Enables clean VM shutdown.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 7bb4fe3a399569edb61915240c5af47eb247d4d3..519c469f3db3405549099a64d73505cc3e7f170e 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -14,6 +14,7 @@
 #include "vm/handles.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
+#include "vm/message.h"
 #include "vm/metrics.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
@@ -198,18 +199,21 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
 
 
 const char* Dart::Cleanup() {
-  // Shutdown the service isolate before shutting down the thread pool.
-  ServiceIsolate::Shutdown();
-#if 0
-  // Ideally we should shutdown the VM isolate here, but the thread pool
-  // shutdown does not seem to ensure that all the threads have stopped
-  // execution before it terminates, this results in racing isolates.
+  ASSERT(Isolate::Current() == NULL);
   if (vm_isolate_ == NULL) {
     return "VM already terminated.";
   }
 
-  ASSERT(Isolate::Current() == NULL);
+  // Disable the creation of new isolates.
+  Isolate::DisableIsolateCreation();
+
+  // Send the OOB Kill message to all remaining isolates.
+  Isolate::KillAllIsolates();
+
+  // Shutdown the service isolate before shutting down the thread pool.
+  ServiceIsolate::Shutdown();
 
+  // Shutdown the thread pool. On return, all thread pool threads have exited.
   delete thread_pool_;
   thread_pool_ = NULL;
 
@@ -217,19 +221,14 @@ const char* Dart::Cleanup() {
   Thread::EnsureInit();
   Thread::EnterIsolate(vm_isolate_);
 
-  // There is a planned and known asymmetry here: We exit one scope for the VM
-  // isolate to account for the scope that was entered in Dart_InitOnce.
-  Dart_ExitScope();
-
   ShutdownIsolate();
   vm_isolate_ = NULL;
 
   TargetCPUFeatures::Cleanup();
-#endif
-
   Profiler::Shutdown();
   CodeObservers::DeleteAll();
 
+  ASSERT(Isolate::IsolateCount() == 0);
   return NULL;
 }
 
@@ -238,7 +237,6 @@ Isolate* Dart::CreateIsolate(const char* name_prefix,
                              const Dart_IsolateFlags& api_flags) {
   // Create a new isolate.
   Isolate* isolate = Isolate::Init(name_prefix, api_flags);
-  ASSERT(isolate != NULL);
   return isolate;
 }