From a77fa0512466bfd6edbab2aa3c830cdd1b0f5ba8 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 17 Oct 2023 17:51:52 -0600
Subject: [PATCH] gh-76785: Clean Up the Channels Module (gh-110568)

---
 Include/cpython/pystate.h         |   2 +-
 Modules/_xxinterpchannelsmodule.c | 616 ++++++++++++++++--------------
 Python/pystate.c                  |  14 +-
 3 files changed, 335 insertions(+), 297 deletions(-)

diff --git a/Include/cpython/pystate.h b/Include/cpython/pystate.h
index 40102f88550..995f02eab58 100644
--- a/Include/cpython/pystate.h
+++ b/Include/cpython/pystate.h
@@ -291,7 +291,7 @@ struct _xid {
     // with deleted interpreters.  Note that IDs are never re-used, so
     // each one will always correspond to a specific interpreter
     // (whether still alive or not).
-    int64_t interp;
+    int64_t interpid;
     // new_object is a function that returns a new object in the current
     // interpreter given the data.  The resulting object (a new
     // reference) will be equivalent to the original object.  This field
diff --git a/Modules/_xxinterpchannelsmodule.c b/Modules/_xxinterpchannelsmodule.c
index 2e2878d5c20..b618592bf00 100644
--- a/Modules/_xxinterpchannelsmodule.c
+++ b/Modules/_xxinterpchannelsmodule.c
@@ -28,7 +28,7 @@ _globals (static struct globals):
         next_id; (int64_t)
         mutex (PyThread_type_lock)
         head (linked list of struct _channelref *):
-            id (int64_t)
+            cid (int64_t)
             objcount (Py_ssize_t)
             next (struct _channelref *):
                 ...
@@ -42,7 +42,7 @@ _globals (static struct globals):
                     numsendopen (int64_t)
                     numrecvopen (int64_t)
                     send (struct _channelend *):
-                        interp (int64_t)
+                        interpid (int64_t)
                         open (int)
                         next (struct _channelend *)
                     recv (struct _channelend *):
@@ -55,7 +55,7 @@ _globals (static struct globals):
                         data (_PyCrossInterpreterData *):
                             data (void *)
                             obj (PyObject *)
-                            interp (int64_t)
+                            interpid (int64_t)
                             new_object (xid_newobjectfunc)
                             free (xid_freefunc)
                     last (struct _channelitem *):
@@ -269,7 +269,7 @@ wait_for_lock(PyThread_type_lock mutex, PY_TIMEOUT_T timeout)
 typedef struct {
     PyObject_HEAD
     Py_buffer *view;
-    int64_t interp;
+    int64_t interpid;
 } XIBufferViewObject;
 
 static PyObject *
@@ -277,21 +277,21 @@ xibufferview_from_xid(PyTypeObject *cls, _PyCrossInterpreterData *data)
 {
     assert(data->data != NULL);
     assert(data->obj == NULL);
-    assert(data->interp >= 0);
+    assert(data->interpid >= 0);
     XIBufferViewObject *self = PyObject_Malloc(sizeof(XIBufferViewObject));
     if (self == NULL) {
         return NULL;
     }
     PyObject_Init((PyObject *)self, cls);
     self->view = (Py_buffer *)data->data;
-    self->interp = data->interp;
+    self->interpid = data->interpid;
     return (PyObject *)self;
 }
 
 static void
 xibufferview_dealloc(XIBufferViewObject *self)
 {
-    PyInterpreterState *interp = _PyInterpreterState_LookUpID(self->interp);
+    PyInterpreterState *interp = _PyInterpreterState_LookUpID(self->interpid);
     /* If the interpreter is no longer alive then we have problems,
        since other objects may be using the buffer still. */
     assert(interp != NULL);
@@ -495,6 +495,7 @@ _get_current_xibufferview_type(void)
 #define CHANNEL_BOTH 0
 #define CHANNEL_RECV -1
 
+
 /* channel errors */
 
 #define ERR_CHANNEL_NOT_FOUND -2
@@ -593,6 +594,7 @@ handle_channel_error(int err, PyObject *mod, int64_t cid)
     return 1;
 }
 
+
 /* the channel queue */
 
 typedef uintptr_t _channelitem_id_t;
@@ -711,7 +713,7 @@ _channelitem_clear(_channelitem *item)
     item->next = NULL;
 
     if (item->data != NULL) {
-        // It was allocated in _channel_send().
+        // It was allocated in channel_send().
         (void)_release_xid_data(item->data, XID_IGNORE_EXC & XID_FREE);
         item->data = NULL;
     }
@@ -911,14 +913,14 @@ _channelqueue_remove(_channelqueue *queue, _channelitem_id_t itemid,
 }
 
 static void
-_channelqueue_drop_interpreter(_channelqueue *queue, int64_t interp)
+_channelqueue_clear_interpreter(_channelqueue *queue, int64_t interpid)
 {
     _channelitem *prev = NULL;
     _channelitem *next = queue->first;
     while (next != NULL) {
         _channelitem *item = next;
         next = item->next;
-        if (item->data->interp == interp) {
+        if (item->data->interpid == interpid) {
             if (prev == NULL) {
                 queue->first = item->next;
             }
@@ -934,18 +936,19 @@ _channelqueue_drop_interpreter(_channelqueue *queue, int64_t interp)
     }
 }
 
+
 /* channel-interpreter associations */
 
 struct _channelend;
 
 typedef struct _channelend {
     struct _channelend *next;
-    int64_t interp;
+    int64_t interpid;
     int open;
 } _channelend;
 
 static _channelend *
-_channelend_new(int64_t interp)
+_channelend_new(int64_t interpid)
 {
     _channelend *end = GLOBAL_MALLOC(_channelend);
     if (end == NULL) {
@@ -953,7 +956,7 @@ _channelend_new(int64_t interp)
         return NULL;
     }
     end->next = NULL;
-    end->interp = interp;
+    end->interpid = interpid;
     end->open = 1;
     return end;
 }
@@ -975,12 +978,12 @@ _channelend_free_all(_channelend *end)
 }
 
 static _channelend *
-_channelend_find(_channelend *first, int64_t interp, _channelend **pprev)
+_channelend_find(_channelend *first, int64_t interpid, _channelend **pprev)
 {
     _channelend *prev = NULL;
     _channelend *end = first;
     while (end != NULL) {
-        if (end->interp == interp) {
+        if (end->interpid == interpid) {
             break;
         }
         prev = end;
@@ -1037,10 +1040,10 @@ _channelends_free(_channelends *ends)
 }
 
 static _channelend *
-_channelends_add(_channelends *ends, _channelend *prev, int64_t interp,
+_channelends_add(_channelends *ends, _channelend *prev, int64_t interpid,
                  int send)
 {
-    _channelend *end = _channelend_new(interp);
+    _channelend *end = _channelend_new(interpid);
     if (end == NULL) {
         return NULL;
     }
@@ -1066,11 +1069,11 @@ _channelends_add(_channelends *ends, _channelend *prev, int64_t interp,
 }
 
 static int
-_channelends_associate(_channelends *ends, int64_t interp, int send)
+_channelends_associate(_channelends *ends, int64_t interpid, int send)
 {
     _channelend *prev;
     _channelend *end = _channelend_find(send ? ends->send : ends->recv,
-                                        interp, &prev);
+                                        interpid, &prev);
     if (end != NULL) {
         if (!end->open) {
             return ERR_CHANNEL_CLOSED;
@@ -1078,7 +1081,7 @@ _channelends_associate(_channelends *ends, int64_t interp, int send)
         // already associated
         return 0;
     }
-    if (_channelends_add(ends, prev, interp, send) == NULL) {
+    if (_channelends_add(ends, prev, interpid, send) == NULL) {
         return -1;
     }
     return 0;
@@ -1088,16 +1091,20 @@ static int
 _channelends_is_open(_channelends *ends)
 {
     if (ends->numsendopen != 0 || ends->numrecvopen != 0) {
+        // At least one interpreter is still associated with the channel
+        // (and hasn't been released).
         return 1;
     }
+    // XXX This is wrong if an end can ever be removed.
     if (ends->send == NULL && ends->recv == NULL) {
+        // The channel has never had any interpreters associated with it.
         return 1;
     }
     return 0;
 }
 
 static void
-_channelends_close_end(_channelends *ends, _channelend *end, int send)
+_channelends_release_end(_channelends *ends, _channelend *end, int send)
 {
     end->open = 0;
     if (send) {
@@ -1109,51 +1116,37 @@ _channelends_close_end(_channelends *ends, _channelend *end, int send)
 }
 
 static int
-_channelends_close_interpreter(_channelends *ends, int64_t interp, int which)
+_channelends_release_interpreter(_channelends *ends, int64_t interpid, int which)
 {
     _channelend *prev;
     _channelend *end;
     if (which >= 0) {  // send/both
-        end = _channelend_find(ends->send, interp, &prev);
+        end = _channelend_find(ends->send, interpid, &prev);
         if (end == NULL) {
             // never associated so add it
-            end = _channelends_add(ends, prev, interp, 1);
+            end = _channelends_add(ends, prev, interpid, 1);
             if (end == NULL) {
                 return -1;
             }
         }
-        _channelends_close_end(ends, end, 1);
+        _channelends_release_end(ends, end, 1);
     }
     if (which <= 0) {  // recv/both
-        end = _channelend_find(ends->recv, interp, &prev);
+        end = _channelend_find(ends->recv, interpid, &prev);
         if (end == NULL) {
             // never associated so add it
-            end = _channelends_add(ends, prev, interp, 0);
+            end = _channelends_add(ends, prev, interpid, 0);
             if (end == NULL) {
                 return -1;
             }
         }
-        _channelends_close_end(ends, end, 0);
+        _channelends_release_end(ends, end, 0);
     }
     return 0;
 }
 
 static void
-_channelends_drop_interpreter(_channelends *ends, int64_t interp)
-{
-    _channelend *end;
-    end = _channelend_find(ends->send, interp, NULL);
-    if (end != NULL) {
-        _channelends_close_end(ends, end, 1);
-    }
-    end = _channelend_find(ends->recv, interp, NULL);
-    if (end != NULL) {
-        _channelends_close_end(ends, end, 0);
-    }
-}
-
-static void
-_channelends_close_all(_channelends *ends, int which, int force)
+_channelends_release_all(_channelends *ends, int which, int force)
 {
     // XXX Handle the ends.
     // XXX Handle force is True.
@@ -1161,16 +1154,32 @@ _channelends_close_all(_channelends *ends, int which, int force)
     // Ensure all the "send"-associated interpreters are closed.
     _channelend *end;
     for (end = ends->send; end != NULL; end = end->next) {
-        _channelends_close_end(ends, end, 1);
+        _channelends_release_end(ends, end, 1);
     }
 
     // Ensure all the "recv"-associated interpreters are closed.
     for (end = ends->recv; end != NULL; end = end->next) {
-        _channelends_close_end(ends, end, 0);
+        _channelends_release_end(ends, end, 0);
     }
 }
 
-/* channels */
+static void
+_channelends_clear_interpreter(_channelends *ends, int64_t interpid)
+{
+    // XXX Actually remove the entries?
+    _channelend *end;
+    end = _channelend_find(ends->send, interpid, NULL);
+    if (end != NULL) {
+        _channelends_release_end(ends, end, 1);
+    }
+    end = _channelend_find(ends->recv, interpid, NULL);
+    if (end != NULL) {
+        _channelends_release_end(ends, end, 0);
+    }
+}
+
+
+/* each channel's state */
 
 struct _channel;
 struct _channel_closing;
@@ -1183,12 +1192,12 @@ typedef struct _channel {
     _channelends *ends;
     int open;
     struct _channel_closing *closing;
-} _PyChannelState;
+} _channel_state;
 
-static _PyChannelState *
+static _channel_state *
 _channel_new(PyThread_type_lock mutex)
 {
-    _PyChannelState *chan = GLOBAL_MALLOC(_PyChannelState);
+    _channel_state *chan = GLOBAL_MALLOC(_channel_state);
     if (chan == NULL) {
         return NULL;
     }
@@ -1210,7 +1219,7 @@ _channel_new(PyThread_type_lock mutex)
 }
 
 static void
-_channel_free(_PyChannelState *chan)
+_channel_free(_channel_state *chan)
 {
     _channel_clear_closing(chan);
     PyThread_acquire_lock(chan->mutex, WAIT_LOCK);
@@ -1223,7 +1232,7 @@ _channel_free(_PyChannelState *chan)
 }
 
 static int
-_channel_add(_PyChannelState *chan, int64_t interp,
+_channel_add(_channel_state *chan, int64_t interpid,
              _PyCrossInterpreterData *data, _waiting_t *waiting)
 {
     int res = -1;
@@ -1233,7 +1242,7 @@ _channel_add(_PyChannelState *chan, int64_t interp,
         res = ERR_CHANNEL_CLOSED;
         goto done;
     }
-    if (_channelends_associate(chan->ends, interp, 1) != 0) {
+    if (_channelends_associate(chan->ends, interpid, 1) != 0) {
         res = ERR_CHANNEL_INTERP_CLOSED;
         goto done;
     }
@@ -1250,7 +1259,7 @@ _channel_add(_PyChannelState *chan, int64_t interp,
 }
 
 static int
-_channel_next(_PyChannelState *chan, int64_t interp,
+_channel_next(_channel_state *chan, int64_t interpid,
               _PyCrossInterpreterData **p_data, _waiting_t **p_waiting)
 {
     int err = 0;
@@ -1260,7 +1269,7 @@ _channel_next(_PyChannelState *chan, int64_t interp,
         err = ERR_CHANNEL_CLOSED;
         goto done;
     }
-    if (_channelends_associate(chan->ends, interp, 0) != 0) {
+    if (_channelends_associate(chan->ends, interpid, 0) != 0) {
         err = ERR_CHANNEL_INTERP_CLOSED;
         goto done;
     }
@@ -1281,7 +1290,7 @@ _channel_next(_PyChannelState *chan, int64_t interp,
 }
 
 static void
-_channel_remove(_PyChannelState *chan, _channelitem_id_t itemid)
+_channel_remove(_channel_state *chan, _channelitem_id_t itemid)
 {
     _PyCrossInterpreterData *data = NULL;
     _waiting_t *waiting = NULL;
@@ -1301,7 +1310,7 @@ _channel_remove(_PyChannelState *chan, _channelitem_id_t itemid)
 }
 
 static int
-_channel_close_interpreter(_PyChannelState *chan, int64_t interp, int end)
+_channel_release_interpreter(_channel_state *chan, int64_t interpid, int end)
 {
     PyThread_acquire_lock(chan->mutex, WAIT_LOCK);
 
@@ -1311,10 +1320,12 @@ _channel_close_interpreter(_PyChannelState *chan, int64_t interp, int end)
         goto done;
     }
 
-    if (_channelends_close_interpreter(chan->ends, interp, end) != 0) {
+    if (_channelends_release_interpreter(chan->ends, interpid, end) != 0) {
         goto done;
     }
     chan->open = _channelends_is_open(chan->ends);
+    // XXX Clear the queue if not empty?
+    // XXX Activate the "closing" mechanism?
 
     res = 0;
 done:
@@ -1322,20 +1333,8 @@ _channel_close_interpreter(_PyChannelState *chan, int64_t interp, int end)
     return res;
 }
 
-static void
-_channel_drop_interpreter(_PyChannelState *chan, int64_t interp)
-{
-    PyThread_acquire_lock(chan->mutex, WAIT_LOCK);
-
-    _channelqueue_drop_interpreter(chan->queue, interp);
-    _channelends_drop_interpreter(chan->ends, interp);
-    chan->open = _channelends_is_open(chan->ends);
-
-    PyThread_release_lock(chan->mutex);
-}
-
 static int
-_channel_close_all(_PyChannelState *chan, int end, int force)
+_channel_release_all(_channel_state *chan, int end, int force)
 {
     int res = -1;
     PyThread_acquire_lock(chan->mutex, WAIT_LOCK);
@@ -1349,12 +1348,13 @@ _channel_close_all(_PyChannelState *chan, int end, int force)
         res = ERR_CHANNEL_NOT_EMPTY;
         goto done;
     }
+    // XXX Clear the queue?
 
     chan->open = 0;
 
     // We *could* also just leave these in place, since we've marked
     // the channel as closed already.
-    _channelends_close_all(chan->ends, end, force);
+    _channelends_release_all(chan->ends, end, force);
 
     res = 0;
 done:
@@ -1362,25 +1362,39 @@ _channel_close_all(_PyChannelState *chan, int end, int force)
     return res;
 }
 
+static void
+_channel_clear_interpreter(_channel_state *chan, int64_t interpid)
+{
+    PyThread_acquire_lock(chan->mutex, WAIT_LOCK);
+
+    _channelqueue_clear_interpreter(chan->queue, interpid);
+    _channelends_clear_interpreter(chan->ends, interpid);
+    chan->open = _channelends_is_open(chan->ends);
+
+    PyThread_release_lock(chan->mutex);
+}
+
+
 /* the set of channels */
 
 struct _channelref;
 
 typedef struct _channelref {
-    int64_t id;
-    _PyChannelState *chan;
+    int64_t cid;
+    _channel_state *chan;
     struct _channelref *next;
+    // The number of ChannelID objects referring to this channel.
     Py_ssize_t objcount;
 } _channelref;
 
 static _channelref *
-_channelref_new(int64_t id, _PyChannelState *chan)
+_channelref_new(int64_t cid, _channel_state *chan)
 {
     _channelref *ref = GLOBAL_MALLOC(_channelref);
     if (ref == NULL) {
         return NULL;
     }
-    ref->id = id;
+    ref->cid = cid;
     ref->chan = chan;
     ref->next = NULL;
     ref->objcount = 0;
@@ -1390,7 +1404,7 @@ _channelref_new(int64_t id, _PyChannelState *chan)
 //static void
 //_channelref_clear(_channelref *ref)
 //{
-//    ref->id = -1;
+//    ref->cid = -1;
 //    ref->chan = NULL;
 //    ref->next = NULL;
 //    ref->objcount = 0;
@@ -1407,12 +1421,12 @@ _channelref_free(_channelref *ref)
 }
 
 static _channelref *
-_channelref_find(_channelref *first, int64_t id, _channelref **pprev)
+_channelref_find(_channelref *first, int64_t cid, _channelref **pprev)
 {
     _channelref *prev = NULL;
     _channelref *ref = first;
     while (ref != NULL) {
-        if (ref->id == id) {
+        if (ref->cid == cid) {
             break;
         }
         prev = ref;
@@ -1424,6 +1438,7 @@ _channelref_find(_channelref *first, int64_t id, _channelref **pprev)
     return ref;
 }
 
+
 typedef struct _channels {
     PyThread_type_lock mutex;
     _channelref *head;
@@ -1454,27 +1469,27 @@ _channels_fini(_channels *channels)
 static int64_t
 _channels_next_id(_channels *channels)  // needs lock
 {
-    int64_t id = channels->next_id;
-    if (id < 0) {
+    int64_t cid = channels->next_id;
+    if (cid < 0) {
         /* overflow */
         return -1;
     }
     channels->next_id += 1;
-    return id;
+    return cid;
 }
 
 static int
-_channels_lookup(_channels *channels, int64_t id, PyThread_type_lock *pmutex,
-                 _PyChannelState **res)
+_channels_lookup(_channels *channels, int64_t cid, PyThread_type_lock *pmutex,
+                 _channel_state **res)
 {
     int err = -1;
-    _PyChannelState *chan = NULL;
+    _channel_state *chan = NULL;
     PyThread_acquire_lock(channels->mutex, WAIT_LOCK);
     if (pmutex != NULL) {
         *pmutex = NULL;
     }
 
-    _channelref *ref = _channelref_find(channels->head, id, NULL);
+    _channelref *ref = _channelref_find(channels->head, cid, NULL);
     if (ref == NULL) {
         err = ERR_CHANNEL_NOT_FOUND;
         goto done;
@@ -1501,18 +1516,18 @@ _channels_lookup(_channels *channels, int64_t id, PyThread_type_lock *pmutex,
 }
 
 static int64_t
-_channels_add(_channels *channels, _PyChannelState *chan)
+_channels_add(_channels *channels, _channel_state *chan)
 {
     int64_t cid = -1;
     PyThread_acquire_lock(channels->mutex, WAIT_LOCK);
 
     // Create a new ref.
-    int64_t id = _channels_next_id(channels);
-    if (id < 0) {
+    int64_t _cid = _channels_next_id(channels);
+    if (_cid < 0) {
         cid = ERR_NO_NEXT_CHANNEL_ID;
         goto done;
     }
-    _channelref *ref = _channelref_new(id, chan);
+    _channelref *ref = _channelref_new(_cid, chan);
     if (ref == NULL) {
         goto done;
     }
@@ -1523,17 +1538,17 @@ _channels_add(_channels *channels, _PyChannelState *chan)
     channels->head = ref;
     channels->numopen += 1;
 
-    cid = id;
+    cid = _cid;
 done:
     PyThread_release_lock(channels->mutex);
     return cid;
 }
 
 /* forward */
-static int _channel_set_closing(struct _channelref *, PyThread_type_lock);
+static int _channel_set_closing(_channelref *, PyThread_type_lock);
 
 static int
-_channels_close(_channels *channels, int64_t cid, _PyChannelState **pchan,
+_channels_close(_channels *channels, int64_t cid, _channel_state **pchan,
                 int end, int force)
 {
     int res = -1;
@@ -1557,7 +1572,7 @@ _channels_close(_channels *channels, int64_t cid, _PyChannelState **pchan,
         goto done;
     }
     else {
-        int err = _channel_close_all(ref->chan, end, force);
+        int err = _channel_release_all(ref->chan, end, force);
         if (err != 0) {
             if (end == CHANNEL_SEND && err == ERR_CHANNEL_NOT_EMPTY) {
                 if (ref->chan->closing != NULL) {
@@ -1599,7 +1614,7 @@ _channels_close(_channels *channels, int64_t cid, _PyChannelState **pchan,
 
 static void
 _channels_remove_ref(_channels *channels, _channelref *ref, _channelref *prev,
-                     _PyChannelState **pchan)
+                     _channel_state **pchan)
 {
     if (ref == channels->head) {
         channels->head = ref->next;
@@ -1616,7 +1631,7 @@ _channels_remove_ref(_channels *channels, _channelref *ref, _channelref *prev,
 }
 
 static int
-_channels_remove(_channels *channels, int64_t id, _PyChannelState **pchan)
+_channels_remove(_channels *channels, int64_t cid, _channel_state **pchan)
 {
     int res = -1;
     PyThread_acquire_lock(channels->mutex, WAIT_LOCK);
@@ -1626,7 +1641,7 @@ _channels_remove(_channels *channels, int64_t id, _PyChannelState **pchan)
     }
 
     _channelref *prev = NULL;
-    _channelref *ref = _channelref_find(channels->head, id, &prev);
+    _channelref *ref = _channelref_find(channels->head, cid, &prev);
     if (ref == NULL) {
         res = ERR_CHANNEL_NOT_FOUND;
         goto done;
@@ -1641,12 +1656,12 @@ _channels_remove(_channels *channels, int64_t id, _PyChannelState **pchan)
 }
 
 static int
-_channels_add_id_object(_channels *channels, int64_t id)
+_channels_add_id_object(_channels *channels, int64_t cid)
 {
     int res = -1;
     PyThread_acquire_lock(channels->mutex, WAIT_LOCK);
 
-    _channelref *ref = _channelref_find(channels->head, id, NULL);
+    _channelref *ref = _channelref_find(channels->head, cid, NULL);
     if (ref == NULL) {
         res = ERR_CHANNEL_NOT_FOUND;
         goto done;
@@ -1660,12 +1675,12 @@ _channels_add_id_object(_channels *channels, int64_t id)
 }
 
 static void
-_channels_drop_id_object(_channels *channels, int64_t id)
+_channels_release_cid_object(_channels *channels, int64_t cid)
 {
     PyThread_acquire_lock(channels->mutex, WAIT_LOCK);
 
     _channelref *prev = NULL;
-    _channelref *ref = _channelref_find(channels->head, id, &prev);
+    _channelref *ref = _channelref_find(channels->head, cid, &prev);
     if (ref == NULL) {
         // Already destroyed.
         goto done;
@@ -1674,7 +1689,7 @@ _channels_drop_id_object(_channels *channels, int64_t id)
 
     // Destroy if no longer used.
     if (ref->objcount == 0) {
-        _PyChannelState *chan = NULL;
+        _channel_state *chan = NULL;
         _channels_remove_ref(channels, ref, prev, &chan);
         if (chan != NULL) {
             _channel_free(chan);
@@ -1696,7 +1711,7 @@ _channels_list_all(_channels *channels, int64_t *count)
     }
     _channelref *ref = channels->head;
     for (int64_t i=0; ref != NULL; ref = ref->next, i++) {
-        ids[i] = ref->id;
+        ids[i] = ref->cid;
     }
     *count = channels->numopen;
 
@@ -1707,29 +1722,30 @@ _channels_list_all(_channels *channels, int64_t *count)
 }
 
 static void
-_channels_drop_interpreter(_channels *channels, int64_t interp)
+_channels_clear_interpreter(_channels *channels, int64_t interpid)
 {
     PyThread_acquire_lock(channels->mutex, WAIT_LOCK);
 
     _channelref *ref = channels->head;
     for (; ref != NULL; ref = ref->next) {
         if (ref->chan != NULL) {
-            _channel_drop_interpreter(ref->chan, interp);
+            _channel_clear_interpreter(ref->chan, interpid);
         }
     }
 
     PyThread_release_lock(channels->mutex);
 }
 
+
 /* support for closing non-empty channels */
 
 struct _channel_closing {
-    struct _channelref *ref;
+    _channelref *ref;
 };
 
 static int
-_channel_set_closing(struct _channelref *ref, PyThread_type_lock mutex) {
-    struct _channel *chan = ref->chan;
+_channel_set_closing(_channelref *ref, PyThread_type_lock mutex) {
+    _channel_state *chan = ref->chan;
     if (chan == NULL) {
         // already closed
         return 0;
@@ -1753,7 +1769,7 @@ _channel_set_closing(struct _channelref *ref, PyThread_type_lock mutex) {
 }
 
 static void
-_channel_clear_closing(struct _channel *chan) {
+_channel_clear_closing(_channel_state *chan) {
     PyThread_acquire_lock(chan->mutex, WAIT_LOCK);
     if (chan->closing != NULL) {
         GLOBAL_FREE(chan->closing);
@@ -1763,7 +1779,7 @@ _channel_clear_closing(struct _channel *chan) {
 }
 
 static void
-_channel_finish_closing(struct _channel *chan) {
+_channel_finish_closing(_channel_state *chan) {
     struct _channel_closing *closing = chan->closing;
     if (closing == NULL) {
         return;
@@ -1775,32 +1791,35 @@ _channel_finish_closing(struct _channel *chan) {
     _channel_free(chan);
 }
 
+
 /* "high"-level channel-related functions */
 
+// Create a new channel.
 static int64_t
-_channel_create(_channels *channels)
+channel_create(_channels *channels)
 {
     PyThread_type_lock mutex = PyThread_allocate_lock();
     if (mutex == NULL) {
         return ERR_CHANNEL_MUTEX_INIT;
     }
-    _PyChannelState *chan = _channel_new(mutex);
+    _channel_state *chan = _channel_new(mutex);
     if (chan == NULL) {
         PyThread_free_lock(mutex);
         return -1;
     }
-    int64_t id = _channels_add(channels, chan);
-    if (id < 0) {
+    int64_t cid = _channels_add(channels, chan);
+    if (cid < 0) {
         _channel_free(chan);
     }
-    return id;
+    return cid;
 }
 
+// Completely destroy the channel.
 static int
-_channel_destroy(_channels *channels, int64_t id)
+channel_destroy(_channels *channels, int64_t cid)
 {
-    _PyChannelState *chan = NULL;
-    int err = _channels_remove(channels, id, &chan);
+    _channel_state *chan = NULL;
+    int err = _channels_remove(channels, cid, &chan);
     if (err != 0) {
         return err;
     }
@@ -1810,19 +1829,23 @@ _channel_destroy(_channels *channels, int64_t id)
     return 0;
 }
 
+// Push an object onto the channel.
+// The current interpreter gets associated with the send end of the channel.
+// Optionally request to be notified when it is received.
 static int
-_channel_send(_channels *channels, int64_t id, PyObject *obj,
-              _waiting_t *waiting)
+channel_send(_channels *channels, int64_t cid, PyObject *obj,
+             _waiting_t *waiting)
 {
     PyInterpreterState *interp = _get_current_interp();
     if (interp == NULL) {
         return -1;
     }
+    int64_t interpid = PyInterpreterState_GetID(interp);
 
     // Look up the channel.
     PyThread_type_lock mutex = NULL;
-    _PyChannelState *chan = NULL;
-    int err = _channels_lookup(channels, id, &mutex, &chan);
+    _channel_state *chan = NULL;
+    int err = _channels_lookup(channels, cid, &mutex, &chan);
     if (err != 0) {
         return err;
     }
@@ -1847,8 +1870,7 @@ _channel_send(_channels *channels, int64_t id, PyObject *obj,
     }
 
     // Add the data to the channel.
-    int res = _channel_add(chan, PyInterpreterState_GetID(interp),
-                           data, waiting);
+    int res = _channel_add(chan, interpid, data, waiting);
     PyThread_release_lock(mutex);
     if (res != 0) {
         // We may chain an exception here:
@@ -1860,12 +1882,13 @@ _channel_send(_channels *channels, int64_t id, PyObject *obj,
     return 0;
 }
 
+// Basically, un-send an object.
 static void
-_channel_clear_sent(_channels *channels, int64_t cid, _waiting_t *waiting)
+channel_clear_sent(_channels *channels, int64_t cid, _waiting_t *waiting)
 {
     // Look up the channel.
     PyThread_type_lock mutex = NULL;
-    _PyChannelState *chan = NULL;
+    _channel_state *chan = NULL;
     int err = _channels_lookup(channels, cid, &mutex, &chan);
     if (err != 0) {
         // The channel was already closed, etc.
@@ -1881,8 +1904,9 @@ _channel_clear_sent(_channels *channels, int64_t cid, _waiting_t *waiting)
     PyThread_release_lock(mutex);
 }
 
+// Like channel_send(), but strictly wait for the object to be received.
 static int
-_channel_send_wait(_channels *channels, int64_t cid, PyObject *obj,
+channel_send_wait(_channels *channels, int64_t cid, PyObject *obj,
                    PY_TIMEOUT_T timeout)
 {
     // We use a stack variable here, so we must ensure that &waiting
@@ -1894,7 +1918,7 @@ _channel_send_wait(_channels *channels, int64_t cid, PyObject *obj,
     }
 
     /* Queue up the object. */
-    int res = _channel_send(channels, cid, obj, &waiting);
+    int res = channel_send(channels, cid, obj, &waiting);
     if (res < 0) {
         assert(waiting.status == WAITING_NO_STATUS);
         goto finally;
@@ -1906,7 +1930,7 @@ _channel_send_wait(_channels *channels, int64_t cid, PyObject *obj,
         _waiting_finish_releasing(&waiting);
         /* The send() call is failing now, so make sure the item
            won't be received. */
-        _channel_clear_sent(channels, cid, &waiting);
+        channel_clear_sent(channels, cid, &waiting);
         assert(waiting.status == WAITING_RELEASED);
         if (!waiting.received) {
             res = -1;
@@ -1932,8 +1956,11 @@ _channel_send_wait(_channels *channels, int64_t cid, PyObject *obj,
     return res;
 }
 
+// Pop the next object off the channel.  Fail if empty.
+// The current interpreter gets associated with the recv end of the channel.
+// XXX Support a "wait" mutex?
 static int
-_channel_recv(_channels *channels, int64_t id, PyObject **res)
+channel_recv(_channels *channels, int64_t cid, PyObject **res)
 {
     int err;
     *res = NULL;
@@ -1946,11 +1973,12 @@ _channel_recv(_channels *channels, int64_t id, PyObject **res)
         }
         return 0;
     }
+    int64_t interpid = PyInterpreterState_GetID(interp);
 
     // Look up the channel.
     PyThread_type_lock mutex = NULL;
-    _PyChannelState *chan = NULL;
-    err = _channels_lookup(channels, id, &mutex, &chan);
+    _channel_state *chan = NULL;
+    err = _channels_lookup(channels, cid, &mutex, &chan);
     if (err != 0) {
         return err;
     }
@@ -1960,8 +1988,7 @@ _channel_recv(_channels *channels, int64_t id, PyObject **res)
     // Pop off the next item from the channel.
     _PyCrossInterpreterData *data = NULL;
     _waiting_t *waiting = NULL;
-    err = _channel_next(chan, PyInterpreterState_GetID(interp), &data,
-                        &waiting);
+    err = _channel_next(chan, interpid, &data, &waiting);
     PyThread_release_lock(mutex);
     if (err != 0) {
         return err;
@@ -1975,14 +2002,14 @@ _channel_recv(_channels *channels, int64_t id, PyObject **res)
     PyObject *obj = _PyCrossInterpreterData_NewObject(data);
     if (obj == NULL) {
         assert(PyErr_Occurred());
-        // It was allocated in _channel_send(), so we free it.
+        // It was allocated in channel_send(), so we free it.
         (void)_release_xid_data(data, XID_IGNORE_EXC | XID_FREE);
         if (waiting != NULL) {
             _waiting_release(waiting, 0);
         }
         return -1;
     }
-    // It was allocated in _channel_send(), so we free it.
+    // It was allocated in channel_send(), so we free it.
     int release_res = _release_xid_data(data, XID_FREE);
     if (release_res < 0) {
         // The source interpreter has been destroyed already.
@@ -2003,40 +2030,49 @@ _channel_recv(_channels *channels, int64_t id, PyObject **res)
     return 0;
 }
 
+// Disallow send/recv for the current interpreter.
+// The channel is marked as closed if no other interpreters
+// are currently associated.
 static int
-_channel_drop(_channels *channels, int64_t id, int send, int recv)
+channel_release(_channels *channels, int64_t cid, int send, int recv)
 {
     PyInterpreterState *interp = _get_current_interp();
     if (interp == NULL) {
         return -1;
     }
+    int64_t interpid = PyInterpreterState_GetID(interp);
 
     // Look up the channel.
     PyThread_type_lock mutex = NULL;
-    _PyChannelState *chan = NULL;
-    int err = _channels_lookup(channels, id, &mutex, &chan);
+    _channel_state *chan = NULL;
+    int err = _channels_lookup(channels, cid, &mutex, &chan);
     if (err != 0) {
         return err;
     }
     // Past this point we are responsible for releasing the mutex.
 
     // Close one or both of the two ends.
-    int res = _channel_close_interpreter(chan, PyInterpreterState_GetID(interp), send-recv);
+    int res = _channel_release_interpreter(chan, interpid, send-recv);
     PyThread_release_lock(mutex);
     return res;
 }
 
+// Close the channel (for all interpreters).  Fail if it's already closed.
+// Close immediately if it's empty.  Otherwise, disallow sending and
+// finally close once empty.  Optionally, immediately clear and close it.
 static int
-_channel_close(_channels *channels, int64_t id, int end, int force)
+channel_close(_channels *channels, int64_t cid, int end, int force)
 {
-    return _channels_close(channels, id, NULL, end, force);
+    return _channels_close(channels, cid, NULL, end, force);
 }
 
+// Return true if the identified interpreter is associated
+// with the given end of the channel.
 static int
-_channel_is_associated(_channels *channels, int64_t cid, int64_t interp,
+channel_is_associated(_channels *channels, int64_t cid, int64_t interpid,
                        int send)
 {
-    _PyChannelState *chan = NULL;
+    _channel_state *chan = NULL;
     int err = _channels_lookup(channels, cid, NULL, &chan);
     if (err != 0) {
         return err;
@@ -2046,16 +2082,17 @@ _channel_is_associated(_channels *channels, int64_t cid, int64_t interp,
     }
 
     _channelend *end = _channelend_find(send ? chan->ends->send : chan->ends->recv,
-                                        interp, NULL);
+                                        interpid, NULL);
 
     return (end != NULL && end->open);
 }
 
+
 /* ChannelID class */
 
 typedef struct channelid {
     PyObject_HEAD
-    int64_t id;
+    int64_t cid;
     int end;
     int resolve;
     _channels *channels;
@@ -2076,7 +2113,7 @@ channel_id_converter(PyObject *arg, void *ptr)
     module_state *state = get_module_state(data->module);
     assert(state != NULL);
     if (PyObject_TypeCheck(arg, state->ChannelIDType)) {
-        cid = ((channelid *)arg)->id;
+        cid = ((channelid *)arg)->cid;
         end = ((channelid *)arg)->end;
     }
     else if (PyIndex_Check(arg)) {
@@ -2111,7 +2148,7 @@ newchannelid(PyTypeObject *cls, int64_t cid, int end, _channels *channels,
     if (self == NULL) {
         return -1;
     }
-    self->id = cid;
+    self->cid = cid;
     self->end = end;
     self->resolve = resolve;
     self->channels = channels;
@@ -2176,22 +2213,22 @@ _channelid_new(PyObject *mod, PyTypeObject *cls,
         end = CHANNEL_RECV;
     }
 
-    PyObject *id = NULL;
+    PyObject *cidobj = NULL;
     int err = newchannelid(cls, cid, end, _global_channels(),
                            force, resolve,
-                           (channelid **)&id);
+                           (channelid **)&cidobj);
     if (handle_channel_error(err, mod, cid)) {
-        assert(id == NULL);
+        assert(cidobj == NULL);
         return NULL;
     }
-    assert(id != NULL);
-    return id;
+    assert(cidobj != NULL);
+    return cidobj;
 }
 
 static void
 channelid_dealloc(PyObject *self)
 {
-    int64_t cid = ((channelid *)self)->id;
+    int64_t cid = ((channelid *)self)->cid;
     _channels *channels = ((channelid *)self)->channels;
 
     PyTypeObject *tp = Py_TYPE(self);
@@ -2204,7 +2241,7 @@ channelid_dealloc(PyObject *self)
     // like we do for _abc._abc_data?
     Py_DECREF(tp);
 
-    _channels_drop_id_object(channels, cid);
+    _channels_release_cid_object(channels, cid);
 }
 
 static PyObject *
@@ -2213,44 +2250,44 @@ channelid_repr(PyObject *self)
     PyTypeObject *type = Py_TYPE(self);
     const char *name = _PyType_Name(type);
 
-    channelid *cid = (channelid *)self;
+    channelid *cidobj = (channelid *)self;
     const char *fmt;
-    if (cid->end == CHANNEL_SEND) {
+    if (cidobj->end == CHANNEL_SEND) {
         fmt = "%s(%" PRId64 ", send=True)";
     }
-    else if (cid->end == CHANNEL_RECV) {
+    else if (cidobj->end == CHANNEL_RECV) {
         fmt = "%s(%" PRId64 ", recv=True)";
     }
     else {
         fmt = "%s(%" PRId64 ")";
     }
-    return PyUnicode_FromFormat(fmt, name, cid->id);
+    return PyUnicode_FromFormat(fmt, name, cidobj->cid);
 }
 
 static PyObject *
 channelid_str(PyObject *self)
 {
-    channelid *cid = (channelid *)self;
-    return PyUnicode_FromFormat("%" PRId64 "", cid->id);
+    channelid *cidobj = (channelid *)self;
+    return PyUnicode_FromFormat("%" PRId64 "", cidobj->cid);
 }
 
 static PyObject *
 channelid_int(PyObject *self)
 {
-    channelid *cid = (channelid *)self;
-    return PyLong_FromLongLong(cid->id);
+    channelid *cidobj = (channelid *)self;
+    return PyLong_FromLongLong(cidobj->cid);
 }
 
 static Py_hash_t
 channelid_hash(PyObject *self)
 {
-    channelid *cid = (channelid *)self;
-    PyObject *id = PyLong_FromLongLong(cid->id);
-    if (id == NULL) {
+    channelid *cidobj = (channelid *)self;
+    PyObject *pyid = PyLong_FromLongLong(cidobj->cid);
+    if (pyid == NULL) {
         return -1;
     }
-    Py_hash_t hash = PyObject_Hash(id);
-    Py_DECREF(id);
+    Py_hash_t hash = PyObject_Hash(pyid);
+    Py_DECREF(pyid);
     return hash;
 }
 
@@ -2276,11 +2313,11 @@ channelid_richcompare(PyObject *self, PyObject *other, int op)
         goto done;
     }
 
-    channelid *cid = (channelid *)self;
+    channelid *cidobj = (channelid *)self;
     int equal;
     if (PyObject_TypeCheck(other, state->ChannelIDType)) {
-        channelid *othercid = (channelid *)other;
-        equal = (cid->end == othercid->end) && (cid->id == othercid->id);
+        channelid *othercidobj = (channelid *)other;
+        equal = (cidobj->end == othercidobj->end) && (cidobj->cid == othercidobj->cid);
     }
     else if (PyLong_Check(other)) {
         /* Fast path */
@@ -2289,10 +2326,10 @@ channelid_richcompare(PyObject *self, PyObject *other, int op)
         if (othercid == -1 && PyErr_Occurred()) {
             goto done;
         }
-        equal = !overflow && (othercid >= 0) && (cid->id == othercid);
+        equal = !overflow && (othercid >= 0) && (cidobj->cid == othercid);
     }
     else if (PyNumber_Check(other)) {
-        PyObject *pyid = PyLong_FromLongLong(cid->id);
+        PyObject *pyid = PyLong_FromLongLong(cidobj->cid);
         if (pyid == NULL) {
             goto done;
         }
@@ -2317,16 +2354,16 @@ channelid_richcompare(PyObject *self, PyObject *other, int op)
     return res;
 }
 
-static PyTypeObject * _get_current_channel_end_type(int end);
+static PyTypeObject * _get_current_channelend_type(int end);
 
 static PyObject *
-_channel_from_cid(PyObject *cid, int end)
+_channelobj_from_cidobj(PyObject *cidobj, int end)
 {
-    PyObject *cls = (PyObject *)_get_current_channel_end_type(end);
+    PyObject *cls = (PyObject *)_get_current_channelend_type(end);
     if (cls == NULL) {
         return NULL;
     }
-    PyObject *chan = PyObject_CallFunctionObjArgs(cls, cid, NULL);
+    PyObject *chan = PyObject_CallFunctionObjArgs(cls, cidobj, NULL);
     Py_DECREF(cls);
     if (chan == NULL) {
         return NULL;
@@ -2335,7 +2372,7 @@ _channel_from_cid(PyObject *cid, int end)
 }
 
 struct _channelid_xid {
-    int64_t id;
+    int64_t cid;
     int end;
     int resolve;
 };
@@ -2357,16 +2394,16 @@ _channelid_from_xid(_PyCrossInterpreterData *data)
     }
 
     // Note that we do not preserve the "resolve" flag.
-    PyObject *cid = NULL;
-    int err = newchannelid(state->ChannelIDType, xid->id, xid->end,
+    PyObject *cidobj = NULL;
+    int err = newchannelid(state->ChannelIDType, xid->cid, xid->end,
                            _global_channels(), 0, 0,
-                           (channelid **)&cid);
+                           (channelid **)&cidobj);
     if (err != 0) {
-        assert(cid == NULL);
-        (void)handle_channel_error(err, mod, xid->id);
+        assert(cidobj == NULL);
+        (void)handle_channel_error(err, mod, xid->cid);
         goto done;
     }
-    assert(cid != NULL);
+    assert(cidobj != NULL);
     if (xid->end == 0) {
         goto done;
     }
@@ -2375,17 +2412,17 @@ _channelid_from_xid(_PyCrossInterpreterData *data)
     }
 
     /* Try returning a high-level channel end but fall back to the ID. */
-    PyObject *chan = _channel_from_cid(cid, xid->end);
+    PyObject *chan = _channelobj_from_cidobj(cidobj, xid->end);
     if (chan == NULL) {
         PyErr_Clear();
         goto done;
     }
-    Py_DECREF(cid);
-    cid = chan;
+    Py_DECREF(cidobj);
+    cidobj = chan;
 
 done:
     Py_DECREF(mod);
-    return cid;
+    return cidobj;
 }
 
 static int
@@ -2400,7 +2437,7 @@ _channelid_shared(PyThreadState *tstate, PyObject *obj,
         return -1;
     }
     struct _channelid_xid *xid = (struct _channelid_xid *)data->data;
-    xid->id = ((channelid *)obj)->id;
+    xid->cid = ((channelid *)obj)->cid;
     xid->end = ((channelid *)obj)->end;
     xid->resolve = ((channelid *)obj)->resolve;
     return 0;
@@ -2410,30 +2447,30 @@ static PyObject *
 channelid_end(PyObject *self, void *end)
 {
     int force = 1;
-    channelid *cid = (channelid *)self;
+    channelid *cidobj = (channelid *)self;
     if (end != NULL) {
-        PyObject *id = NULL;
-        int err = newchannelid(Py_TYPE(self), cid->id, *(int *)end,
-                               cid->channels, force, cid->resolve,
-                               (channelid **)&id);
+        PyObject *obj = NULL;
+        int err = newchannelid(Py_TYPE(self), cidobj->cid, *(int *)end,
+                               cidobj->channels, force, cidobj->resolve,
+                               (channelid **)&obj);
         if (err != 0) {
-            assert(id == NULL);
+            assert(obj == NULL);
             PyObject *mod = get_module_from_type(Py_TYPE(self));
             if (mod == NULL) {
                 return NULL;
             }
-            (void)handle_channel_error(err, mod, cid->id);
+            (void)handle_channel_error(err, mod, cidobj->cid);
             Py_DECREF(mod);
             return NULL;
         }
-        assert(id != NULL);
-        return id;
+        assert(obj != NULL);
+        return obj;
     }
 
-    if (cid->end == CHANNEL_SEND) {
+    if (cidobj->end == CHANNEL_SEND) {
         return PyUnicode_InternFromString("send");
     }
-    if (cid->end == CHANNEL_RECV) {
+    if (cidobj->end == CHANNEL_RECV) {
         return PyUnicode_InternFromString("recv");
     }
     return PyUnicode_InternFromString("both");
@@ -2455,7 +2492,7 @@ static PyGetSetDef channelid_getsets[] = {
 PyDoc_STRVAR(channelid_doc,
 "A channel ID identifies a channel and may be used as an int.");
 
-static PyType_Slot ChannelIDType_slots[] = {
+static PyType_Slot channelid_typeslots[] = {
     {Py_tp_dealloc, (destructor)channelid_dealloc},
     {Py_tp_doc, (void *)channelid_doc},
     {Py_tp_repr, (reprfunc)channelid_repr},
@@ -2469,12 +2506,12 @@ static PyType_Slot ChannelIDType_slots[] = {
     {0, NULL},
 };
 
-static PyType_Spec ChannelIDType_spec = {
+static PyType_Spec channelid_typespec = {
     .name = MODULE_NAME ".ChannelID",
     .basicsize = sizeof(channelid),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
               Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_IMMUTABLETYPE),
-    .slots = ChannelIDType_slots,
+    .slots = channelid_typeslots,
 };
 
 
@@ -2483,7 +2520,7 @@ static PyType_Spec ChannelIDType_spec = {
 // XXX Use a new __xid__ protocol instead?
 
 static PyTypeObject *
-_get_current_channel_end_type(int end)
+_get_current_channelend_type(int end)
 {
     module_state *state = _get_current_module_state();
     if (state == NULL) {
@@ -2519,24 +2556,24 @@ _get_current_channel_end_type(int end)
 }
 
 static PyObject *
-_channel_end_from_xid(_PyCrossInterpreterData *data)
+_channelend_from_xid(_PyCrossInterpreterData *data)
 {
-    channelid *cid = (channelid *)_channelid_from_xid(data);
-    if (cid == NULL) {
+    channelid *cidobj = (channelid *)_channelid_from_xid(data);
+    if (cidobj == NULL) {
         return NULL;
     }
-    PyTypeObject *cls = _get_current_channel_end_type(cid->end);
+    PyTypeObject *cls = _get_current_channelend_type(cidobj->end);
     if (cls == NULL) {
-        Py_DECREF(cid);
+        Py_DECREF(cidobj);
         return NULL;
     }
-    PyObject *obj = PyObject_CallOneArg((PyObject *)cls, (PyObject *)cid);
-    Py_DECREF(cid);
+    PyObject *obj = PyObject_CallOneArg((PyObject *)cls, (PyObject *)cidobj);
+    Py_DECREF(cidobj);
     return obj;
 }
 
 static int
-_channel_end_shared(PyThreadState *tstate, PyObject *obj,
+_channelend_shared(PyThreadState *tstate, PyObject *obj,
                     _PyCrossInterpreterData *data)
 {
     PyObject *cidobj = PyObject_GetAttrString(obj, "_id");
@@ -2548,12 +2585,12 @@ _channel_end_shared(PyThreadState *tstate, PyObject *obj,
     if (res < 0) {
         return -1;
     }
-    data->new_object = _channel_end_from_xid;
+    data->new_object = _channelend_from_xid;
     return 0;
 }
 
 static int
-set_channel_end_types(PyObject *mod, PyTypeObject *send, PyTypeObject *recv)
+set_channelend_types(PyObject *mod, PyTypeObject *send, PyTypeObject *recv)
 {
     module_state *state = get_module_state(mod);
     if (state == NULL) {
@@ -2570,16 +2607,17 @@ 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 (register_xid_class(send, _channel_end_shared, xid_classes)) {
+    if (register_xid_class(send, _channelend_shared, xid_classes)) {
         return -1;
     }
-    if (register_xid_class(recv, _channel_end_shared, xid_classes)) {
+    if (register_xid_class(recv, _channelend_shared, xid_classes)) {
         return -1;
     }
 
     return 0;
 }
 
+
 /* module level code ********************************************************/
 
 /* globals is the process-global state for the module.  It holds all
@@ -2635,15 +2673,15 @@ clear_interpreter(void *data)
     }
     PyInterpreterState *interp = (PyInterpreterState *)data;
     assert(interp == _get_current_interp());
-    int64_t id = PyInterpreterState_GetID(interp);
-    _channels_drop_interpreter(&_globals.channels, id);
+    int64_t interpid = PyInterpreterState_GetID(interp);
+    _channels_clear_interpreter(&_globals.channels, interpid);
 }
 
 
 static PyObject *
-channel_create(PyObject *self, PyObject *Py_UNUSED(ignored))
+channelsmod_create(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
-    int64_t cid = _channel_create(&_globals.channels);
+    int64_t cid = channel_create(&_globals.channels);
     if (cid < 0) {
         (void)handle_channel_error(-1, self, cid);
         return NULL;
@@ -2652,30 +2690,30 @@ channel_create(PyObject *self, PyObject *Py_UNUSED(ignored))
     if (state == NULL) {
         return NULL;
     }
-    PyObject *id = NULL;
+    PyObject *cidobj = NULL;
     int err = newchannelid(state->ChannelIDType, cid, 0,
                            &_globals.channels, 0, 0,
-                           (channelid **)&id);
+                           (channelid **)&cidobj);
     if (handle_channel_error(err, self, cid)) {
-        assert(id == NULL);
-        err = _channel_destroy(&_globals.channels, cid);
+        assert(cidobj == NULL);
+        err = channel_destroy(&_globals.channels, cid);
         if (handle_channel_error(err, self, cid)) {
             // XXX issue a warning?
         }
         return NULL;
     }
-    assert(id != NULL);
-    assert(((channelid *)id)->channels != NULL);
-    return id;
+    assert(cidobj != NULL);
+    assert(((channelid *)cidobj)->channels != NULL);
+    return cidobj;
 }
 
-PyDoc_STRVAR(channel_create_doc,
+PyDoc_STRVAR(channelsmod_create_doc,
 "channel_create() -> cid\n\
 \n\
 Create a new cross-interpreter channel and return a unique generated ID.");
 
 static PyObject *
-channel_destroy(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_destroy(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", NULL};
     int64_t cid;
@@ -2688,21 +2726,21 @@ channel_destroy(PyObject *self, PyObject *args, PyObject *kwds)
     }
     cid = cid_data.cid;
 
-    int err = _channel_destroy(&_globals.channels, cid);
+    int err = channel_destroy(&_globals.channels, cid);
     if (handle_channel_error(err, self, cid)) {
         return NULL;
     }
     Py_RETURN_NONE;
 }
 
-PyDoc_STRVAR(channel_destroy_doc,
+PyDoc_STRVAR(channelsmod_destroy_doc,
 "channel_destroy(cid)\n\
 \n\
 Close and finalize the channel.  Afterward attempts to use the channel\n\
 will behave as though it never existed.");
 
 static PyObject *
-channel_list_all(PyObject *self, PyObject *Py_UNUSED(ignored))
+channelsmod_list_all(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     int64_t count = 0;
     int64_t *cids = _channels_list_all(&_globals.channels, &count);
@@ -2724,17 +2762,17 @@ channel_list_all(PyObject *self, PyObject *Py_UNUSED(ignored))
     }
     int64_t *cur = cids;
     for (int64_t i=0; i < count; cur++, i++) {
-        PyObject *id = NULL;
+        PyObject *cidobj = NULL;
         int err = newchannelid(state->ChannelIDType, *cur, 0,
                                &_globals.channels, 0, 0,
-                               (channelid **)&id);
+                               (channelid **)&cidobj);
         if (handle_channel_error(err, self, *cur)) {
-            assert(id == NULL);
+            assert(cidobj == NULL);
             Py_SETREF(ids, NULL);
             break;
         }
-        assert(id != NULL);
-        PyList_SET_ITEM(ids, (Py_ssize_t)i, id);
+        assert(cidobj != NULL);
+        PyList_SET_ITEM(ids, (Py_ssize_t)i, cidobj);
     }
 
 finally:
@@ -2742,13 +2780,13 @@ channel_list_all(PyObject *self, PyObject *Py_UNUSED(ignored))
     return ids;
 }
 
-PyDoc_STRVAR(channel_list_all_doc,
+PyDoc_STRVAR(channelsmod_list_all_doc,
 "channel_list_all() -> [cid]\n\
 \n\
 Return the list of all IDs for active channels.");
 
 static PyObject *
-channel_list_interpreters(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_list_interpreters(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", "send", NULL};
     int64_t cid;            /* Channel ID */
@@ -2756,8 +2794,8 @@ channel_list_interpreters(PyObject *self, PyObject *args, PyObject *kwds)
         .module = self,
     };
     int send = 0;           /* Send or receive end? */
-    int64_t id;
-    PyObject *ids, *id_obj;
+    int64_t interpid;
+    PyObject *ids, *interpid_obj;
     PyInterpreterState *interp;
 
     if (!PyArg_ParseTupleAndKeywords(
@@ -2774,20 +2812,20 @@ channel_list_interpreters(PyObject *self, PyObject *args, PyObject *kwds)
 
     interp = PyInterpreterState_Head();
     while (interp != NULL) {
-        id = PyInterpreterState_GetID(interp);
-        assert(id >= 0);
-        int res = _channel_is_associated(&_globals.channels, cid, id, send);
+        interpid = PyInterpreterState_GetID(interp);
+        assert(interpid >= 0);
+        int res = channel_is_associated(&_globals.channels, cid, interpid, send);
         if (res < 0) {
             (void)handle_channel_error(res, self, cid);
             goto except;
         }
         if (res) {
-            id_obj = PyInterpreterState_GetIDObject(interp);
-            if (id_obj == NULL) {
+            interpid_obj = PyInterpreterState_GetIDObject(interp);
+            if (interpid_obj == NULL) {
                 goto except;
             }
-            res = PyList_Insert(ids, 0, id_obj);
-            Py_DECREF(id_obj);
+            res = PyList_Insert(ids, 0, interpid_obj);
+            Py_DECREF(interpid_obj);
             if (res < 0) {
                 goto except;
             }
@@ -2804,7 +2842,7 @@ channel_list_interpreters(PyObject *self, PyObject *args, PyObject *kwds)
     return ids;
 }
 
-PyDoc_STRVAR(channel_list_interpreters_doc,
+PyDoc_STRVAR(channelsmod_list_interpreters_doc,
 "channel_list_interpreters(cid, *, send) -> [id]\n\
 \n\
 Return the list of all interpreter IDs associated with an end of the channel.\n\
@@ -2814,7 +2852,7 @@ receive end.");
 
 
 static PyObject *
-channel_send(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_send(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", "obj", "blocking", "timeout", NULL};
     struct channel_id_converter_data cid_data = {
@@ -2838,10 +2876,10 @@ channel_send(PyObject *self, PyObject *args, PyObject *kwds)
     /* Queue up the object. */
     int err = 0;
     if (blocking) {
-        err = _channel_send_wait(&_globals.channels, cid, obj, timeout);
+        err = channel_send_wait(&_globals.channels, cid, obj, timeout);
     }
     else {
-        err = _channel_send(&_globals.channels, cid, obj, NULL);
+        err = channel_send(&_globals.channels, cid, obj, NULL);
     }
     if (handle_channel_error(err, self, cid)) {
         return NULL;
@@ -2850,14 +2888,14 @@ channel_send(PyObject *self, PyObject *args, PyObject *kwds)
     Py_RETURN_NONE;
 }
 
-PyDoc_STRVAR(channel_send_doc,
+PyDoc_STRVAR(channelsmod_send_doc,
 "channel_send(cid, obj, blocking=True)\n\
 \n\
 Add the object's data to the channel's queue.\n\
 By default this waits for the object to be received.");
 
 static PyObject *
-channel_send_buffer(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_send_buffer(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", "obj", "blocking", "timeout", NULL};
     struct channel_id_converter_data cid_data = {
@@ -2887,10 +2925,10 @@ channel_send_buffer(PyObject *self, PyObject *args, PyObject *kwds)
     /* Queue up the object. */
     int err = 0;
     if (blocking) {
-        err = _channel_send_wait(&_globals.channels, cid, tempobj, timeout);
+        err = channel_send_wait(&_globals.channels, cid, tempobj, timeout);
     }
     else {
-        err = _channel_send(&_globals.channels, cid, tempobj, NULL);
+        err = channel_send(&_globals.channels, cid, tempobj, NULL);
     }
     Py_DECREF(tempobj);
     if (handle_channel_error(err, self, cid)) {
@@ -2900,14 +2938,14 @@ channel_send_buffer(PyObject *self, PyObject *args, PyObject *kwds)
     Py_RETURN_NONE;
 }
 
-PyDoc_STRVAR(channel_send_buffer_doc,
+PyDoc_STRVAR(channelsmod_send_buffer_doc,
 "channel_send_buffer(cid, obj, blocking=True)\n\
 \n\
 Add the object's buffer to the channel's queue.\n\
 By default this waits for the object to be received.");
 
 static PyObject *
-channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_recv(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", "default", NULL};
     int64_t cid;
@@ -2922,7 +2960,7 @@ channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
     cid = cid_data.cid;
 
     PyObject *obj = NULL;
-    int err = _channel_recv(&_globals.channels, cid, &obj);
+    int err = channel_recv(&_globals.channels, cid, &obj);
     if (handle_channel_error(err, self, cid)) {
         return NULL;
     }
@@ -2939,7 +2977,7 @@ channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
     return obj;
 }
 
-PyDoc_STRVAR(channel_recv_doc,
+PyDoc_STRVAR(channelsmod_recv_doc,
 "channel_recv(cid, [default]) -> obj\n\
 \n\
 Return a new object from the data at the front of the channel's queue.\n\
@@ -2948,7 +2986,7 @@ If there is nothing to receive then raise ChannelEmptyError, unless\n\
 a default value is provided.  In that case return it.");
 
 static PyObject *
-channel_close(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_close(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"cid", "send", "recv", "force", NULL};
     int64_t cid;
@@ -2966,14 +3004,14 @@ channel_close(PyObject *self, PyObject *args, PyObject *kwds)
     }
     cid = cid_data.cid;
 
-    int err = _channel_close(&_globals.channels, cid, send-recv, force);
+    int err = channel_close(&_globals.channels, cid, send-recv, force);
     if (handle_channel_error(err, self, cid)) {
         return NULL;
     }
     Py_RETURN_NONE;
 }
 
-PyDoc_STRVAR(channel_close_doc,
+PyDoc_STRVAR(channelsmod_close_doc,
 "channel_close(cid, *, send=None, recv=None, force=False)\n\
 \n\
 Close the channel for all interpreters.\n\
@@ -3001,7 +3039,7 @@ Once the channel's ID has no more ref counts in any interpreter\n\
 the channel will be destroyed.");
 
 static PyObject *
-channel_release(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod_release(PyObject *self, PyObject *args, PyObject *kwds)
 {
     // Note that only the current interpreter is affected.
     static char *kwlist[] = {"cid", "send", "recv", "force", NULL};
@@ -3027,14 +3065,14 @@ channel_release(PyObject *self, PyObject *args, PyObject *kwds)
     // XXX Handle force is True.
     // XXX Fix implicit release.
 
-    int err = _channel_drop(&_globals.channels, cid, send, recv);
+    int err = channel_release(&_globals.channels, cid, send, recv);
     if (handle_channel_error(err, self, cid)) {
         return NULL;
     }
     Py_RETURN_NONE;
 }
 
-PyDoc_STRVAR(channel_release_doc,
+PyDoc_STRVAR(channelsmod_release_doc,
 "channel_release(cid, *, send=None, recv=None, force=True)\n\
 \n\
 Close the channel for the current interpreter.  'send' and 'recv'\n\
@@ -3042,7 +3080,7 @@ Close the channel for the current interpreter.  'send' and 'recv'\n\
 ends are closed.  Closing an already closed end is a noop.");
 
 static PyObject *
-channel__channel_id(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod__channel_id(PyObject *self, PyObject *args, PyObject *kwds)
 {
     module_state *state = get_module_state(self);
     if (state == NULL) {
@@ -3058,7 +3096,7 @@ channel__channel_id(PyObject *self, PyObject *args, PyObject *kwds)
 }
 
 static PyObject *
-channel__register_end_types(PyObject *self, PyObject *args, PyObject *kwds)
+channelsmod__register_end_types(PyObject *self, PyObject *args, PyObject *kwds)
 {
     static char *kwlist[] = {"send", "recv", NULL};
     PyObject *send;
@@ -3079,7 +3117,7 @@ channel__register_end_types(PyObject *self, PyObject *args, PyObject *kwds)
     PyTypeObject *cls_send = (PyTypeObject *)send;
     PyTypeObject *cls_recv = (PyTypeObject *)recv;
 
-    if (set_channel_end_types(self, cls_send, cls_recv) < 0) {
+    if (set_channelend_types(self, cls_send, cls_recv) < 0) {
         return NULL;
     }
 
@@ -3087,27 +3125,27 @@ channel__register_end_types(PyObject *self, PyObject *args, PyObject *kwds)
 }
 
 static PyMethodDef module_functions[] = {
-    {"create",                    channel_create,
-     METH_NOARGS, channel_create_doc},
-    {"destroy",                   _PyCFunction_CAST(channel_destroy),
-     METH_VARARGS | METH_KEYWORDS, channel_destroy_doc},
-    {"list_all",                  channel_list_all,
-     METH_NOARGS, channel_list_all_doc},
-    {"list_interpreters",         _PyCFunction_CAST(channel_list_interpreters),
-     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),
-     METH_VARARGS | METH_KEYWORDS, channel_close_doc},
-    {"release",                   _PyCFunction_CAST(channel_release),
-     METH_VARARGS | METH_KEYWORDS, channel_release_doc},
-    {"_channel_id",               _PyCFunction_CAST(channel__channel_id),
+    {"create",                     channelsmod_create,
+     METH_NOARGS,                  channelsmod_create_doc},
+    {"destroy",                    _PyCFunction_CAST(channelsmod_destroy),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_destroy_doc},
+    {"list_all",                   channelsmod_list_all,
+     METH_NOARGS,                  channelsmod_list_all_doc},
+    {"list_interpreters",          _PyCFunction_CAST(channelsmod_list_interpreters),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_list_interpreters_doc},
+    {"send",                       _PyCFunction_CAST(channelsmod_send),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_send_doc},
+    {"send_buffer",                _PyCFunction_CAST(channelsmod_send_buffer),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_send_buffer_doc},
+    {"recv",                       _PyCFunction_CAST(channelsmod_recv),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_recv_doc},
+    {"close",                      _PyCFunction_CAST(channelsmod_close),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_close_doc},
+    {"release",                    _PyCFunction_CAST(channelsmod_release),
+     METH_VARARGS | METH_KEYWORDS, channelsmod_release_doc},
+    {"_channel_id",                _PyCFunction_CAST(channelsmod__channel_id),
      METH_VARARGS | METH_KEYWORDS, NULL},
-    {"_register_end_types",       _PyCFunction_CAST(channel__register_end_types),
+    {"_register_end_types",        _PyCFunction_CAST(channelsmod__register_end_types),
      METH_VARARGS | METH_KEYWORDS, NULL},
 
     {NULL,                        NULL}           /* sentinel */
@@ -3143,7 +3181,7 @@ module_exec(PyObject *mod)
 
     // ChannelID
     state->ChannelIDType = add_new_type(
-            mod, &ChannelIDType_spec, _channelid_shared, xid_classes);
+            mod, &channelid_typespec, _channelid_shared, xid_classes);
     if (state->ChannelIDType == NULL) {
         goto error;
     }
diff --git a/Python/pystate.c b/Python/pystate.c
index 92cf741f4ca..2e6f07e6003 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2428,7 +2428,7 @@ _xidata_init(_PyCrossInterpreterData *data)
     assert(data->data == NULL);
     assert(data->obj == NULL);
     *data = (_PyCrossInterpreterData){0};
-    data->interp = -1;
+    data->interpid = -1;
 }
 
 static inline void
@@ -2465,7 +2465,7 @@ _PyCrossInterpreterData_Init(_PyCrossInterpreterData *data,
     // Ideally every object would know its owning interpreter.
     // Until then, we have to rely on the caller to identify it
     // (but we don't need it in all cases).
-    data->interp = (interp != NULL) ? interp->id : -1;
+    data->interpid = (interp != NULL) ? interp->id : -1;
     data->new_object = new_object;
 }
 
@@ -2494,7 +2494,7 @@ _PyCrossInterpreterData_Clear(PyInterpreterState *interp,
 {
     assert(data != NULL);
     // This must be called in the owning interpreter.
-    assert(interp == NULL || data->interp == interp->id);
+    assert(interp == NULL || data->interpid == interp->id);
     _xidata_clear(data);
 }
 
@@ -2505,7 +2505,7 @@ _check_xidata(PyThreadState *tstate, _PyCrossInterpreterData *data)
 
     // data->obj may be NULL, so we don't check it.
 
-    if (data->interp < 0) {
+    if (data->interpid < 0) {
         _PyErr_SetString(tstate, PyExc_SystemError, "missing interp");
         return -1;
     }
@@ -2557,7 +2557,7 @@ _PyObject_GetCrossInterpreterData(PyObject *obj, _PyCrossInterpreterData *data)
 
     // Reset data before re-populating.
     *data = (_PyCrossInterpreterData){0};
-    data->interp = -1;
+    data->interpid = -1;
 
     // Call the "getdata" func for the object.
     Py_INCREF(obj);
@@ -2573,7 +2573,7 @@ _PyObject_GetCrossInterpreterData(PyObject *obj, _PyCrossInterpreterData *data)
     }
 
     // Fill in the blanks and validate the result.
-    data->interp = interp->id;
+    data->interpid = interp->id;
     if (_check_xidata(tstate, data) != 0) {
         (void)_PyCrossInterpreterData_Release(data);
         return -1;
@@ -2636,7 +2636,7 @@ _xidata_release(_PyCrossInterpreterData *data, int rawfree)
     }
 
     // Switch to the original interpreter.
-    PyInterpreterState *interp = _PyInterpreterState_LookUpID(data->interp);
+    PyInterpreterState *interp = _PyInterpreterState_LookUpID(data->interpid);
     if (interp == NULL) {
         // The interpreter was already destroyed.
         // This function shouldn't have been called.