Merge pull request #4122 from hathach/fix-3986

Fix 3986 background reset remove existing usb callback

main.c

@@ -184,6 +184,7 @@ STATIC void stop_mp(void) {
     #endif
 
     background_callback_reset();
+    usb_background();
 
     gc_deinit();
 }

ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk

@@ -11,3 +11,4 @@ LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
 
 SUPEROPT_GC = 0
+SUPEROPT_VM = 0

ports/atmel-samd/boards/seeeduino_xiao/mpconfigboard.mk

@@ -11,3 +11,4 @@ LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
 
 SUPEROPT_GC = 0
+SUPEROPT_VM = 0

supervisor/shared/background_callback.c

@@ -33,7 +33,7 @@
 #include "supervisor/shared/tick.h"
 #include "shared-bindings/microcontroller/__init__.h"
 
-STATIC volatile background_callback_t *callback_head, *callback_tail;
+STATIC volatile background_callback_t * volatile callback_head, * volatile callback_tail;
 
 #define CALLBACK_CRITICAL_BEGIN (common_hal_mcu_disable_interrupts())
 #define CALLBACK_CRITICAL_END (common_hal_mcu_enable_interrupts())
@@ -50,7 +50,6 @@ void background_callback_add_core(background_callback_t *cb) {
     cb->prev = (background_callback_t*)callback_tail;
     if (callback_tail) {
         callback_tail->next = cb;
-        cb->prev = (background_callback_t*)callback_tail;
     }
     if (!callback_head) {
         callback_head = cb;

supervisor/shared/usb/usb.c

@@ -111,9 +111,14 @@ static void usb_background_do(void* unused) {
     usb_background();
 }
 
+void usb_background_schedule(void)
+{
+    background_callback_add(&usb_callback, usb_background_do, NULL);
+}
+
 void usb_irq_handler(void) {
     tud_int_handler(0);
-    background_callback_add(&usb_callback, usb_background_do, NULL);
+    usb_background_schedule();
 }
 
 //--------------------------------------------------------------------+

supervisor/usb.h

@@ -35,6 +35,9 @@
 // it may be necessary to call it directly.
 void usb_background(void);
 
+// Schedule usb background
+void usb_background_schedule(void);
+
 // Ports must call this from their particular USB IRQ handler
 void usb_irq_handler(void);