Merge pull request #4122 from hathach/fix-3986

Fix 3986 background reset remove existing usb callback

3 files changed, 10 insertions, 3 deletions

diff --git a/supervisor/shared/background_callback.c b/supervisor/shared/background_callback.c
index 288c9a4df..68a0a9667 100644
--- a/supervisor/shared/background_callback.c
+++ b/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;
diff --git a/supervisor/shared/usb/usb.c b/supervisor/shared/usb/usb.c
index 06b9e0c4e..43564d5d5 100644
--- a/supervisor/shared/usb/usb.c
+++ b/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();
 }
 
 //--------------------------------------------------------------------+
diff --git a/supervisor/usb.h b/supervisor/usb.h
index ccb35470c..1c709926a 100644
--- a/supervisor/usb.h
+++ b/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);