py/scheduler: Break out of the c task loop on re-schedule.

pi-anl · pi-anl · commit af4a8e9cfc6d · 2025-05-05T16:37:58.000+10:00
Signed-off-by: Andrew Leech &lt;andrew.leech@planetinnovation.com.au&gt;
diff --git a/py/scheduler.c b/py/scheduler.c
@@ -88,11 +88,14 @@ static inline void mp_sched_run_pending(void) {
 
     #if MICROPY_SCHEDULER_STATIC_NODES
     // Run all pending C callbacks.
-    while (MP_STATE_VM(sched_head) != NULL) {
+    bool pass_finished = false;
+    while (MP_STATE_VM(sched_head) != NULL && !pass_finished) {
         mp_sched_node_t *node = MP_STATE_VM(sched_head);
         MP_STATE_VM(sched_head) = node->next;
         if (MP_STATE_VM(sched_head) == NULL) {
             MP_STATE_VM(sched_tail) = NULL;
+            // ensure we exit even if a task re-scheduled in callback() below.
+            pass_finished = true;
         }
         mp_sched_callback_t callback = node->callback;
         node->callback = NULL;
