esp32/machine_timer: Do not free interrupt from ISR.

DvdGiessen · DvdGiessen · commit f99cd078e351 · 2025-05-07T17:00:38.000+02:00
esp_intr_free is not safe to call from the timer ISR because it requires
the current task (the one the ISR interrupted) to be pinned to the same
core as the interrupt was allocated on. Merely disabling the ISR however is
safe since that only requires that we're currently running on the same core
(which the ISR always is), regardless of the current task.

This was causing deadlocks in machine_uart when the ISR happened to
interrupt a task that was not pinned to a specific core.

Signed-off-by: Daniël van de Giessen &lt;daniel@dvdgiessen.nl&gt;
diff --git a/ports/esp32/machine_timer.c b/ports/esp32/machine_timer.c
@@ -50,12 +50,13 @@
 const mp_obj_type_t machine_timer_type;
 
 static mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args);
+static mp_obj_t machine_timer_deinit(mp_obj_t self_in);
 
 void machine_timer_deinit_all(void) {
     // Disable, deallocate and remove all timers from list
     machine_timer_obj_t **t = &MP_STATE_PORT(machine_timer_obj_head);
     while (*t != NULL) {
-        machine_timer_disable(*t);
+        machine_timer_deinit(*t);
         machine_timer_obj_t *next = (*t)->next;
         m_del_obj(machine_timer_obj_t, *t);
         *t = next;
@@ -96,6 +97,7 @@ machine_timer_obj_t *machine_timer_create(mp_uint_t timer) {
         self = mp_obj_malloc(machine_timer_obj_t, &machine_timer_type);
         self->group = group;
         self->index = index;
+        self->handle = NULL;
 
         // Add the timer to the linked-list of timers
         self->next = MP_STATE_PORT(machine_timer_obj_head);
@@ -131,9 +133,8 @@ void machine_timer_disable(machine_timer_obj_t *self) {
     }
 
     if (self->handle) {
-        // Free the interrupt handler.
-        esp_intr_free(self->handle);
-        self->handle = NULL;
+        // Disable the interrupt
+        ESP_ERROR_CHECK(esp_intr_disable(self->handle));
     }
 
     // We let the disabled timer stay in the list, as it might be
@@ -167,6 +168,10 @@ void machine_timer_enable(machine_timer_obj_t *self, void (*timer_isr)) {
     // Allocate and enable the alarm interrupt.
     timer_ll_enable_intr(self->hal_context.dev, TIMER_LL_EVENT_ALARM(self->index), false);
     timer_ll_clear_intr_status(self->hal_context.dev, TIMER_LL_EVENT_ALARM(self->index));
+    if (self->handle) {
+        ESP_ERROR_CHECK(esp_intr_free(self->handle));
+        self->handle = NULL;
+    }
     ESP_ERROR_CHECK(
         esp_intr_alloc(timer_group_periph_signals.groups[self->group].timer_irq_id[self->index],
             TIMER_FLAGS, timer_isr, self, &self->handle)
@@ -233,7 +238,13 @@ static mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, mp_uint_t n
 }
 
 static mp_obj_t machine_timer_deinit(mp_obj_t self_in) {
-    machine_timer_disable(self_in);
+    machine_timer_obj_t *self = self_in;
+
+    machine_timer_disable(self);
+    if (self->handle) {
+        ESP_ERROR_CHECK(esp_intr_free(self->handle));
+        self->handle = NULL;
+    }
 
     return mp_const_none;
 }
