[FIXED JENKINS-21437] Mismatched synchronization monitor.

changelog.html

@@ -55,7 +55,9 @@ Upcoming changes</a>
 <!-- Record your changes in the trunk here. -->
 <div id="trunk" style="display:none"><!--=TRUNK-BEGIN=-->
 <ul class=image>
-  <li class=>
+  <li class=bug>
+    <code>ConcurrentModificationException</code> in <code>RunListProgressiveRendering</code>.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-21437">issue 21437</a>)
 </ul>
 </div><!--=TRUNK-END=-->
 

core/src/main/java/jenkins/widgets/RunListProgressiveRendering.java

@@ -63,7 +63,7 @@ public abstract class RunListProgressiveRendering extends ProgressiveRendering {
             }
             JSONObject element = new JSONObject();
             calculate(build, element);
-            synchronized (results) {
+            synchronized (this) {
                 results.add(element);
             }
             decay *= (1 - 1 / MAX_LIKELY_RUNS);