[FIXED JENKINS-15796] NoClassDefFoundError: 'Could not initialize class...

[FIXED JENKINS-15796] NoClassDefFoundError: 'Could not initialize class org.jvnet.hudson.Windows$MEMORYSTATUSEX' from SwapSpaceMonitor.
Not fixing actual linkage error—JNA issue of some kind—but ensuring that Jenkins reports it only once.

changelog.html

@@ -64,6 +64,9 @@ Upcoming changes</a>
   <li class=bug>
     Preview function for textareas using Jenkins markup did not work when CSRF protection was enabled.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-17085">issue 17085</a>)
+  <li class=bug>
+    JNA-related error from Windows slave monitoring thrown repeatedly.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-15796">issue 15796</a>)
   <li class=rfe>
     Improved the request handling performance (where the file lookup is expensive, such as NFS.)
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-16606">issue 16606</a>)

core/src/main/java/hudson/node_monitors/SwapSpaceMonitor.java

@@ -102,17 +102,22 @@ public class SwapSpaceMonitor extends NodeMonitor {
             try {
                 mm = MemoryMonitor.get();
             } catch (IOException e) {
-                if(!warned) {
-                    // report the problem just once, and avoid filling up the log with the same error. see HUDSON-2194.
-                    warned = true;
-                    throw e;
-                } else {
-                    return null;
-                }
+                return report(e);
+            } catch (LinkageError e) { // JENKINS-15796
+                return report(e);
             }
             return new MemoryUsage2(mm.monitor());
         }
 
+        private <T extends Throwable> MemoryUsage report(T e) throws T {
+            if (!warned) {
+                warned = true;
+                throw e;
+            } else { // JENKINS-2194
+                return null;
+            }
+        }
+
         private static final long serialVersionUID = 1L;
 
         private static boolean warned = false;