esp32/modesp32: Implement esp32.idf_task_info().

This adds a new function, `esp32.idf_task_info()`, that can be used to
retrieve task statistics which is useful for diagnosing issues where some
tasks are using up a lot of CPU time.

It's best used in conjunction with the `utop` module from micropython-lib.

Signed-off-by: Daniël van de Giessen <daniel@dvdgiessen.nl>

docs/library/esp32.rst

@@ -80,6 +80,29 @@ Functions
        The result of :func:`gc.mem_free()` is the total of the current "free"
        and "max new split" values printed by :func:`micropython.mem_info()`.
 
+.. function:: idf_task_info()
+
+    Returns information about running ESP-IDF/FreeRTOS tasks, which include
+    MicroPython threads. This data is useful to gain insight into how much time
+    tasks spend running or if they are blocked for significant parts of time,
+    and to determine if allocated stacks are fully utilized or might be reduced.
+
+    ``CONFIG_FREERTOS_USE_TRACE_FACILITY=y`` must be set in the board
+    configuration to make this method available. Additionally configuring
+    ``CONFIG_FREERTOS_GENERATE_RUN_TIME_STATS=y`` and
+    ``CONFIG_FREERTOS_VTASKLIST_INCLUDE_COREID=y`` is recommended to be able to
+    retrieve the total and per-task runtime and the core ID respectively.
+
+    The return value is a 2-tuple where the first value is the total runtime,
+    and the second a list of tasks. Each task is a 7-tuple containing: the task
+    ID, name, current state, priority, runtime, stack high water mark, and the
+    ID of the core it is running on. Runtime and core ID will be None when the
+    respective FreeRTOS configuration option is not enabled.
+
+    .. note:: For an easier to use output based on this function you can use the
+       `utop library <https://github.com/micropython/micropython-lib/tree/master/micropython/utop>`_,
+       which implements a live overview similar to the Unix ``top`` command.
+
 
 Flash partitions
 ----------------

ports/esp32/modesp32.c

@@ -212,6 +212,49 @@ static mp_obj_t esp32_idf_heap_info(const mp_obj_t cap_in) {
 }
 static MP_DEFINE_CONST_FUN_OBJ_1(esp32_idf_heap_info_obj, esp32_idf_heap_info);
 
+#if CONFIG_FREERTOS_USE_TRACE_FACILITY
+static mp_obj_t esp32_idf_task_info(void) {
+    const size_t task_count_max = uxTaskGetNumberOfTasks();
+    TaskStatus_t *task_array = m_new(TaskStatus_t, task_count_max);
+    uint32_t total_time;
+    const size_t task_count = uxTaskGetSystemState(task_array, task_count_max, &total_time);
+
+    mp_obj_list_t *task_list = MP_OBJ_TO_PTR(mp_obj_new_list(task_count, NULL));
+    for (size_t i = 0; i < task_count; i++) {
+        mp_obj_t task_data[] = {
+            mp_obj_new_int_from_uint((mp_uint_t)task_array[i].xHandle),
+            mp_obj_new_str(task_array[i].pcTaskName, strlen(task_array[i].pcTaskName)),
+            MP_OBJ_NEW_SMALL_INT(task_array[i].eCurrentState),
+            MP_OBJ_NEW_SMALL_INT(task_array[i].uxCurrentPriority),
+            #if CONFIG_FREERTOS_GENERATE_RUN_TIME_STATS
+            mp_obj_new_int_from_uint(task_array[i].ulRunTimeCounter),
+            #else
+            mp_const_none,
+            #endif
+            mp_obj_new_int_from_uint(task_array[i].usStackHighWaterMark),
+            #if CONFIG_FREERTOS_VTASKLIST_INCLUDE_COREID
+            MP_OBJ_NEW_SMALL_INT(task_array[i].xCoreID),
+            #else
+            mp_const_none,
+            #endif
+        };
+        task_list->items[i] = mp_obj_new_tuple(7, task_data);
+    }
+
+    m_del(TaskStatus_t, task_array, task_count_max);
+    mp_obj_t task_stats[] = {
+        #if CONFIG_FREERTOS_GENERATE_RUN_TIME_STATS
+        MP_OBJ_NEW_SMALL_INT(total_time),
+        #else
+        mp_const_none,
+        #endif
+        task_list
+    };
+    return mp_obj_new_tuple(2, task_stats);
+}
+static MP_DEFINE_CONST_FUN_OBJ_0(esp32_idf_task_info_obj, esp32_idf_task_info);
+#endif
+
 static const mp_rom_map_elem_t esp32_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_esp32) },
 
@@ -228,6 +271,9 @@ static const mp_rom_map_elem_t esp32_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_mcu_temperature), MP_ROM_PTR(&esp32_mcu_temperature_obj) },
     #endif
     { MP_ROM_QSTR(MP_QSTR_idf_heap_info), MP_ROM_PTR(&esp32_idf_heap_info_obj) },
+    #if CONFIG_FREERTOS_USE_TRACE_FACILITY
+    { MP_ROM_QSTR(MP_QSTR_idf_task_info), MP_ROM_PTR(&esp32_idf_task_info_obj) },
+    #endif
 
     { MP_ROM_QSTR(MP_QSTR_NVS), MP_ROM_PTR(&esp32_nvs_type) },
     { MP_ROM_QSTR(MP_QSTR_Partition), MP_ROM_PTR(&esp32_partition_type) },