Enqueue reference (slow)

Author: qinsoon

openjdk/mmtkUpcalls.cpp

@@ -321,6 +321,11 @@ static void mmtk_prepare_for_roots_re_scanning() {
 
 static void mmtk_enqueue_reference(void* object) {
   printf("enqueue object: %p\n", object);
+  MutexLocker x(Heap_lock);
+  oop reff = (oop) object;
+  oop old = Universe::swap_reference_pending_list(reff);
+  HeapAccess<AS_NO_KEEPALIVE>::oop_store_at(reff, java_lang_ref_Reference::discovered_offset, old);
+  assert(Universe::has_reference_pending_list(), "Reference pending list is empty after swap");
 }
 
 OpenJDK_Upcalls mmtk_upcalls = {

openjdk/mmtkVMCompanionThread.cpp

@@ -75,6 +75,12 @@ void MMTkVMCompanionThread::run() {
       _reached_state = _threads_resumed;
       _lock->notify_all();
     }
+    {
+      MutexLocker x(Heap_lock);
+      if (Universe::has_reference_pending_list()) {
+        Heap_lock->notify_all();
+      }
+    }
   }
 }