8256106: Bypass intrinsic/barrier when calling Reference.get() from Finalizer

Reviewed-by: eosterlund

Author: rkennke

src/java.base/share/classes/java/lang/ref/Finalizer.java

@@ -82,7 +82,7 @@ private void runFinalizer(JavaLangAccess jla) {
         }
 
         try {
-            Object finalizee = this.get();
+            Object finalizee = this.getInactive();
             if (finalizee != null && !(finalizee instanceof java.lang.Enum)) {
                 jla.invokeFinalize(finalizee);
 

src/java.base/share/classes/java/lang/ref/Reference.java

@@ -342,6 +342,20 @@ public T get() {
         return this.referent;
     }
 
+    /**
+     * Load referent with strong semantics. Treating the referent
+     * as strong referent is ok when the Reference is inactive,
+     * because then the referent is switched to strong semantics
+     * anyway.
+     *
+     * This is only used from Finalizer to bypass the intrinsic,
+     * which might return a null referent, even though it is not
+     * null, and would subsequently not finalize the referent/finalizee.
+     */
+    T getInactive() {
+        return this.referent;
+    }
+
     /**
      * Tests if the referent of this reference object is {@code obj}.
      * Using a {@code null} {@code obj} returns {@code true} if the