Use PyInterpreterConfig.own_gil.

Include/internal/pycore_ceval.h

@@ -97,7 +97,7 @@ _PyEval_Vector(PyThreadState *tstate,
             PyObject *kwnames);
 
 extern int _PyEval_ThreadsInitialized(void);
-extern PyStatus _PyEval_InitGIL(PyThreadState *tstate);
+extern PyStatus _PyEval_InitGIL(PyThreadState *tstate, int own_gil);
 extern void _PyEval_FiniGIL(PyInterpreterState *interp);
 
 extern void _PyEval_ReleaseLock(PyThreadState *tstate);

Include/internal/pycore_ceval_state.h

@@ -86,6 +86,7 @@ struct _pending_calls {
 struct _ceval_state {
     int recursion_limit;
     struct _gil_runtime_state *gil;
+    int own_gil;
     /* This single variable consolidates all requests to break out of
        the fast path in the eval loop. */
     _Py_atomic_int eval_breaker;

Lib/test/test_capi/test_misc.py

@@ -1420,14 +1420,18 @@ def test_configured_settings(self):
 
         # expected to work
         for config, expected in {
-            (True, True, True, True, True, True, True): ALL_FLAGS,
-            (True, False, False, False, False, False, False): OBMALLOC,
+            (True, True, True, True, True, True, True):
+                (ALL_FLAGS, True),
+            (True, False, False, False, False, False, False):
+                (OBMALLOC, False),
             (False, False, False, True, False, True, False):
-                THREADS | EXTENSIONS,
+                (THREADS | EXTENSIONS, False),
         }.items():
             kwargs = dict(zip(kwlist, config))
+            exp_flags, exp_gil = expected
             expected = {
-                'feature_flags': expected,
+                'feature_flags': exp_flags,
+                'own_gil': exp_gil,
             }
             with self.subTest(config):
                 r, w = os.pipe()
@@ -1494,6 +1498,7 @@ def check(enabled, override):
             flags = BASE_FLAGS | EXTENSIONS if enabled else BASE_FLAGS
             settings = {
                 'feature_flags': flags,
+                'own_gil': False,
             }
 
             expected = {

Lib/test/test_embed.py

@@ -1666,6 +1666,7 @@ def test_init_main_interpreter_settings(self):
             # All optional features should be enabled.
             'feature_flags':
                 OBMALLOC | FORK | EXEC | THREADS | DAEMON_THREADS,
+            'own_gil': True,
         }
         out, err = self.run_embedded_interpreter(
             'test_init_main_interpreter_settings',

Lib/test/test_import/__init__.py

@@ -1640,7 +1640,7 @@ class SubinterpImportTests(unittest.TestCase):
     )
     ISOLATED = dict(
         use_main_obmalloc=False,
-        own_gil=False,
+        own_gil=True,
     )
     NOT_ISOLATED = {k: not v for k, v in ISOLATED.items()}
 

Modules/_testinternalcapi.c

@@ -729,6 +729,13 @@ get_interp_settings(PyObject *self, PyObject *args)
         return NULL;
     }
 
+    /* "own GIL" */
+    PyObject *own_gil = interp->ceval.own_gil ? Py_True : Py_False;
+    if (PyDict_SetItemString(settings, "own_gil", own_gil) != 0) {
+        Py_DECREF(settings);
+        return NULL;
+    }
+
     return settings;
 }
 

Python/ceval_gil.c

@@ -500,9 +500,18 @@ PyEval_ThreadsInitialized(void)
 }
 
 PyStatus
-_PyEval_InitGIL(PyThreadState *tstate)
+_PyEval_InitGIL(PyThreadState *tstate, int own_gil)
 {
     assert(tstate->interp->ceval.gil == NULL);
+    if (!own_gil) {
+        PyInterpreterState *main_interp = _PyInterpreterState_Main();
+        assert(tstate->interp != main_interp);
+        struct _gil_runtime_state *gil = main_interp->ceval.gil;
+        assert(gil_created(gil));
+        tstate->interp->ceval.gil = gil;
+        tstate->interp->ceval.own_gil = 0;
+        return _PyStatus_OK();
+    }
 
     /* XXX per-interpreter GIL */
     struct _gil_runtime_state *gil = &tstate->interp->runtime->ceval.gil;
@@ -512,15 +521,19 @@ _PyEval_InitGIL(PyThreadState *tstate)
            and destroy it. */
         assert(gil_created(gil));
         tstate->interp->ceval.gil = gil;
+        // XXX For now we lie.
+        tstate->interp->ceval.own_gil = 1;
         return _PyStatus_OK();
     }
+    assert(own_gil);
 
     assert(!gil_created(gil));
 
     PyThread_init_thread();
     create_gil(gil);
     assert(gil_created(gil));
     tstate->interp->ceval.gil = gil;
+    tstate->interp->ceval.own_gil = 1;
     take_gil(tstate);
     return _PyStatus_OK();
 }
@@ -530,6 +543,14 @@ _PyEval_FiniGIL(PyInterpreterState *interp)
 {
     if (interp->ceval.gil == NULL) {
         /* It was already finalized (or hasn't been initialized yet). */
+        assert(!interp->ceval.own_gil);
+        return;
+    }
+    else if (!interp->ceval.own_gil) {
+        PyInterpreterState *main_interp = _PyInterpreterState_Main();
+        assert(interp != main_interp);
+        assert(interp->ceval.gil == main_interp->ceval.gil);
+        interp->ceval.gil = NULL;
         return;
     }
 

Python/pylifecycle.c

@@ -585,7 +585,7 @@ init_interp_settings(PyInterpreterState *interp,
 
 
 static PyStatus
-init_interp_create_gil(PyThreadState *tstate)
+init_interp_create_gil(PyThreadState *tstate, int own_gil)
 {
     PyStatus status;
 
@@ -600,7 +600,7 @@ init_interp_create_gil(PyThreadState *tstate)
     }
 
     /* Create the GIL and take it */
-    status = _PyEval_InitGIL(tstate);
+    status = _PyEval_InitGIL(tstate, own_gil);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
     }
@@ -647,7 +647,7 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
     _PyThreadState_Bind(tstate);
     (void) PyThreadState_Swap(tstate);
 
-    status = init_interp_create_gil(tstate);
+    status = init_interp_create_gil(tstate, config.own_gil);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
     }
@@ -2049,7 +2049,7 @@ new_interpreter(PyThreadState **tstate_p, const PyInterpreterConfig *config)
         goto error;
     }
 
-    status = init_interp_create_gil(tstate);
+    status = init_interp_create_gil(tstate, config->own_gil);
     if (_PyStatus_EXCEPTION(status)) {
         goto error;
     }