esp32/machine_wdt: Allow feeding WDT from threads.

This changes the ESP32 WDT implementation to use a custom handle so that it
becomes possible to reset the WDT from a thread.

By default esp_task_wdt_add subscribes the task_id of the current task.
That means that if we're running in a different task we are unable to reset
the WDT, which prevents feeding the WDT from a thread directly, or even
from a timer (which may randomly run in a different task when there's
multiple threads).

As an added bonus, the name we set makes the error clearly specify that it
was the user-specified WDT that reset the chip.

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

ports/esp32/machine_wdt.c

@@ -37,9 +37,12 @@ const mp_obj_type_t machine_wdt_type;
 
 typedef struct _machine_wdt_obj_t {
     mp_obj_base_t base;
+    esp_task_wdt_user_handle_t twdt_user_handle;
 } machine_wdt_obj_t;
 
-STATIC machine_wdt_obj_t wdt_default = {{&machine_wdt_type}};
+STATIC machine_wdt_obj_t wdt_default = {
+    {&machine_wdt_type}, 0
+};
 
 STATIC mp_obj_t machine_wdt_make_new(const mp_obj_type_t *type_in, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
     enum { ARG_id, ARG_timeout };
@@ -68,14 +71,22 @@ STATIC mp_obj_t machine_wdt_make_new(const mp_obj_type_t *type_in, size_t n_args
         mp_raise_OSError(rs_code);
     }
 
-    esp_task_wdt_add(NULL);
+    if (wdt_default.twdt_user_handle == NULL) {
+        rs_code = esp_task_wdt_add_user("mpy_machine_wdt", &wdt_default.twdt_user_handle);
+        if (rs_code != ESP_OK) {
+            mp_raise_OSError(rs_code);
+        }
+    }
 
     return &wdt_default;
 }
 
 STATIC mp_obj_t machine_wdt_feed(mp_obj_t self_in) {
     (void)self_in;
-    esp_task_wdt_reset();
+    mp_int_t rs_code = esp_task_wdt_reset_user(wdt_default.twdt_user_handle);
+    if (rs_code != ESP_OK) {
+        mp_raise_OSError(rs_code);
+    }
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_wdt_feed_obj, machine_wdt_feed);