*** old/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.runtime/src/jdk/vm/ci/runtime/JVMCI.java	Thu Mar 28 11:24:27 2019
--- new/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.runtime/src/jdk/vm/ci/runtime/JVMCI.java	Thu Mar 28 11:24:27 2019

*** 1,7 ****
--- 1,7 ----
  /*
!  * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.

*** 22,63 ****
--- 22,80 ----
   */
  package jdk.vm.ci.runtime;
  
  import java.util.Formatter;
  
+ import jdk.vm.ci.common.NativeImageReinitialize;
+ import jdk.vm.ci.services.Services;
+ 
  public class JVMCI {
  
      private static final JVMCIRuntime runtime;
+     /**
+      * Singleton instance lazily initialized via double-checked locking.
+      */
+     @NativeImageReinitialize private static volatile JVMCIRuntime runtime;
  
!     private static native JVMCIRuntime initializeRuntime();
!     @NativeImageReinitialize private static boolean initializing;
  
      public static void initialize() {
          // force static initializer
      }
  
+     private static native JVMCIRuntime initializeRuntime();
+ 
      /**
       * Gets the singleton {@link JVMCIRuntime} instance available to the application.
       *
       * @throws UnsupportedOperationException if JVMCI is not supported
       */
      public static JVMCIRuntime getRuntime() {
          if (runtime == null) {
              String javaHome = System.getProperty("java.home");
              String vmName = System.getProperty("java.vm.name");
+         JVMCIRuntime result = runtime;
+         if (result == null) {
+             synchronized (JVMCI.class) {
+                 result = runtime;
+                 if (result == null) {
+                     if (initializing) {
+                         // In recursive call from HotSpotJVMCIRuntime.runtime
+                         // so no need to re-enter initializeRuntime below. This
+                         // path is only entered if JVMCI initialization starts
+                         // with JVMCI.getRuntime().
+                         return null;
+                     }
+                     initializing = true;
+                     try {
+                         runtime = result = initializeRuntime();
+                     } catch (UnsatisfiedLinkError e) {
+                         String javaHome = Services.getSavedProperty("java.home");
+                         String vmName = Services.getSavedProperty("java.vm.name");
                          Formatter errorMessage = new Formatter();
                          errorMessage.format("The VM does not support the JVMCI API.%n");
                          errorMessage.format("Currently used Java home directory is %s.%n", javaHome);
                          errorMessage.format("Currently used VM configuration is: %s", vmName);
                          throw new UnsupportedOperationException(errorMessage.toString());
                      }
          return runtime;
                  }
  
      static {
          JVMCIRuntime rt = null;
          try {
              rt = initializeRuntime();
          } catch (UnsatisfiedLinkError e) {
              }
          runtime = rt;
+         }
+         return result;
      }
  }