7123972: test/java/lang/annotation/loaderLeak/Main.java fails intermittently

Reviewed-by: dholmes, smarks
Contributed-by: NEric Wang <yiming.wang@oracle.com>

test/ProblemList.txt

@@ -122,9 +122,6 @@
 
 # jdk_lang
 
-# 7123972
-java/lang/annotation/loaderLeak/Main.java			generic-all
-
 # 6944188
 java/lang/management/ThreadMXBean/ThreadStateTest.java          generic-all
 

test/java/lang/annotation/loaderLeak/Main.java

@@ -57,9 +57,17 @@ public class Main {
         System.gc();
         System.gc();
         loader = null;
+
+        // Might require multiple calls to System.gc() for weak-references
+        // processing to be complete. If the weak-reference is not cleared as
+        // expected we will hang here until timed out by the test harness.
+        while (true) {
             System.gc();
-        System.gc();
-        if (c.get() != null) throw new AssertionError();
+            Thread.sleep(20);
+            if (c.get() == null) {
+                break;
+            }
+        }
     }
 }