--- a/client/swing/src/main/java/com/redhat/thermostat/client/swing/internal/vmlist/controller/HostTreeController.java	Thu Sep 22 09:25:33 2016 -0400
+++ b/client/swing/src/main/java/com/redhat/thermostat/client/swing/internal/vmlist/controller/HostTreeController.java	Fri Sep 23 10:04:43 2016 -0400
@@ -237,7 +237,12 @@
     }
 
     public synchronized void registerVM(final VmRef vm) {
-        addVMImpl(vm);
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                addVMImpl(vm);
+            }
+        });
     }
 
     private AccordionComponent getHostComponent(HostRef reference) {
@@ -394,18 +399,28 @@
         return decoratorManager;
     }
 
-    public void addFilter(ReferenceFilter filter) {
-        filterMap.clear();
-        filters.add(filter);
-        filter.addFilterEventListener(filterListener);
-        rebuildTree();
+    public void addFilter(final ReferenceFilter filter) {
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                filterMap.clear();
+                filters.add(filter);
+                filter.addFilterEventListener(filterListener);
+                rebuildTree();
+            }
+        });
     }
 
-    public void removeFilter(ReferenceFilter filter) {
-        filterMap.clear();
-        filters.remove(filter);
-        filter.removeFilterEventListener(filterListener);
-        rebuildTree();
+    public void removeFilter(final ReferenceFilter filter) {
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                filterMap.clear();
+                filters.remove(filter);
+                filter.removeFilterEventListener(filterListener);
+                rebuildTree();
+            }
+        });
     }
 
     public void expandNode(final HostRef reference) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/client/swing/src/test/java/com/redhat/thermostat/client/swing/internal/vmlist/controller/HostTreeControllerCacioTest.java	Fri Sep 23 10:04:43 2016 -0400
@@ -0,0 +1,197 @@
+/*
+ * Copyright 2012-2016 Red Hat, Inc.
+ *
+ * This file is part of Thermostat.
+ *
+ * Thermostat is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2, or (at your
+ * option) any later version.
+ *
+ * Thermostat is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Thermostat; see the file COPYING.  If not see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Linking this code with other modules is making a combined work
+ * based on this code.  Thus, the terms and conditions of the GNU
+ * General Public License cover the whole combination.
+ *
+ * As a special exception, the copyright holders of this code give
+ * you permission to link this code with independent modules to
+ * produce an executable, regardless of the license terms of these
+ * independent modules, and to copy and distribute the resulting
+ * executable under terms of your choice, provided that you also
+ * meet, for each linked independent module, the terms and conditions
+ * of the license of that module.  An independent module is a module
+ * which is not derived from or based on this code.  If you modify
+ * this code, you may extend this exception to your version of the
+ * library, but you are not obligated to do so.  If you do not wish
+ * to do so, delete this exception statement from your version.
+ */
+
+package com.redhat.thermostat.client.swing.internal.vmlist.controller;
+
+import com.redhat.thermostat.annotations.internal.CacioTest;
+import com.redhat.thermostat.client.swing.internal.accordion.Accordion;
+import com.redhat.thermostat.client.swing.internal.vmlist.HostTreeComponentFactory;
+import com.redhat.thermostat.client.ui.ReferenceFilter;
+import com.redhat.thermostat.common.internal.test.Bug;
+import com.redhat.thermostat.storage.core.HostRef;
+import com.redhat.thermostat.storage.core.Ref;
+import com.redhat.thermostat.storage.core.VmRef;
+import net.java.openjdk.cacio.ctc.junit.CacioFESTRunner;
+import org.fest.swing.annotation.GUITest;
+import org.fest.swing.edt.FailOnThreadViolationRepaintManager;
+import org.fest.swing.edt.GuiActionRunner;
+import org.fest.swing.edt.GuiTask;
+import org.fest.swing.fixture.FrameFixture;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.junit.runner.RunWith;
+
+import javax.swing.JFrame;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.Assert.fail;
+
+@Category(CacioTest.class)
+@RunWith(CacioFESTRunner.class)
+public class HostTreeControllerCacioTest {
+
+    private Accordion<HostRef, VmRef> accordion;
+    private DecoratorManager decoratorManager;
+    private HostTreeComponentFactory componentFactory;
+    private HostTreeController controller;
+
+    private FrameFixture frameFixture;
+    private JFrame window;
+
+    @BeforeClass
+    public static void beforeClass() {
+        FailOnThreadViolationRepaintManager.install();
+    }
+
+    @Before
+    public void setup() {
+        GuiActionRunner.execute(new GuiTask() {
+            @Override
+            protected void executeInEDT() throws Throwable {
+                window = new JFrame();
+
+                decoratorManager = new DecoratorManager();
+                componentFactory = new HostTreeComponentFactory(decoratorManager, new ContextActionController());
+                accordion = new Accordion<>(componentFactory);
+
+                window.add(accordion);
+                window.pack();
+
+                controller = new HostTreeController(accordion, decoratorManager, componentFactory);
+            }
+        });
+
+        frameFixture = new FrameFixture(window);
+    }
+
+    @After
+    public void cleanup() {
+        frameFixture.cleanUp();
+    }
+
+    @Bug(id = "PR3148",
+            url = "http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=3148",
+            summary = "NPE in Accordion when rapid concurrent host/vm registration and filter additions interleave")
+    @Category(GUITest.class)
+    @Test
+    public void testThreadedAddFilters() throws InterruptedException, IOException {
+        PrintStream origOut = System.out;
+        PrintStream origErr = System.err;
+
+        try (ByteArrayOutputStream outStream = new ByteArrayOutputStream();
+             ByteArrayOutputStream errStream = new ByteArrayOutputStream()) {
+
+            System.setOut(new PrintStream(outStream));
+            System.setErr(new PrintStream(errStream));
+
+            // manual testing showed a ~20% hit rate for this bug, so 50 iterations should be
+            // far more than enough to catch it at least once
+            for (int i = 0; i < 50; i++) {
+                performThreadedAccordionTest();
+            }
+
+            String outContents = outStream.toString();
+            String errContents = errStream.toString();
+
+            assertNoExceptions(outContents);
+            assertNoExceptions(errContents);
+
+            outStream.reset();
+            errStream.reset();
+        } finally {
+            System.setOut(origOut);
+            System.setErr(origErr);
+        }
+    }
+
+    private void performThreadedAccordionTest() throws InterruptedException {
+        final HostRef host1 = new HostRef("host1", "host1");
+        final HostRef host2 = new HostRef("host2", "host2");
+        final VmRef vm1 = new VmRef(host1, "vm1", 100, "foo-vm");
+        final VmRef vm2 = new VmRef(host2, "vm2", 200, "bar-vm");
+        final ReferenceFilter filter = new ReferenceFilter() {
+            @Override
+            public boolean matches(Ref toMatch) {
+                return true;
+            }
+        };
+
+        Thread addHostsThread = new Thread(new Runnable() {
+            @Override
+            public void run() {
+                controller.registerHost(host1);
+                controller.registerHost(host2);
+            }
+        });
+        Thread addVmsThread = new Thread(new Runnable() {
+            @Override
+            public void run() {
+                controller.registerVM(vm1);
+                controller.registerVM(vm2);
+            }
+        });
+        Thread addFiltersThread = new Thread(new Runnable() {
+            @Override
+            public void run() {
+                controller.addFilter(filter);
+            }
+        });
+
+        List<Thread> threads = Arrays.asList(addHostsThread, addVmsThread, addFiltersThread);
+        Collections.shuffle(threads);
+        for (Thread t : threads) {
+            t.start();
+        }
+        for (Thread t : threads) {
+            t.join();
+        }
+    }
+
+    private void assertNoExceptions(String str) {
+        if (str.contains("exception") || str.contains("Exception")) {
+            fail("Test failed:\n" + str);
+        }
+    }
+
+}

--- a/client/swing/src/test/java/com/redhat/thermostat/client/swing/internal/vmlist/controller/HostTreeControllerTest.java	Thu Sep 22 09:25:33 2016 -0400
+++ b/client/swing/src/test/java/com/redhat/thermostat/client/swing/internal/vmlist/controller/HostTreeControllerTest.java	Fri Sep 23 10:04:43 2016 -0400
@@ -160,8 +160,9 @@
         HostRef host1 = new HostRef("1", "1");
         
         controller.registerHost(host0);
+        waitForSwing();
+
         controller.registerHost(host1);
-        
         waitForSwing();
         
         // check if our model contains everything it's supposed to
@@ -184,6 +185,7 @@
         controller.addFilter(filter1);
         
         waitForSwing();
+        waitForSwing();
         
         // we need to check that the model is rebuild with the appropriate
         // hosts, the filter should only let one host in
@@ -197,6 +199,7 @@
         
         waitForSwing();
         waitForSwing();
+        waitForSwing();
 
         headers = proxyModel.getHeaders();
         assertEquals(2, headers.size());
@@ -214,7 +217,8 @@
         controller.addFilter(filter2);
         
         waitForSwing();
-        
+        waitForSwing();
+
         headers = proxyModel.getHeaders();
         assertEquals(2, headers.size());
         
@@ -227,7 +231,8 @@
         controller.registerVM(vm2);
         
         waitForSwing();
-        
+        waitForSwing();
+
         List<VmRef> components  = proxyModel.getComponents(host0);
         assertEquals(2, components.size());
         assertTrue(components.contains(vm0));
@@ -309,6 +314,7 @@
         controller.registerVM(vm2);
         
         waitForSwing();
+        waitForSwing();
 
         List<VmRef> components  = proxyModel.getComponents(host0);
         assertEquals(1, components.size());