6495521: (doc) ConcurrentSkipListMap links to web page NOT describing SkipList

Update link, and minor implementation comment in Exchanger

Reviewed-by: chegar, mduigou

jdk/src/share/classes/java/util/concurrent/ConcurrentSkipListMap.java

@@ -44,8 +44,8 @@ import java.util.concurrent.atomic.*;
  * creation time, depending on which constructor is used.
  *
  * <p>This class implements a concurrent variant of <a
- * href="http://www.cs.umd.edu/~pugh/">SkipLists</a> providing
- * expected average <i>log(n)</i> time cost for the
+ * href="http://en.wikipedia.org/wiki/Skip_list" target="_top">SkipLists</a>
+ * providing expected average <i>log(n)</i> time cost for the
  * <tt>containsKey</tt>, <tt>get</tt>, <tt>put</tt> and
  * <tt>remove</tt> operations and their variants.  Insertion, removal,
  * update, and access operations safely execute concurrently by

jdk/src/share/classes/java/util/concurrent/Exchanger.java

@@ -164,8 +164,8 @@ public class Exchanger<V> {
      * races between two threads or thread pre-emptions occurring
      * between reading and CASing.  Also, very transient peak
      * contention can be much higher than the average sustainable
-     * levels.  The max limit is decreased on average 50% of the times
-     * that a non-slot-zero wait elapses without being fulfilled.
+     * levels.  An attempt to decrease the max limit is usually made
+     * when a non-slot-zero wait elapses without being fulfilled.
      * Threads experiencing elapsed waits move closer to zero, so
      * eventually find existing (or future) threads even if the table
      * has been shrunk due to inactivity.  The chosen mechanics and