From 58623faf53138f63ec1a8a73612fb55d68e9e25a Mon Sep 17 00:00:00 2001
From: Doug Lea <dl@openjdk.org>
Date: Mon, 28 Nov 2016 23:39:54 -0800
Subject: [PATCH] 8166507: ConcurrentSkipListSet.clear() can leave the Set in
 an invalid state

Reviewed-by: martin, smarks, psandoz
---
 .../concurrent/ConcurrentSkipListMap.java     | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentSkipListMap.java b/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentSkipListMap.java
index 7734a265bed..2ae29aa42f3 100644
--- a/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentSkipListMap.java
+++ b/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentSkipListMap.java
@@ -1650,7 +1650,24 @@ public class ConcurrentSkipListMap<K,V> extends AbstractMap<K,V>
      * Removes all of the mappings from this map.
      */
     public void clear() {
-        initialize();
+        for (;;) {
+            Node<K,V> b, n;
+            HeadIndex<K,V> h = head, d = (HeadIndex<K,V>)h.down;
+            if (d != null)
+                casHead(h, d);            // remove levels
+            else if ((b = h.node) != null && (n = b.next) != null) {
+                Node<K,V> f = n.next;     // remove values
+                if (n == b.next) {
+                    Object v = n.value;
+                    if (v == null)
+                        n.helpDelete(b, f);
+                    else if (n.casValue(v, null) && n.appendMarker(f))
+                        b.casNext(n, f);
+                }
+            }
+            else
+                break;
+        }
     }
 
     /**