py/scheduler: Rename sched_stack to sched_queue.

Behaviour was changed from stack to queue in
8977c7eb, and this updates variable names
to match.  Also updates other references (docs, error messages).

docs/library/micropython.rst

@@ -136,5 +136,5 @@ Functions
    :ref:`reference documentation <isr_rules>` under "Creation of Python
    objects".
 
-   There is a finite stack to hold the scheduled functions and `schedule()`
-   will raise a `RuntimeError` if the stack is full.
+   There is a finite queue to hold the scheduled functions and `schedule()`
+   will raise a `RuntimeError` if the queue is full.

py/modmicropython.c

@@ -150,7 +150,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_micropython_kbd_intr_obj, mp_micropython_kbd
 #if MICROPY_ENABLE_SCHEDULER
 STATIC mp_obj_t mp_micropython_schedule(mp_obj_t function, mp_obj_t arg) {
     if (!mp_sched_schedule(function, arg)) {
-        mp_raise_msg(&mp_type_RuntimeError, "schedule stack full");
+        mp_raise_msg(&mp_type_RuntimeError, "schedule queue full");
     }
     return mp_const_none;
 }

py/mpstate.h

@@ -141,7 +141,7 @@ typedef struct _mp_state_vm_t {
     volatile mp_obj_t mp_pending_exception;
 
     #if MICROPY_ENABLE_SCHEDULER
-    mp_sched_item_t sched_stack[MICROPY_SCHEDULER_DEPTH];
+    mp_sched_item_t sched_queue[MICROPY_SCHEDULER_DEPTH];
     #endif
 
     // current exception being handled, for sys.exc_info()

py/scheduler.c

@@ -65,7 +65,7 @@ void mp_handle_pending(void) {
 void mp_handle_pending_tail(mp_uint_t atomic_state) {
     MP_STATE_VM(sched_state) = MP_SCHED_LOCKED;
     if (!mp_sched_empty()) {
-        mp_sched_item_t item = MP_STATE_VM(sched_stack)[MP_STATE_VM(sched_idx)];
+        mp_sched_item_t item = MP_STATE_VM(sched_queue)[MP_STATE_VM(sched_idx)];
         MP_STATE_VM(sched_idx) = IDX_MASK(MP_STATE_VM(sched_idx) + 1);
         --MP_STATE_VM(sched_len);
         MICROPY_END_ATOMIC_SECTION(atomic_state);
@@ -107,11 +107,11 @@ bool mp_sched_schedule(mp_obj_t function, mp_obj_t arg) {
             MP_STATE_VM(sched_state) = MP_SCHED_PENDING;
         }
         uint8_t iput = IDX_MASK(MP_STATE_VM(sched_idx) + MP_STATE_VM(sched_len)++);
-        MP_STATE_VM(sched_stack)[iput].func = function;
-        MP_STATE_VM(sched_stack)[iput].arg = arg;
+        MP_STATE_VM(sched_queue)[iput].func = function;
+        MP_STATE_VM(sched_queue)[iput].arg = arg;
         ret = true;
     } else {
-        // schedule stack is full
+        // schedule queue is full
         ret = false;
     }
     MICROPY_END_ATOMIC_SECTION(atomic_state);