[FIXED JENKINS-24358] RunSaveableReference.get can acquire locks, so avoid...

[FIXED JENKINS-24358] RunSaveableReference.get can acquire locks, so avoid calling it while holding a lock on ourselves.

changelog.html

@@ -58,6 +58,9 @@ Upcoming changes</a>
   <li class=rfe>
     Added 'no-store' to the 'Cache-Control' header to avoid accidental information leak through local cache backup
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-24337">issue 24337</a>)
+  <li class=bug>
+    Deadlock in <code>OldDataMonitor</code>.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-24358">issue 24358</a>)
 </ul>
 </div><!--=TRUNK-END=-->
 

core/src/main/java/hudson/diagnosis/OldDataMonitor.java

@@ -84,9 +84,13 @@ public class OldDataMonitor extends AdministrativeMonitor {
         return !data.isEmpty();
     }
 
-    public synchronized Map<Saveable,VersionRange> getData() {
+    public Map<Saveable,VersionRange> getData() {
+        Map<SaveableReference,VersionRange> _data;
+        synchronized (this) {
+            _data = new HashMap<SaveableReference,VersionRange>(this.data);
+        }
         Map<Saveable,VersionRange> r = new HashMap<Saveable,VersionRange>();
-        for (Map.Entry<SaveableReference,VersionRange> entry : data.entrySet()) {
+        for (Map.Entry<SaveableReference,VersionRange> entry : _data.entrySet()) {
             Saveable s = entry.getKey().get();
             if (s != null) {
                 r.put(s, entry.getValue());