gh-76785: Add SendChannel.send_buffer() (#110246)

(This is still a test module.)

13 files changed, 467 insertions, 67 deletions

diff --git a/Include/internal/pycore_ceval.h b/Include/internal/pycore_ceval.h
index d3ea3a8..312d67e 100644
--- a/Include/internal/pycore_ceval.h
+++ b/Include/internal/pycore_ceval.h
@@ -41,12 +41,26 @@ extern void _PyEval_InitState(PyInterpreterState *, PyThread_type_lock);
 extern void _PyEval_FiniState(struct _ceval_state *ceval);
 extern void _PyEval_SignalReceived(PyInterpreterState *interp);
 
+// bitwise flags:
+#define _Py_PENDING_MAINTHREADONLY 1
+#define _Py_PENDING_RAWFREE 2
+
 // Export for '_testinternalcapi' shared extension
 PyAPI_FUNC(int) _PyEval_AddPendingCall(
     PyInterpreterState *interp,
     _Py_pending_call_func func,
     void *arg,
-    int mainthreadonly);
+    int flags);
+
+typedef int (*_Py_simple_func)(void *);
+extern int _Py_CallInInterpreter(
+    PyInterpreterState *interp,
+    _Py_simple_func func,
+    void *arg);
+extern int _Py_CallInInterpreterAndRawFree(
+    PyInterpreterState *interp,
+    _Py_simple_func func,
+    void *arg);
 
 extern void _PyEval_SignalAsyncExc(PyInterpreterState *interp);
 #ifdef HAVE_FORK
diff --git a/Include/internal/pycore_ceval_state.h b/Include/internal/pycore_ceval_state.h
index 47971fb..1717ec4 100644
--- a/Include/internal/pycore_ceval_state.h
+++ b/Include/internal/pycore_ceval_state.h
@@ -22,6 +22,7 @@ struct _pending_calls {
     struct _pending_call {
         _Py_pending_call_func func;
         void *arg;
+        int flags;
     } calls[NPENDINGCALLS];
     int first;
     int last;
diff --git a/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h
index 523dfdc..0beddbb 100644
--- a/Include/internal/pycore_interp.h
+++ b/Include/internal/pycore_interp.h
@@ -267,7 +267,8 @@ _PyInterpreterState_SetFinalizing(PyInterpreterState *interp, PyThreadState *tst
 }
 
 
-extern PyInterpreterState* _PyInterpreterState_LookUpID(int64_t);
+// Export for the _xxinterpchannels module.
+PyAPI_FUNC(PyInterpreterState *) _PyInterpreterState_LookUpID(int64_t);
 
 extern int _PyInterpreterState_IDInitref(PyInterpreterState *);
 extern int _PyInterpreterState_IDIncref(PyInterpreterState *);
diff --git a/Include/internal/pycore_pybuffer.h b/Include/internal/pycore_pybuffer.h
new file mode 100644
index 0000000..3cbc290
--- /dev/null
+++ b/Include/internal/pycore_pybuffer.h
@@ -0,0 +1,21 @@
+#ifndef Py_INTERNAL_PYBUFFER_H
+#define Py_INTERNAL_PYBUFFER_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+
+// Exported for the _xxinterpchannels module.
+PyAPI_FUNC(int) _PyBuffer_ReleaseInInterpreter(
+        PyInterpreterState *interp, Py_buffer *view);
+PyAPI_FUNC(int) _PyBuffer_ReleaseInInterpreterAndRawFree(
+        PyInterpreterState *interp, Py_buffer *view);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_PYBUFFER_H */
diff --git a/Lib/test/support/interpreters.py b/Lib/test/support/interpreters.py
index 5aba369..d61724c 100644
--- a/Lib/test/support/interpreters.py
+++ b/Lib/test/support/interpreters.py
@@ -225,6 +225,21 @@ class SendChannel(_ChannelEnd):
         # See bpo-32604 and gh-19829.
         return _channels.send(self._id, obj)
 
+    def send_buffer(self, obj):
+        """Send the object's buffer to the channel's receiving end.
+
+        This blocks until the object is received.
+        """
+        _channels.send_buffer(self._id, obj)
+
+    def send_buffer_nowait(self, obj):
+        """Send the object's buffer to the channel's receiving end.
+
+        If the object is immediately received then return True
+        (else False).  Otherwise this is the same as send().
+        """
+        return _channels.send_buffer(self._id, obj)
+
     def close(self):
         _channels.close(self._id, send=True)
 
diff --git a/Lib/test/test__xxinterpchannels.py b/Lib/test/test__xxinterpchannels.py
index 750cd99..cb69f73 100644
--- a/Lib/test/test__xxinterpchannels.py
+++ b/Lib/test/test__xxinterpchannels.py
@@ -703,6 +703,21 @@ class ChannelTests(TestBase):
                 channels.recv(cid2)
             del cid2
 
+    def test_send_buffer(self):
+        buf = bytearray(b'spamspamspam')
+        cid = channels.create()
+        channels.send_buffer(cid, buf)
+        obj = channels.recv(cid)
+
+        self.assertIsNot(obj, buf)
+        self.assertIsInstance(obj, memoryview)
+        self.assertEqual(obj, buf)
+
+        buf[4:8] = b'eggs'
+        self.assertEqual(obj, buf)
+        obj[4:8] = b'ham.'
+        self.assertEqual(obj, buf)
+
     def test_allowed_types(self):
         cid = channels.create()
         objects = [
diff --git a/Lib/test/test_interpreters.py b/Lib/test/test_interpreters.py
index f2ef172..fe7b14d 100644
--- a/Lib/test/test_interpreters.py
+++ b/Lib/test/test_interpreters.py
@@ -1067,3 +1067,46 @@ class TestSendRecv(TestBase):
         self.assertEqual(obj4, b'spam')
         self.assertEqual(obj5, b'eggs')
         self.assertIs(obj6, default)
+
+    def test_send_buffer(self):
+        buf = bytearray(b'spamspamspam')
+        obj = None
+        rch, sch = interpreters.create_channel()
+
+        def f():
+            nonlocal obj
+            while True:
+                try:
+                    obj = rch.recv()
+                    break
+                except interpreters.ChannelEmptyError:
+                    time.sleep(0.1)
+        t = threading.Thread(target=f)
+        t.start()
+
+        sch.send_buffer(buf)
+        t.join()
+
+        self.assertIsNot(obj, buf)
+        self.assertIsInstance(obj, memoryview)
+        self.assertEqual(obj, buf)
+
+        buf[4:8] = b'eggs'
+        self.assertEqual(obj, buf)
+        obj[4:8] = b'ham.'
+        self.assertEqual(obj, buf)
+
+    def test_send_buffer_nowait(self):
+        buf = bytearray(b'spamspamspam')
+        rch, sch = interpreters.create_channel()
+        sch.send_buffer_nowait(buf)
+        obj = rch.recv()
+
+        self.assertIsNot(obj, buf)
+        self.assertIsInstance(obj, memoryview)
+        self.assertEqual(obj, buf)
+
+        buf[4:8] = b'eggs'
+        self.assertEqual(obj, buf)
+        obj[4:8] = b'ham.'
+        self.assertEqual(obj, buf)
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 40951a8..043000c 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -1791,6 +1791,7 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/internal/pycore_parking_lot.h \
 		$(srcdir)/Include/internal/pycore_pathconfig.h \
 		$(srcdir)/Include/internal/pycore_pyarena.h \
+		$(srcdir)/Include/internal/pycore_pybuffer.h \
 		$(srcdir)/Include/internal/pycore_pyerrors.h \
 		$(srcdir)/Include/internal/pycore_pyhash.h \
 		$(srcdir)/Include/internal/pycore_pylifecycle.h \
diff --git a/Modules/_xxinterpchannelsmodule.c b/Modules/_xxinterpchannelsmodule.c
index d762f44..a1531c5 100644
--- a/Modules/_xxinterpchannelsmodule.c
+++ b/Modules/_xxinterpchannelsmodule.c
@@ -1,8 +1,14 @@
 /* interpreters module */
 /* low-level access to interpreter primitives */
 
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 #include "interpreteridobject.h"
+#include "pycore_pybuffer.h"      // _PyBuffer_ReleaseInInterpreterAndRawFree()
+#include "pycore_interp.h"        // _PyInterpreterState_LookUpID()
 
 
 /*
@@ -76,6 +82,73 @@ API..  The module does not create any objects that are shared globally.
     PyMem_RawFree(VAR)
 
 
+struct xid_class_registry {
+    size_t count;
+#define MAX_XID_CLASSES 5
+    struct {
+        PyTypeObject *cls;
+    } added[MAX_XID_CLASSES];
+};
+
+static int
+register_xid_class(PyTypeObject *cls, crossinterpdatafunc shared,
+                   struct xid_class_registry *classes)
+{
+    int res = _PyCrossInterpreterData_RegisterClass(cls, shared);
+    if (res == 0) {
+        assert(classes->count < MAX_XID_CLASSES);
+        // The class has refs elsewhere, so we need to incref here.
+        classes->added[classes->count].cls = cls;
+        classes->count += 1;
+    }
+    return res;
+}
+
+static void
+clear_xid_class_registry(struct xid_class_registry *classes)
+{
+    while (classes->count > 0) {
+        classes->count -= 1;
+        PyTypeObject *cls = classes->added[classes->count].cls;
+        _PyCrossInterpreterData_UnregisterClass(cls);
+    }
+}
+
+#define XID_IGNORE_EXC 1
+#define XID_FREE 2
+
+static int
+_release_xid_data(_PyCrossInterpreterData *data, int flags)
+{
+    int ignoreexc = flags & XID_IGNORE_EXC;
+    PyObject *exc;
+    if (ignoreexc) {
+        exc = PyErr_GetRaisedException();
+    }
+    int res;
+    if (flags & XID_FREE) {
+        res = _PyCrossInterpreterData_ReleaseAndRawFree(data);
+    }
+    else {
+        res = _PyCrossInterpreterData_Release(data);
+    }
+    if (res < 0) {
+        /* The owning interpreter is already destroyed. */
+        if (ignoreexc) {
+            // XXX Emit a warning?
+            PyErr_Clear();
+        }
+    }
+    if (flags & XID_FREE) {
+        /* Either way, we free the data. */
+    }
+    if (ignoreexc) {
+        PyErr_SetRaisedException(exc);
+    }
+    return res;
+}
+
+
 static PyInterpreterState *
 _get_current_interp(void)
 {
@@ -140,7 +213,8 @@ add_new_exception(PyObject *mod, const char *name, PyObject *base)
     add_new_exception(MOD, MODULE_NAME "." Py_STRINGIFY(NAME), BASE)
 
 static PyTypeObject *
-add_new_type(PyObject *mod, PyType_Spec *spec, crossinterpdatafunc shared)
+add_new_type(PyObject *mod, PyType_Spec *spec, crossinterpdatafunc shared,
+             struct xid_class_registry *classes)
 {
     PyTypeObject *cls = (PyTypeObject *)PyType_FromMetaclass(
                 NULL, mod, spec, NULL);
@@ -152,7 +226,7 @@ add_new_type(PyObject *mod, PyType_Spec *spec, crossinterpdatafunc shared)
         return NULL;
     }
     if (shared != NULL) {
-        if (_PyCrossInterpreterData_RegisterClass(cls, shared)) {
+        if (register_xid_class(cls, shared, classes)) {
             Py_DECREF(cls);
             return NULL;
         }
@@ -160,49 +234,149 @@ add_new_type(PyObject *mod, PyType_Spec *spec, crossinterpdatafunc shared)
     return cls;
 }
 
-#define XID_IGNORE_EXC 1
-#define XID_FREE 2
 
-static int
-_release_xid_data(_PyCrossInterpreterData *data, int flags)
+/* Cross-interpreter Buffer Views *******************************************/
+
+// XXX Release when the original interpreter is destroyed.
+
+typedef struct {
+    PyObject_HEAD
+    Py_buffer *view;
+    int64_t interp;
+} XIBufferViewObject;
+
+static PyObject *
+xibufferview_from_xid(PyTypeObject *cls, _PyCrossInterpreterData *data)
 {
-    int ignoreexc = flags & XID_IGNORE_EXC;
-    PyObject *exc;
-    if (ignoreexc) {
-        exc = PyErr_GetRaisedException();
+    assert(data->data != NULL);
+    assert(data->obj == NULL);
+    assert(data->interp >= 0);
+    XIBufferViewObject *self = PyObject_Malloc(sizeof(XIBufferViewObject));
+    if (self == NULL) {
+        return NULL;
     }
-    int res;
-    if (flags & XID_FREE) {
-        res = _PyCrossInterpreterData_ReleaseAndRawFree(data);
+    PyObject_Init((PyObject *)self, cls);
+    self->view = (Py_buffer *)data->data;
+    self->interp = data->interp;
+    return (PyObject *)self;
+}
+
+static void
+xibufferview_dealloc(XIBufferViewObject *self)
+{
+    PyInterpreterState *interp = _PyInterpreterState_LookUpID(self->interp);
+    /* If the interpreter is no longer alive then we have problems,
+       since other objects may be using the buffer still. */
+    assert(interp != NULL);
+
+    if (_PyBuffer_ReleaseInInterpreterAndRawFree(interp, self->view) < 0) {
+        // XXX Emit a warning?
+        PyErr_Clear();
     }
-    else {
-        res = _PyCrossInterpreterData_Release(data);
+
+    PyTypeObject *tp = Py_TYPE(self);
+    tp->tp_free(self);
+    /* "Instances of heap-allocated types hold a reference to their type."
+     * See: https://docs.python.org/3.11/howto/isolating-extensions.html#garbage-collection-protocol
+     * See: https://docs.python.org/3.11/c-api/typeobj.html#c.PyTypeObject.tp_traverse
+    */
+    // XXX Why don't we implement Py_TPFLAGS_HAVE_GC, e.g. Py_tp_traverse,
+    // like we do for _abc._abc_data?
+    Py_DECREF(tp);
+}
+
+static int
+xibufferview_getbuf(XIBufferViewObject *self, Py_buffer *view, int flags)
+{
+    /* Only PyMemoryView_FromObject() should ever call this,
+       via _memoryview_from_xid() below. */
+    *view = *self->view;
+    view->obj = (PyObject *)self;
+    // XXX Should we leave it alone?
+    view->internal = NULL;
+    return 0;
+}
+
+static PyType_Slot XIBufferViewType_slots[] = {
+    {Py_tp_dealloc, (destructor)xibufferview_dealloc},
+    {Py_bf_getbuffer, (getbufferproc)xibufferview_getbuf},
+    // We don't bother with Py_bf_releasebuffer since we don't need it.
+    {0, NULL},
+};
+
+static PyType_Spec XIBufferViewType_spec = {
+    .name = MODULE_NAME ".CrossInterpreterBufferView",
+    .basicsize = sizeof(XIBufferViewObject),
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_IMMUTABLETYPE),
+    .slots = XIBufferViewType_slots,
+};
+
+
+/* extra XID types **********************************************************/
+
+static PyTypeObject * _get_current_xibufferview_type(void);
+
+static PyObject *
+_memoryview_from_xid(_PyCrossInterpreterData *data)
+{
+    PyTypeObject *cls = _get_current_xibufferview_type();
+    if (cls == NULL) {
+        return NULL;
     }
-    if (res < 0) {
-        /* The owning interpreter is already destroyed. */
-        if (ignoreexc) {
-            // XXX Emit a warning?
-            PyErr_Clear();
-        }
+    PyObject *obj = xibufferview_from_xid(cls, data);
+    if (obj == NULL) {
+        return NULL;
     }
-    if (flags & XID_FREE) {
-        /* Either way, we free the data. */
+    return PyMemoryView_FromObject(obj);
+}
+
+static int
+_memoryview_shared(PyThreadState *tstate, PyObject *obj,
+                   _PyCrossInterpreterData *data)
+{
+    Py_buffer *view = PyMem_RawMalloc(sizeof(Py_buffer));
+    if (view == NULL) {
+        return -1;
     }
-    if (ignoreexc) {
-        PyErr_SetRaisedException(exc);
+    if (PyObject_GetBuffer(obj, view, PyBUF_FULL_RO) < 0) {
+        PyMem_RawFree(view);
+        return -1;
     }
-    return res;
+    _PyCrossInterpreterData_Init(data, tstate->interp, view, NULL,
+                                 _memoryview_from_xid);
+    return 0;
+}
+
+static int
+register_builtin_xid_types(struct xid_class_registry *classes)
+{
+    PyTypeObject *cls;
+    crossinterpdatafunc func;
+
+    // builtin memoryview
+    cls = &PyMemoryView_Type;
+    func = _memoryview_shared;
+    if (register_xid_class(cls, func, classes)) {
+        return -1;
+    }
+
+    return 0;
 }
 
 
 /* module state *************************************************************/
 
 typedef struct {
+    struct xid_class_registry xid_classes;
+
+    /* Added at runtime by interpreters module. */
     PyTypeObject *send_channel_type;
     PyTypeObject *recv_channel_type;
 
     /* heap types */
     PyTypeObject *ChannelIDType;
+    PyTypeObject *XIBufferViewType;
 
     /* exceptions */
     PyObject *ChannelError;
@@ -241,6 +415,7 @@ traverse_module_state(module_state *state, visitproc visit, void *arg)
 {
     /* heap types */
     Py_VISIT(state->ChannelIDType);
+    Py_VISIT(state->XIBufferViewType);
 
     /* exceptions */
     Py_VISIT(state->ChannelError);
@@ -263,6 +438,7 @@ clear_module_state(module_state *state)
         (void)_PyCrossInterpreterData_UnregisterClass(state->ChannelIDType);
     }
     Py_CLEAR(state->ChannelIDType);
+    Py_CLEAR(state->XIBufferViewType);
 
     /* exceptions */
     Py_CLEAR(state->ChannelError);
@@ -275,6 +451,17 @@ clear_module_state(module_state *state)
 }
 
 
+static PyTypeObject *
+_get_current_xibufferview_type(void)
+{
+    module_state *state = _get_current_module_state();
+    if (state == NULL) {
+        return NULL;
+    }
+    return state->XIBufferViewType;
+}
+
+
 /* channel-specific code ****************************************************/
 
 #define CHANNEL_SEND 1
@@ -2045,6 +2232,7 @@ set_channel_end_types(PyObject *mod, PyTypeObject *send, PyTypeObject *recv)
     if (state == NULL) {
         return -1;
     }
+    struct xid_class_registry *xid_classes = &state->xid_classes;
 
     if (state->send_channel_type != NULL
         || state->recv_channel_type != NULL)
@@ -2055,10 +2243,10 @@ set_channel_end_types(PyObject *mod, PyTypeObject *send, PyTypeObject *recv)
     state->send_channel_type = (PyTypeObject *)Py_NewRef(send);
     state->recv_channel_type = (PyTypeObject *)Py_NewRef(recv);
 
-    if (_PyCrossInterpreterData_RegisterClass(send, _channel_end_shared)) {
+    if (register_xid_class(send, _channel_end_shared, xid_classes)) {
         return -1;
     }
-    if (_PyCrossInterpreterData_RegisterClass(recv, _channel_end_shared)) {
+    if (register_xid_class(recv, _channel_end_shared, xid_classes)) {
         return -1;
     }
 
@@ -2326,6 +2514,40 @@ PyDoc_STRVAR(channel_send_doc,
 Add the object's data to the channel's queue.");
 
 static PyObject *
+channel_send_buffer(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    static char *kwlist[] = {"cid", "obj", NULL};
+    int64_t cid;
+    struct channel_id_converter_data cid_data = {
+        .module = self,
+    };
+    PyObject *obj;
+    if (!PyArg_ParseTupleAndKeywords(args, kwds,
+                                     "O&O:channel_send_buffer", kwlist,
+                                     channel_id_converter, &cid_data, &obj)) {
+        return NULL;
+    }
+    cid = cid_data.cid;
+
+    PyObject *tempobj = PyMemoryView_FromObject(obj);
+    if (tempobj == NULL) {
+        return NULL;
+    }
+
+    int err = _channel_send(&_globals.channels, cid, tempobj);
+    Py_DECREF(tempobj);
+    if (handle_channel_error(err, self, cid)) {
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(channel_send_buffer_doc,
+"channel_send_buffer(cid, obj)\n\
+\n\
+Add the object's buffer to the channel's queue.");
+
+static PyObject *
 channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", "default", NULL};
@@ -2516,6 +2738,8 @@ static PyMethodDef module_functions[] = {
      METH_VARARGS | METH_KEYWORDS, channel_list_interpreters_doc},
     {"send",                      _PyCFunction_CAST(channel_send),
      METH_VARARGS | METH_KEYWORDS, channel_send_doc},
+    {"send_buffer",               _PyCFunction_CAST(channel_send_buffer),
+     METH_VARARGS | METH_KEYWORDS, channel_send_buffer_doc},
     {"recv",                      _PyCFunction_CAST(channel_recv),
      METH_VARARGS | METH_KEYWORDS, channel_recv_doc},
     {"close",                     _PyCFunction_CAST(channel_close),
@@ -2543,6 +2767,13 @@ module_exec(PyObject *mod)
     if (_globals_init() != 0) {
         return -1;
     }
+    struct xid_class_registry *xid_classes = NULL;
+
+    module_state *state = get_module_state(mod);
+    if (state == NULL) {
+        goto error;
+    }
+    xid_classes = &state->xid_classes;
 
     /* Add exception types */
     if (exceptions_init(mod) != 0) {
@@ -2550,25 +2781,34 @@ module_exec(PyObject *mod)
     }
 
     /* Add other types */
-    module_state *state = get_module_state(mod);
-    if (state == NULL) {
-        goto error;
-    }
 
     // ChannelID
     state->ChannelIDType = add_new_type(
-            mod, &ChannelIDType_spec, _channelid_shared);
+            mod, &ChannelIDType_spec, _channelid_shared, xid_classes);
     if (state->ChannelIDType == NULL) {
         goto error;
     }
 
-    // Make sure chnnels drop objects owned by this interpreter
+    state->XIBufferViewType = add_new_type(mod, &XIBufferViewType_spec, NULL,
+                                           xid_classes);
+    if (state->XIBufferViewType == NULL) {
+        goto error;
+    }
+
+    if (register_builtin_xid_types(xid_classes) < 0) {
+        goto error;
+    }
+
+    /* Make sure chnnels drop objects owned by this interpreter. */
     PyInterpreterState *interp = _get_current_interp();
     PyUnstable_AtExit(interp, clear_interpreter, (void *)interp);
 
     return 0;
 
 error:
+    if (xid_classes != NULL) {
+        clear_xid_class_registry(xid_classes);
+    }
     _globals_fini();
     return -1;
 }
@@ -2593,6 +2833,11 @@ module_clear(PyObject *mod)
 {
     module_state *state = get_module_state(mod);
     assert(state != NULL);
+
+    // Before clearing anything, we unregister the various XID types. */
+    clear_xid_class_registry(&state->xid_classes);
+
+    // Now we clear the module state.
     clear_module_state(state);
     return 0;
 }
@@ -2602,7 +2847,13 @@ module_free(void *mod)
 {
     module_state *state = get_module_state(mod);
     assert(state != NULL);
+
+    // Before clearing anything, we unregister the various XID types. */
+    clear_xid_class_registry(&state->xid_classes);
+
+    // Now we clear the module state.
     clear_module_state(state);
+
     _globals_fini();
 }
 
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index ac34570..a3c004f 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -315,7 +315,7 @@ trip_signal(int sig_num)
                     _PyEval_AddPendingCall(interp,
                                            report_wakeup_send_error,
                                            (void *)(intptr_t) last_error,
-                                           1);
+                                           _Py_PENDING_MAINTHREADONLY);
                 }
             }
         }
@@ -335,7 +335,7 @@ trip_signal(int sig_num)
                     _PyEval_AddPendingCall(interp,
                                            report_wakeup_write_error,
                                            (void *)(intptr_t)errno,
-                                           1);
+                                           _Py_PENDING_MAINTHREADONLY);
                 }
             }
         }
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 55d3b3a..806ca65 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2,6 +2,7 @@
 
 #include "Python.h"
 #include "pycore_abstract.h"      // _PyIndex_Check()
+#include "pycore_pybuffer.h"
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
 #include "pycore_ceval.h"         // _Py_EnterRecursiveCallTstate()
 #include "pycore_object.h"        // _Py_CheckSlotResult()
@@ -806,6 +807,27 @@ PyBuffer_Release(Py_buffer *view)
     Py_DECREF(obj);
 }
 
+static int
+_buffer_release_call(void *arg)
+{
+    PyBuffer_Release((Py_buffer *)arg);
+    return 0;
+}
+
+int
+_PyBuffer_ReleaseInInterpreter(PyInterpreterState *interp,
+                               Py_buffer *view)
+{
+    return _Py_CallInInterpreter(interp, _buffer_release_call, view);
+}
+
+int
+_PyBuffer_ReleaseInInterpreterAndRawFree(PyInterpreterState *interp,
+                                         Py_buffer *view)
+{
+    return _Py_CallInInterpreterAndRawFree(interp, _buffer_release_call, view);
+}
+
 PyObject *
 PyObject_Format(PyObject *obj, PyObject *format_spec)
 {
diff --git a/Python/ceval_gil.c b/Python/ceval_gil.c
index f237e38..e269efa 100644
--- a/Python/ceval_gil.c
+++ b/Python/ceval_gil.c
@@ -663,7 +663,7 @@ _PyEval_SignalReceived(PyInterpreterState *interp)
 /* Push one item onto the queue while holding the lock. */
 static int
 _push_pending_call(struct _pending_calls *pending,
-                   _Py_pending_call_func func, void *arg)
+                   _Py_pending_call_func func, void *arg, int flags)
 {
     int i = pending->last;
     int j = (i + 1) % NPENDINGCALLS;
@@ -672,6 +672,7 @@ _push_pending_call(struct _pending_calls *pending,
     }
     pending->calls[i].func = func;
     pending->calls[i].arg = arg;
+    pending->calls[i].flags = flags;
     pending->last = j;
     assert(pending->calls_to_do < NPENDINGCALLS);
     pending->calls_to_do++;
@@ -680,7 +681,7 @@ _push_pending_call(struct _pending_calls *pending,
 
 static int
 _next_pending_call(struct _pending_calls *pending,
-                   int (**func)(void *), void **arg)
+                   int (**func)(void *), void **arg, int *flags)
 {
     int i = pending->first;
     if (i == pending->last) {
@@ -690,15 +691,16 @@ _next_pending_call(struct _pending_calls *pending,
     }
     *func = pending->calls[i].func;
     *arg = pending->calls[i].arg;
+    *flags = pending->calls[i].flags;
     return i;
 }
 
 /* Pop one item off the queue while holding the lock. */
 static void
 _pop_pending_call(struct _pending_calls *pending,
-                  int (**func)(void *), void **arg)
+                  int (**func)(void *), void **arg, int *flags)
 {
-    int i = _next_pending_call(pending, func, arg);
+    int i = _next_pending_call(pending, func, arg, flags);
     if (i >= 0) {
         pending->calls[i] = (struct _pending_call){0};
         pending->first = (i + 1) % NPENDINGCALLS;
@@ -714,12 +716,12 @@ _pop_pending_call(struct _pending_calls *pending,
 
 int
 _PyEval_AddPendingCall(PyInterpreterState *interp,
-                       _Py_pending_call_func func, void *arg,
-                       int mainthreadonly)
+                       _Py_pending_call_func func, void *arg, int flags)
 {
-    assert(!mainthreadonly || _Py_IsMainInterpreter(interp));
+    assert(!(flags & _Py_PENDING_MAINTHREADONLY)
+           || _Py_IsMainInterpreter(interp));
     struct _pending_calls *pending = &interp->ceval.pending;
-    if (mainthreadonly) {
+    if (flags & _Py_PENDING_MAINTHREADONLY) {
         /* The main thread only exists in the main interpreter. */
         assert(_Py_IsMainInterpreter(interp));
         pending = &_PyRuntime.ceval.pending_mainthread;
@@ -729,7 +731,7 @@ _PyEval_AddPendingCall(PyInterpreterState *interp,
     assert(pending->lock != NULL);
 
     PyThread_acquire_lock(pending->lock, WAIT_LOCK);
-    int result = _push_pending_call(pending, func, arg);
+    int result = _push_pending_call(pending, func, arg, flags);
     PyThread_release_lock(pending->lock);
 
     /* signal main loop */
@@ -743,7 +745,7 @@ Py_AddPendingCall(_Py_pending_call_func func, void *arg)
     /* Legacy users of this API will continue to target the main thread
        (of the main interpreter). */
     PyInterpreterState *interp = _PyInterpreterState_Main();
-    return _PyEval_AddPendingCall(interp, func, arg, 1);
+    return _PyEval_AddPendingCall(interp, func, arg, _Py_PENDING_MAINTHREADONLY);
 }
 
 static int
@@ -769,17 +771,22 @@ _make_pending_calls(struct _pending_calls *pending)
     for (int i=0; i<NPENDINGCALLS; i++) {
         _Py_pending_call_func func = NULL;
         void *arg = NULL;
+        int flags = 0;
 
         /* pop one item off the queue while holding the lock */
         PyThread_acquire_lock(pending->lock, WAIT_LOCK);
-        _pop_pending_call(pending, &func, &arg);
+        _pop_pending_call(pending, &func, &arg, &flags);
         PyThread_release_lock(pending->lock);
 
         /* having released the lock, perform the callback */
         if (func == NULL) {
             break;
         }
-        if (func(arg) != 0) {
+        int res = func(arg);
+        if ((flags & _Py_PENDING_RAWFREE) && arg != NULL) {
+            PyMem_RawFree(arg);
+        }
+        if (res != 0) {
             return -1;
         }
     }
diff --git a/Python/pystate.c b/Python/pystate.c
index 849a4ee..2086bd6 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2584,18 +2584,36 @@ _PyCrossInterpreterData_NewObject(_PyCrossInterpreterData *data)
     return data->new_object(data);
 }
 
-static int
-_release_xidata_pending(void *data)
+int
+_Py_CallInInterpreter(PyInterpreterState *interp,
+                      _Py_simple_func func, void *arg)
 {
-    _xidata_clear((_PyCrossInterpreterData *)data);
+    if (interp == current_fast_get(interp->runtime)->interp) {
+        return func(arg);
+    }
+    // XXX Emit a warning if this fails?
+    _PyEval_AddPendingCall(interp, (_Py_pending_call_func)func, arg, 0);
+    return 0;
+}
+
+int
+_Py_CallInInterpreterAndRawFree(PyInterpreterState *interp,
+                                _Py_simple_func func, void *arg)
+{
+    if (interp == current_fast_get(interp->runtime)->interp) {
+        int res = func(arg);
+        PyMem_RawFree(arg);
+        return res;
+    }
+    // XXX Emit a warning if this fails?
+    _PyEval_AddPendingCall(interp, func, arg, _Py_PENDING_RAWFREE);
     return 0;
 }
 
 static int
-_xidata_release_and_rawfree_pending(void *data)
+_call_clear_xidata(void *data)
 {
     _xidata_clear((_PyCrossInterpreterData *)data);
-    PyMem_RawFree(data);
     return 0;
 }
 
@@ -2627,21 +2645,12 @@ _xidata_release(_PyCrossInterpreterData *data, int rawfree)
     }
 
     // "Release" the data and/or the object.
-    if (interp == current_fast_get(interp->runtime)->interp) {
-        _xidata_clear(data);
-        if (rawfree) {
-            PyMem_RawFree(data);
-        }
+    if (rawfree) {
+        return _Py_CallInInterpreterAndRawFree(interp, _call_clear_xidata, data);
     }
     else {
-        _Py_pending_call_func func = _release_xidata_pending;
-        if (rawfree) {
-            func = _xidata_release_and_rawfree_pending;
-        }
-        // XXX Emit a warning if this fails?
-        _PyEval_AddPendingCall(interp, func, data, 0);
+        return _Py_CallInInterpreter(interp, _call_clear_xidata, data);
     }
-    return 0;
 }
 
 int