rp2/mpthreadport: Fix memory corruption when thread is created in core1.

The stack (and arg) of core1 is itself a root pointer, not just the entries
in it.  Without this fix the GC could reclaim the entire stack (and
argument object).

Fixes issues #7124 and #7981.

1 files changed, 6 insertions, 6 deletions

diff --git a/ports/rp2/mpthreadport.c b/ports/rp2/mpthreadport.c
index 8a36cfca7..cdb5945d2 100644
--- a/ports/rp2/mpthreadport.c
+++ b/ports/rp2/mpthreadport.c
@@ -52,12 +52,12 @@ void mp_thread_deinit(void) {
 }
 
 void mp_thread_gc_others(void) {
-    if (get_core_num() == 0) {
-        // GC running on core0, trace core1's stack, if it's running.
-        if (core1_entry != NULL) {
-            gc_collect_root((void **)core1_stack, core1_stack_num_words);
-        }
-    } else {
+    if (core1_entry != NULL) {
+        // Collect core1's stack if it is active.
+        gc_collect_root((void **)&core1_stack, 1);
+        gc_collect_root((void **)&core1_arg, 1);
+    }
+    if (get_core_num() == 1) {
         // GC running on core1, trace core0's stack.
         gc_collect_root((void **)&__StackBottom, (&__StackTop - &__StackBottom) / sizeof(uintptr_t));
     }