Change ReferenceQueue.add to append at end of the unenqueued list

We now append the singly linked list at the end of the queue.
Previously the list was added after the first element of the
unenqueued list.

Bug: 17381967

(cherry picked from commit 37477444ae4d6fae52258f9ea85d32d5a87ebef2)

Change-Id: Ie6680df476518236037254546380a8255ad801ac

1 files changed, 12 insertions, 3 deletions

diff --git a/luni/src/main/java/java/lang/ref/ReferenceQueue.java b/luni/src/main/java/java/lang/ref/ReferenceQueue.java
index 7ddd97d..4c78fbf 100644
--- a/luni/src/main/java/java/lang/ref/ReferenceQueue.java
+++ b/luni/src/main/java/java/lang/ref/ReferenceQueue.java
@@ -153,9 +153,18 @@ public class ReferenceQueue<T> {
             if (unenqueued == null) {
                 unenqueued = list;
             } else {
-                Reference<?> next = unenqueued.pendingNext;
-                unenqueued.pendingNext = list.pendingNext;
-                list.pendingNext = next;
+                // Find the last element in unenqueued.
+                Reference<?> last = unenqueued;
+                while (last.pendingNext != unenqueued) {
+                  last = last.pendingNext;
+                }
+                // Add our list to the end. Update the pendingNext to point back to enqueued.
+                last.pendingNext = list;
+                last = list;
+                while (last.pendingNext != list) {
+                    last = last.pendingNext;
+                }
+                last.pendingNext = unenqueued;
             }
             ReferenceQueue.class.notifyAll();
         }