[FIXED JENKINS-19446]

Defer the notification to avoid deadlock.

changelog.html

@@ -63,6 +63,9 @@ Upcoming changes</a>
 <div id="rc" style="display:none;"><!--=BEGIN=-->
 <h3><a name=v1.543>What's new in 1.543</a> <!--=DATE=--></h3>
 <ul class=image>
+  <li class=bug>
+    Fixed a possible dead lock problem in deleting projects.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-19446">issue 19446</a>)
   <li class=bug>
     HTML metacharacters not escaped in log messages.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-20800">issue 20800</a>)

core/src/main/java/hudson/model/AbstractItem.java

@@ -42,6 +42,7 @@ import hudson.util.AlternativeUiTextProvider.Message;
 import hudson.util.AtomicFileWriter;
 import hudson.util.IOUtils;
 import jenkins.model.Jenkins;
+import jenkins.model.Jenkins.MasterComputer;
 import org.apache.tools.ant.taskdefs.Copy;
 import org.apache.tools.ant.types.FileSet;
 import org.kohsuke.stapler.WebMethod;
@@ -510,21 +511,23 @@ public abstract class AbstractItem extends Actionable implements Item, HttpDelet
         checkPermission(DELETE);
         performDelete();
 
-        try {
-            invokeOnDeleted();
-        } catch (AbstractMethodError e) {
-            // ignore
-        }
-
-        Jenkins.getInstance().rebuildDependencyGraphAsync();
-    }
+        // defer the notification to avoid the lock ordering problem. See JENKINS-19446.
+        MasterComputer.threadPoolForRemoting.submit(new java.util.concurrent.Callable<Void>() {
+            @Override
+            public Void call() throws Exception {
+                invokeOnDeleted();
+                Jenkins.getInstance().rebuildDependencyGraphAsync();
+                return null;
+            }
 
-    /**
-     * A pointless function to work around what appears to be a HotSpot problem. See JENKINS-5756 and bug 6933067
-     * on BugParade for more details.
-     */
-    private void invokeOnDeleted() throws IOException {
-        getParent().onDeleted(this);
+            /**
+             * A pointless function to work around what appears to be a HotSpot problem. See JENKINS-5756 and bug 6933067
+             * on BugParade for more details.
+             */
+            private void invokeOnDeleted() throws IOException {
+                getParent().onDeleted(AbstractItem.this);
+            }
+        });
     }
 
     /**