->thread_id == 0);
     assert(tstate->native_thread_id == 0);
@@ -328,14 +249,13 @@ bind_gilstate_tstate(PyThreadState *tstate)
     // XXX assert(!tstate->_status.active);
     assert(!tstate->_status.bound_gilstate);
 
-    _PyRuntimeState *runtime = tstate->interp->runtime;
-    PyThreadState *tcur = gilstate_tss_get(runtime);
+    PyThreadState *tcur = gilstate_get();
     assert(tstate != tcur);
 
     if (tcur != NULL) {
         tcur->_status.bound_gilstate = 0;
     }
-    gilstate_tss_set(runtime, tstate);
+    gilstate_set(tstate);
     tstate->_status.bound_gilstate = 1;
 }
 
@@ -347,9 +267,9 @@ unbind_gilstate_tstate(PyThreadState *tstate)
     assert(tstate_is_bound(tstate));
     // XXX assert(!tstate->_status.active);
     assert(tstate->_status.bound_gilstate);
-    assert(tstate == gilstate_tss_get(tstate->interp->runtime));
+    assert(tstate == gilstate_get());
 
-    gilstate_tss_clear(tstate->interp->runtime);
+    gilstate_clear();
     tstate->_status.bound_gilstate = 0;
 }
 
@@ -373,7 +293,7 @@ holds_gil(PyThreadState *tstate)
     // (and tstate->interp->runtime->ceval.gil.locked).
     assert(tstate != NULL);
     /* Must be the tstate for this thread */
-    assert(tstate == gilstate_tss_get(tstate->interp->runtime));
+    assert(tstate == gilstate_get());
     return tstate == current_fast_get();
 }
 
@@ -469,16 +389,6 @@ _PyRuntimeState_Init(_PyRuntimeState *runtime)
         return status;
     }
 
-    if (gilstate_tss_init(runtime) != 0) {
-        _PyRuntimeState_Fini(runtime);
-        return _PyStatus_NO_MEMORY();
-    }
-
-    if (PyThread_tss_create(&runtime->trashTSSkey) != 0) {
-        _PyRuntimeState_Fini(runtime);
-        return _PyStatus_NO_MEMORY();
-    }
-
     init_runtime(runtime, open_code_hook, open_code_userdata, audit_hook_head,
                  unicode_next_index);
 
@@ -492,14 +402,6 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
     /* The count is cleared by _Py_FinalizeRefTotal(). */
     assert(runtime->object_state.interpreter_leaks == 0);
 #endif
-
-    if (gilstate_tss_initialized(runtime)) {
-        gilstate_tss_fini(runtime);
-    }
-
-    if (PyThread_tss_is_created(&runtime->trashTSSkey)) {
-        PyThread_tss_delete(&runtime->trashTSSkey);
-    }
 }
 
 #ifdef HAVE_FORK
@@ -532,18 +434,6 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
 
     _PyTypes_AfterFork();
 
-    PyStatus status = gilstate_tss_reinit(runtime);
-    if (_PyStatus_EXCEPTION(status)) {
-        return status;
-    }
-
-    if (PyThread_tss_is_created(&runtime->trashTSSkey)) {
-        PyThread_tss_delete(&runtime->trashTSSkey);
-    }
-    if (PyThread_tss_create(&runtime->trashTSSkey) != 0) {
-        return _PyStatus_NO_MEMORY();
-    }
-
     _PyThread_AfterFork(&runtime->threads);
 
     return _PyStatus_OK();
@@ -1629,7 +1519,7 @@ _PyThreadState_NewBound(PyInterpreterState *interp, int whence)
         bind_tstate(tstate);
         // This makes sure there's a gilstate tstate bound
         // as soon as possible.
-        if (gilstate_tss_get(tstate->interp->runtime) == NULL) {
+        if (gilstate_get() == NULL) {
             bind_gilstate_tstate(tstate);
         }
     }
@@ -2050,7 +1940,7 @@ tstate_activate(PyThreadState *tstate)
     assert(!tstate->_status.active);
 
     assert(!tstate->_status.bound_gilstate ||
-           tstate == gilstate_tss_get((tstate->interp->runtime)));
+           tstate == gilstate_get());
     if (!tstate->_status.bound_gilstate) {
         bind_gilstate_tstate(tstate);
     }
@@ -2515,7 +2405,7 @@ _PyThreadState_Bind(PyThreadState *tstate)
     bind_tstate(tstate);
     // This makes sure there's a gilstate tstate bound
     // as soon as possible.
-    if (gilstate_tss_get(tstate->interp->runtime) == NULL) {
+    if (gilstate_get() == NULL) {
         bind_gilstate_tstate(tstate);
     }
 }
@@ -2717,7 +2607,7 @@ _PyGILState_Init(PyInterpreterState *interp)
         return _PyStatus_OK();
     }
     _PyRuntimeState *runtime = interp->runtime;
-    assert(gilstate_tss_get(runtime) == NULL);
+    assert(gilstate_get() == NULL);
     assert(runtime->gilstate.autoInterpreterState == NULL);
     runtime->gilstate.autoInterpreterState = interp;
     return _PyStatus_OK();
@@ -2753,7 +2643,7 @@ _PyGILState_SetTstate(PyThreadState *tstate)
     _PyRuntimeState *runtime = tstate->interp->runtime;
 
     assert(runtime->gilstate.autoInterpreterState == tstate->interp);
-    assert(gilstate_tss_get(runtime) == tstate);
+    assert(gilstate_get() == tstate);
     assert(tstate->gilstate_counter == 1);
 #endif
 }
@@ -2769,11 +2659,7 @@ _PyGILState_GetInterpreterStateUnsafe(void)
 PyThreadState *
 PyGILState_GetThisThreadState(void)
 {
-    _PyRuntimeState *runtime = &_PyRuntime;
-    if (!gilstate_tss_initialized(runtime)) {
-        return NULL;
-    }
-    return gilstate_tss_get(runtime);
+    return gilstate_get();
 }
 
 int
@@ -2784,16 +2670,12 @@ PyGILState_Check(void)
         return 1;
     }
 
-    if (!gilstate_tss_initialized(runtime)) {
-        return 1;
-    }
-
     PyThreadState *tstate = current_fast_get();
     if (tstate == NULL) {
         return 0;
     }
 
-    PyThreadState *tcur = gilstate_tss_get(runtime);
+    PyThreadState *tcur = gilstate_get();
     return (tstate == tcur);
 }
 
@@ -2810,10 +2692,9 @@ PyGILState_Ensure(void)
     /* Ensure that _PyEval_InitThreads() and _PyGILState_Init() have been
        called by Py_Initialize() */
     assert(_PyEval_ThreadsInitialized());
-    assert(gilstate_tss_initialized(runtime));
     assert(runtime->gilstate.autoInterpreterState != NULL);
 
-    PyThreadState *tcur = gilstate_tss_get(runtime);
+    PyThreadState *tcur = gilstate_get();
     int has_gil;
     if (tcur == NULL) {
         /* Create a new Python thread state for this thread */
@@ -2853,8 +2734,7 @@ PyGILState_Ensure(void)
 void
 PyGILState_Release(PyGILState_STATE oldstate)
 {
-    _PyRuntimeState *runtime = &_PyRuntime;
-    PyThreadState *tstate = gilstate_tss_get(runtime);
+    PyThreadState *tstate = gilstate_get();
     if (tstate == NULL) {
         Py_FatalError("auto-releasing thread-state, "
                       "but no thread-state for this thread");

From 0e93b0351995e9fd63e04d26f722e53252f32715 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 06:54:44 -0400
Subject: [PATCH 02/24] Add a comment.

---
 Python/pystate.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Python/pystate.c b/Python/pystate.c
index 525e27b4fa0d24..0c21a12079cff1 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -71,7 +71,11 @@ to avoid the expense of doing their own locking).
 #ifdef HAVE_THREAD_LOCAL
 /* The attached thread state for the current thread. */
 _Py_thread_local PyThreadState *_Py_tss_tstate = NULL;
-/* The bound gilstate for the current thread. */
+
+/* The bound gilstate for the current thread.
+   Basically, this is used for caching the right interpreter
+   for subsequent PyGILState_Ensure() calls. Despite the name,
+   this doesn't have much to do with the actual GIL. */
 _Py_thread_local PyThreadState *_Py_tss_gilstate = NULL;
 #endif
 

From ba4c00ee48be4ff33e5082e386fbf4e53b60792f Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 06:59:22 -0400
Subject: [PATCH 03/24] Add a test case.

---
 Programs/_testembed.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 6f6d0cae58010e..99cf7919cfa63f 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -1,5 +1,6 @@
 #ifndef Py_BUILD_CORE_MODULE
 #  define Py_BUILD_CORE_MODULE
+#include "pystate.h"
 #endif
 
 /* Always enable assertion (even in release mode) */
@@ -2341,6 +2342,27 @@ test_get_incomplete_frame(void)
     return result;
 }
 
+static void do_gilstate_ensure(void *unused)
+{
+    for (int i = 0; i < 50; ++i) {
+        PyGILState_STATE gstate = PyGILState_Ensure();
+        assert(PyGILState_Check()); // Yuck
+        PyGILState_Release(gstate);
+    }
+}
+
+static int
+test_gilstate_after_finalization(void)
+{
+    PyThread_handle_t handle;
+    PyThread_ident_t ident;
+    _testembed_Py_Initialize();
+    if (PyThread_start_joinable_thread(&do_gilstate_ensure, NULL, &ident, &handle) < 0) {
+        return -1;
+    }
+    Py_Finalize();
+    return PyThread_join_thread(handle);
+}
 
 /* *********************************************************
  * List of test cases and the function that implements it.
@@ -2431,7 +2453,7 @@ static struct TestCase TestCases[] = {
     {"test_frozenmain", test_frozenmain},
 #endif
     {"test_get_incomplete_frame", test_get_incomplete_frame},
-
+    {"test_gilstate_after_finalization", test_gilstate_after_finalization},
     {NULL, NULL}
 };
 

From 2e990928a03107473ddb8224290d7ee647dc868a Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 07:05:55 -0400
Subject: [PATCH 04/24] Fix the test.

---
 Programs/_testembed.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 99cf7919cfa63f..f3bd0489767596 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -1,6 +1,5 @@
 #ifndef Py_BUILD_CORE_MODULE
 #  define Py_BUILD_CORE_MODULE
-#include "pystate.h"
 #endif
 
 /* Always enable assertion (even in release mode) */
@@ -2342,7 +2341,8 @@ test_get_incomplete_frame(void)
     return result;
 }
 
-static void do_gilstate_ensure(void *unused)
+static void
+do_gilstate_ensure(void *unused)
 {
     for (int i = 0; i < 50; ++i) {
         PyGILState_STATE gstate = PyGILState_Ensure();
@@ -2354,9 +2354,9 @@ static void do_gilstate_ensure(void *unused)
 static int
 test_gilstate_after_finalization(void)
 {
+    _testembed_Py_Initialize();
     PyThread_handle_t handle;
     PyThread_ident_t ident;
-    _testembed_Py_Initialize();
     if (PyThread_start_joinable_thread(&do_gilstate_ensure, NULL, &ident, &handle) < 0) {
         return -1;
     }

From 6425c3e31156f333b27b3cff0fcf37710323454f Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 07:27:30 -0400
Subject: [PATCH 05/24] Fix the test case (again).

---
 Programs/_testembed.c | 25 ++++++++++++++++---------
 Python/pystate.c      | 11 ++++++-----
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index f3bd0489767596..c1ac330c51ec32 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -8,6 +8,7 @@
 #include <Python.h>
 #include "pycore_initconfig.h"    // _PyConfig_InitCompatConfig()
 #include "pycore_runtime.h"       // _PyRuntime
+#include "pycore_semaphore.h"     // _PySemaphore
 #include "pycore_pythread.h"      // PyThread_start_joinable_thread()
 #include "pycore_import.h"        // _PyImport_FrozenBootstrap
 #include <inttypes.h>
@@ -2342,26 +2343,32 @@ test_get_incomplete_frame(void)
 }
 
 static void
-do_gilstate_ensure(void *unused)
+do_gilstate_ensure(void *semaphore_ptr)
 {
-    for (int i = 0; i < 50; ++i) {
-        PyGILState_STATE gstate = PyGILState_Ensure();
-        assert(PyGILState_Check()); // Yuck
-        PyGILState_Release(gstate);
-    }
+    _PySemaphore *semaphore = (_PySemaphore *)semaphore_ptr;
+    // Signal to the calling thread that we've started
+    _PySemaphore_Wakeup(semaphore);
+    PyGILState_STATE gstate = PyGILState_Ensure(); // This should hang
+    assert(NULL);
 }
 
 static int
 test_gilstate_after_finalization(void)
 {
     _testembed_Py_Initialize();
+    Py_Finalize();
     PyThread_handle_t handle;
     PyThread_ident_t ident;
-    if (PyThread_start_joinable_thread(&do_gilstate_ensure, NULL, &ident, &handle) < 0) {
+    _PySemaphore semaphore;
+    _PySemaphore_Init(&semaphore);
+    if (PyThread_start_joinable_thread(&do_gilstate_ensure, &semaphore, &ident, &handle) < 0) {
         return -1;
     }
-    Py_Finalize();
-    return PyThread_join_thread(handle);
+    _PySemaphore_Wait(&semaphore, /*timeout_ns=*/-1, /*detach=*/0);
+    // We're now pretty confident that the thread went for
+    // PyGILState_Ensure(), but that means it got hung.
+    _PySemaphore_Destroy(&semaphore);
+    return PyThread_detach_thread(handle);
 }
 
 /* *********************************************************
diff --git a/Python/pystate.c b/Python/pystate.c
index 0c21a12079cff1..d4fa3792dfd6c9 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -271,9 +271,9 @@ unbind_gilstate_tstate(PyThreadState *tstate)
     assert(tstate_is_bound(tstate));
     // XXX assert(!tstate->_status.active);
     assert(tstate->_status.bound_gilstate);
-    assert(tstate == gilstate_get());
-
-    gilstate_clear();
+    if (tstate == gilstate_get()) {
+        gilstate_clear();
+    }
     tstate->_status.bound_gilstate = 0;
 }
 
@@ -2695,8 +2695,9 @@ PyGILState_Ensure(void)
 
     /* Ensure that _PyEval_InitThreads() and _PyGILState_Init() have been
        called by Py_Initialize() */
-    assert(_PyEval_ThreadsInitialized());
-    assert(runtime->gilstate.autoInterpreterState != NULL);
+    if (!_PyEval_ThreadsInitialized() || runtime->gilstate.autoInterpreterState == NULL) {
+        PyThread_hang_thread();
+    }
 
     PyThreadState *tcur = gilstate_get();
     int has_gil;

From 78cd775a30c2ad99e5f5eca8919633475798b3eb Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 07:27:59 -0400
Subject: [PATCH 06/24] Remove unused variable.

---
 Programs/_testembed.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index c1ac330c51ec32..a5e9e3d0e87f99 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -2348,7 +2348,7 @@ do_gilstate_ensure(void *semaphore_ptr)
     _PySemaphore *semaphore = (_PySemaphore *)semaphore_ptr;
     // Signal to the calling thread that we've started
     _PySemaphore_Wakeup(semaphore);
-    PyGILState_STATE gstate = PyGILState_Ensure(); // This should hang
+    PyGILState_Ensure(); // This should hang
     assert(NULL);
 }
 

From c8421fc3725cbabba4b4f674748efe73db067ef6 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 07:41:34 -0400
Subject: [PATCH 07/24] Add blurb.

---
 .../next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst   | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst

diff --git a/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst b/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst
new file mode 100644
index 00000000000000..8a19251f88f5be
--- /dev/null
+++ b/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst
@@ -0,0 +1,2 @@
+:c:func:`PyGILState_Ensure` no longer crashes when calling after interpreter
+finalization.

From 0a875ff65d0ac9446ca050d50fc88612bb866723 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 07:54:37 -0400
Subject: [PATCH 08/24] Make the C analyzer happy.

---
 Tools/c-analyzer/cpython/ignored.tsv | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Tools/c-analyzer/cpython/ignored.tsv b/Tools/c-analyzer/cpython/ignored.tsv
index 14dc5007b65861..11a6214822ac99 100644
--- a/Tools/c-analyzer/cpython/ignored.tsv
+++ b/Tools/c-analyzer/cpython/ignored.tsv
@@ -190,6 +190,7 @@ Python/pyfpe.c	-	PyFPE_counter	-
 
 Python/import.c	-	pkgcontext	-
 Python/pystate.c	-	_Py_tss_tstate	-
+Python/pystate.c	-	_Py_tss_gilstate -
 
 ##-----------------------
 ## should be const

From dd330f8060a2139b08cd765e619bdbda8e5b4b80 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 14 Apr 2025 08:07:08 -0400
Subject: [PATCH 09/24] Fix the C analyzer (round 2).

---
 Tools/c-analyzer/cpython/ignored.tsv | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Tools/c-analyzer/cpython/ignored.tsv b/Tools/c-analyzer/cpython/ignored.tsv
index 11a6214822ac99..4576d4cc9ea5a9 100644
--- a/Tools/c-analyzer/cpython/ignored.tsv
+++ b/Tools/c-analyzer/cpython/ignored.tsv
@@ -190,7 +190,7 @@ Python/pyfpe.c	-	PyFPE_counter	-
 
 Python/import.c	-	pkgcontext	-
 Python/pystate.c	-	_Py_tss_tstate	-
-Python/pystate.c	-	_Py_tss_gilstate -
+Python/pystate.c	-	_Py_tss_gilstate	-
 
 ##-----------------------
 ## should be const

From a3c229266565e238ec25227f135cfeba1dfd6990 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Tue, 15 Apr 2025 16:14:52 -0400
Subject: [PATCH 10/24] Add test to test_embed

---
 Lib/test/test_embed.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index e06e684408ca6b..757be365019749 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -1916,6 +1916,10 @@ def test_get_incomplete_frame(self):
         self.run_embedded_interpreter("test_get_incomplete_frame")
 
 
+    def test_gilstate_after_finalization(self):
+        self.run_embedded_interpreter("test_gilstate_after_finalization")
+
+
 class MiscTests(EmbeddingTestsMixin, unittest.TestCase):
     def test_unicode_id_init(self):
         # bpo-42882: Test that _PyUnicode_FromId() works

From 86be7f316d12e2d7e009c3ea85f2cf156b28f6f7 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Tue, 15 Apr 2025 16:15:44 -0400
Subject: [PATCH 11/24] Update
 Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst

Co-authored-by: Sam Gross <colesbury@gmail.com>
---
 .../next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst b/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst
index 8a19251f88f5be..aa0e8bca93b46f 100644
--- a/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst
+++ b/Misc/NEWS.d/next/C_API/2025-04-14-07-41-28.gh-issue-131185.ZCjMHD.rst
@@ -1,2 +1,2 @@
-:c:func:`PyGILState_Ensure` no longer crashes when calling after interpreter
+:c:func:`PyGILState_Ensure` no longer crashes when called after interpreter
 finalization.

From 453a46850fd9c1c5cfdcd1c8275e1d0ee6c4ad3f Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Tue, 15 Apr 2025 16:18:19 -0400
Subject: [PATCH 12/24] Fix some of the comments.

---
 Python/pystate.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/Python/pystate.c b/Python/pystate.c
index d4fa3792dfd6c9..11213d1f2fcb74 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -72,10 +72,8 @@ to avoid the expense of doing their own locking).
 /* The attached thread state for the current thread. */
 _Py_thread_local PyThreadState *_Py_tss_tstate = NULL;
 
-/* The bound gilstate for the current thread.
-   Basically, this is used for caching the right interpreter
-   for subsequent PyGILState_Ensure() calls. Despite the name,
-   this doesn't have much to do with the actual GIL. */
+/* The "bound" thread state used by PyGILState_Ensure(),
+   also known as a "gilstate." */
 _Py_thread_local PyThreadState *_Py_tss_gilstate = NULL;
 #endif
 
@@ -126,10 +124,9 @@ _PyThreadState_GetCurrent(void)
 
 
 //---------------------------------------------
-// the GIL state bound to the current OS thread
+// The thread state used by PyGILState_Ensure()
 //---------------------------------------------
 
-
 /*
    The stored thread state is set by bind_tstate() (AKA PyThreadState_Bind().
 

From da9b606c671e8c9ba95b672d8135629ef677fcb6 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Tue, 15 Apr 2025 16:22:06 -0400
Subject: [PATCH 13/24] Use PyEvent instead of _PySemaphore

---
 Programs/_testembed.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index a5e9e3d0e87f99..0721db7b41afe3 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -2343,11 +2343,11 @@ test_get_incomplete_frame(void)
 }
 
 static void
-do_gilstate_ensure(void *semaphore_ptr)
+do_gilstate_ensure(void *event_ptr)
 {
-    _PySemaphore *semaphore = (_PySemaphore *)semaphore_ptr;
+    PyEvent *event = (PyEvent *)event_ptr;
     // Signal to the calling thread that we've started
-    _PySemaphore_Wakeup(semaphore);
+    _PyEvent_Notify(event);
     PyGILState_Ensure(); // This should hang
     assert(NULL);
 }
@@ -2359,15 +2359,13 @@ test_gilstate_after_finalization(void)
     Py_Finalize();
     PyThread_handle_t handle;
     PyThread_ident_t ident;
-    _PySemaphore semaphore;
-    _PySemaphore_Init(&semaphore);
-    if (PyThread_start_joinable_thread(&do_gilstate_ensure, &semaphore, &ident, &handle) < 0) {
+    PyEvent event = {};
+    if (PyThread_start_joinable_thread(&do_gilstate_ensure, &event, &ident, &handle) < 0) {
         return -1;
     }
-    _PySemaphore_Wait(&semaphore, /*timeout_ns=*/-1, /*detach=*/0);
+    PyEvent_Wait(&event);
     // We're now pretty confident that the thread went for
     // PyGILState_Ensure(), but that means it got hung.
-    _PySemaphore_Destroy(&semaphore);
     return PyThread_detach_thread(handle);
 }
 

From 2f9e499af4bd2202f495ffd4f0a5433f7d973457 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Fri, 18 Apr 2025 12:18:17 -0400
Subject: [PATCH 14/24] Fix scalar initializer.

---
 Programs/_testembed.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 0721db7b41afe3..cb89486946946a 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -2359,7 +2359,7 @@ test_gilstate_after_finalization(void)
     Py_Finalize();
     PyThread_handle_t handle;
     PyThread_ident_t ident;
-    PyEvent event = {};
+    PyEvent event = {0};
     if (PyThread_start_joinable_thread(&do_gilstate_ensure, &event, &ident, &handle) < 0) {
         return -1;
     }

From 0dba178207f63e92a7566811e3122909bf448f84 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Fri, 18 Apr 2025 12:34:12 -0400
Subject: [PATCH 15/24] Add comment about thread-safety.

---
 Python/pystate.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Python/pystate.c b/Python/pystate.c
index 11213d1f2fcb74..8c8dad01115d0b 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2691,7 +2691,12 @@ PyGILState_Ensure(void)
        called Py_Initialize(). */
 
     /* Ensure that _PyEval_InitThreads() and _PyGILState_Init() have been
-       called by Py_Initialize() */
+       called by Py_Initialize()
+
+       TODO: This isn't thread-safe. There's no protection here against
+       concurrent finalization of the interpreter; it's simply a guard
+       for *after* the interpreter has finalized.
+     */
     if (!_PyEval_ThreadsInitialized() || runtime->gilstate.autoInterpreterState == NULL) {
         PyThread_hang_thread();
     }

From 863d2bc89d454275f167df144275941f3dc102a6 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Sun, 18 May 2025 11:55:32 -0400
Subject: [PATCH 16/24] Fix header.

---
 Programs/_testembed.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index cb89486946946a..ec1be1304a1b98 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -8,7 +8,7 @@
 #include <Python.h>
 #include "pycore_initconfig.h"    // _PyConfig_InitCompatConfig()
 #include "pycore_runtime.h"       // _PyRuntime
-#include "pycore_semaphore.h"     // _PySemaphore
+#include "pycore_lock.h"          // PyEvent
 #include "pycore_pythread.h"      // PyThread_start_joinable_thread()
 #include "pycore_import.h"        // _PyImport_FrozenBootstrap
 #include <inttypes.h>

From cad04048a2f142784eeb1c2510f81524f728f67b Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Sun, 18 May 2025 12:18:05 -0400
Subject: [PATCH 17/24] Fix renaming.

---
 Programs/_testembed.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 44bafe4468ef45..577da65c7cdafa 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -2326,7 +2326,7 @@ do_gilstate_ensure(void *event_ptr)
 static int
 test_gilstate_after_finalization(void)
 {
-    _testembed_Py_Initialize();
+    _testembed_initialize();
     Py_Finalize();
     PyThread_handle_t handle;
     PyThread_ident_t ident;

From 779be6efeaa75533bcfe8ea0c0b47e0247efc5c9 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Sun, 18 May 2025 12:18:35 -0400
Subject: [PATCH 18/24] Restore assertion.

---
 Python/pystate.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/Python/pystate.c b/Python/pystate.c
index ccd0ca2a52d954..dfb1ede5651528 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -268,9 +268,8 @@ unbind_gilstate_tstate(PyThreadState *tstate)
     assert(tstate_is_bound(tstate));
     // XXX assert(!tstate->_status.active);
     assert(tstate->_status.bound_gilstate);
-    if (tstate == gilstate_get()) {
-        gilstate_clear();
-    }
+    assert(tstate == gilstate_get());
+    gilstate_clear();
     tstate->_status.bound_gilstate = 0;
 }
 

From 86144fcc78cd7644c3ed6c1654c66048d1128d70 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 19 May 2025 12:24:34 -0400
Subject: [PATCH 19/24] Clear the thread-local.

---
 Python/pystate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Python/pystate.c b/Python/pystate.c
index dfb1ede5651528..2f40380e4b016f 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -402,6 +402,7 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
     /* The count is cleared by _Py_FinalizeRefTotal(). */
     assert(runtime->object_state.interpreter_leaks == 0);
 #endif
+    gilstate_clear();
 }
 
 #ifdef HAVE_FORK
@@ -433,6 +434,7 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
 #endif
 
     _PyTypes_AfterFork();
+    gilstate_clear();
 
     _PyThread_AfterFork(&runtime->threads);
 

From 9f1d919b219048f7eb2caa74e690308f0a9bafb4 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 19 May 2025 12:28:47 -0400
Subject: [PATCH 20/24] Restore trashTSSkey silliness.

---
 Include/internal/pycore_runtime_init.h    | 3 +++
 Include/internal/pycore_runtime_structs.h | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/Include/internal/pycore_runtime_init.h b/Include/internal/pycore_runtime_init.h
index 0837fcb54a3906..4200d91a2fcd9d 100644
--- a/Include/internal/pycore_runtime_init.h
+++ b/Include/internal/pycore_runtime_init.h
@@ -61,6 +61,9 @@ extern PyTypeObject _PyExc_MemoryError;
                 }, \
             }, \
         }, \
+        /* A TSS key must be initialized with Py_tss_NEEDS_INIT \
+           in accordance with the specification. */ \
+        .autoTSSkey = Py_tss_NEEDS_INIT, \
         .parser = _parser_runtime_state_INIT, \
         .ceval = { \
             .pending_mainthread = { \
diff --git a/Include/internal/pycore_runtime_structs.h b/Include/internal/pycore_runtime_structs.h
index d5e5531350af74..12164c7fdd9425 100644
--- a/Include/internal/pycore_runtime_structs.h
+++ b/Include/internal/pycore_runtime_structs.h
@@ -223,6 +223,9 @@ struct pyruntimestate {
     struct _pythread_runtime_state threads;
     struct _signals_runtime_state signals;
 
+    /* Used instead of PyThreadState.trash when there is not current tstate. */
+    Py_tss_t trashTSSkey;
+
     PyWideStringList orig_argv;
 
     struct _parser_runtime_state parser;

From 0c16fea663a0cd5e41de489effd9d00c7cfc6b03 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 19 May 2025 12:37:01 -0400
Subject: [PATCH 21/24] Fix broken build.

---
 Include/internal/pycore_runtime_init.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/Include/internal/pycore_runtime_init.h b/Include/internal/pycore_runtime_init.h
index 4200d91a2fcd9d..b182f7825a2326 100644
--- a/Include/internal/pycore_runtime_init.h
+++ b/Include/internal/pycore_runtime_init.h
@@ -61,9 +61,6 @@ extern PyTypeObject _PyExc_MemoryError;
                 }, \
             }, \
         }, \
-        /* A TSS key must be initialized with Py_tss_NEEDS_INIT \
-           in accordance with the specification. */ \
-        .autoTSSkey = Py_tss_NEEDS_INIT, \
         .parser = _parser_runtime_state_INIT, \
         .ceval = { \
             .pending_mainthread = { \
@@ -236,4 +233,4 @@ extern PyTypeObject _PyExc_MemoryError;
 #ifdef __cplusplus
 }
 #endif
-#endif /* !Py_INTERNAL_RUNTIME_INIT_H */
+#endif /* !Py_INTERNAL_RUNTIME_INIT_H */
\ No newline at end of file

From 7c27c9fb416c7ab1b9b070df08982c630e07ce98 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 19 May 2025 16:56:33 -0400
Subject: [PATCH 22/24] Revert "Clear the thread-local."

This reverts commit 86144fcc78cd7644c3ed6c1654c66048d1128d70.
---
 Python/pystate.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/Python/pystate.c b/Python/pystate.c
index 2f40380e4b016f..dfb1ede5651528 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -402,7 +402,6 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
     /* The count is cleared by _Py_FinalizeRefTotal(). */
     assert(runtime->object_state.interpreter_leaks == 0);
 #endif
-    gilstate_clear();
 }
 
 #ifdef HAVE_FORK
@@ -434,7 +433,6 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
 #endif
 
     _PyTypes_AfterFork();
-    gilstate_clear();
 
     _PyThread_AfterFork(&runtime->threads);
 

From 8f18e95586c03f9e24f85cb1e18bef01af0f1289 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 19 May 2025 16:57:13 -0400
Subject: [PATCH 23/24] Reapply "Clear the thread-local."

This reverts commit 7c27c9fb416c7ab1b9b070df08982c630e07ce98.
---
 Python/pystate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Python/pystate.c b/Python/pystate.c
index dfb1ede5651528..2f40380e4b016f 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -402,6 +402,7 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
     /* The count is cleared by _Py_FinalizeRefTotal(). */
     assert(runtime->object_state.interpreter_leaks == 0);
 #endif
+    gilstate_clear();
 }
 
 #ifdef HAVE_FORK
@@ -433,6 +434,7 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
 #endif
 
     _PyTypes_AfterFork();
+    gilstate_clear();
 
     _PyThread_AfterFork(&runtime->threads);
 

From f90bb119b1b5e6318a938fd5ebf5a90f238a6ed5 Mon Sep 17 00:00:00 2001
From: Peter Bierma <zintensitydev@gmail.com>
Date: Mon, 19 May 2025 23:44:26 -0400
Subject: [PATCH 24/24] Only remove the evil gilstate clear.

---
 Python/pystate.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Python/pystate.c b/Python/pystate.c
index 2f40380e4b016f..3657d958ce12d6 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -434,7 +434,6 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
 #endif
 
     _PyTypes_AfterFork();
-    gilstate_clear();
 
     _PyThread_AfterFork(&runtime->threads);