shared/runtime/softtimer: Add support for hard callbacks.

arachsys · arachsys · commit 06229b58f317 · 2025-06-29T11:29:47.000+01:00
Add a flag SOFT_TIMER_HARD_CALLBACK to request that a soft timer's python
callback is run directly from the IRQ handler with the scheduler and heap
locked, instead of being scheduled via mp_sched_schedule().

Signed-off-by: Chris Webb &lt;chris@arachsys.com&gt;
diff --git a/shared/runtime/softtimer.c b/shared/runtime/softtimer.c
@@ -88,7 +88,27 @@ void soft_timer_handler(void) {
         soft_timer_entry_t *entry = heap;
         heap = (soft_timer_entry_t *)mp_pairheap_pop(soft_timer_lt, &heap->pairheap);
         if (entry->flags & SOFT_TIMER_FLAG_PY_CALLBACK) {
-            mp_sched_schedule(entry->py_callback, MP_OBJ_FROM_PTR(entry));
+            if (entry->flags & SOFT_TIMER_FLAG_HARD_CALLBACK) {
+                // When executing code within a handler we must lock the scheduler to
+                // prevent any scheduled callbacks from running, and lock the GC to
+                // prevent any memory allocations.
+                mp_sched_lock();
+                gc_lock();
+                nlr_buf_t nlr;
+                if (nlr_push(&nlr) == 0) {
+                    mp_call_function_1(entry->py_callback, MP_OBJ_FROM_PTR(entry));
+                    nlr_pop();
+                } else {
+                    // Uncaught exception; disable the callback so it doesn't run again.
+                    entry->mode = SOFT_TIMER_MODE_ONE_SHOT;
+                    mp_printf(MICROPY_ERROR_PRINTER, "uncaught exception in timer callback\n");
+                    mp_obj_print_exception(MICROPY_ERROR_PRINTER, MP_OBJ_FROM_PTR(nlr.ret_val));
+                }
+                gc_unlock();
+                mp_sched_unlock();
+            } else {
+                mp_sched_schedule(entry->py_callback, MP_OBJ_FROM_PTR(entry));
+            }
         } else if (entry->c_callback) {
             entry->c_callback(entry);
         }
diff --git a/shared/runtime/softtimer.h b/shared/runtime/softtimer.h
@@ -30,6 +30,7 @@
 
 #define SOFT_TIMER_FLAG_PY_CALLBACK (1)
 #define SOFT_TIMER_FLAG_GC_ALLOCATED (2)
+#define SOFT_TIMER_FLAG_HARD_CALLBACK (4)
 
 #define SOFT_TIMER_MODE_ONE_SHOT (1)
 #define SOFT_TIMER_MODE_PERIODIC (2)
