Minimize enter/exit isolate calls during startup and shutdown of service isolate.

runtime/vm/service_isolate.cc

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/service_isolate.h"
 
 #include "vm/compiler.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/isolate.h"
@@ skipping 237 matching lines @@
     // Service isolate already exists.
     return;
   }
   SetServiceIsolate(I);
 }
 
 
 void ServiceIsolate::ConstructExitMessageAndCache(Isolate* I) {
   // Construct and cache exit message here so we can send it without needing an
   // isolate.
-  StartIsolateScope iso_scope(I);
   Thread* T = Thread::Current();
   ASSERT(I == T->isolate());
   ASSERT(I != NULL);
   StackZone zone(T);
   HANDLESCOPE(T);
   ASSERT(exit_message_ == NULL);
   ASSERT(exit_message_length_ == 0);
   const Array& list = Array::Handle(Z, MakeServiceExitMessage());
   ASSERT(!list.IsNull());
   MessageWriter writer(&exit_message_, &allocator, false);
@@ skipping 48 matching lines @@
                                                    &api_flags,
                                                    NULL,
                                                    &error));
     if (isolate == NULL) {
       OS::PrintErr("vm-service: Isolate creation error: %s\n", error);
       ServiceIsolate::SetServiceIsolate(NULL);
       ServiceIsolate::FinishedInitializing();
       return;
     }
 
-
-    Thread::ExitIsolate();
-
-    ServiceIsolate::ConstructExitMessageAndCache(isolate);
-
-    RunMain(isolate);
+    {
+      ASSERT(Isolate::Current() == NULL);
+      StartIsolateScope start_scope(isolate);
+      ServiceIsolate::ConstructExitMessageAndCache(isolate);
+      RunMain(isolate);
+    }
 
     ServiceIsolate::FinishedInitializing();
 
     isolate->message_handler()->Run(Dart::thread_pool(),
                                     NULL,
                                     ShutdownIsolate,
                                     reinterpret_cast<uword>(isolate));
   }
 
  protected:
   static void ShutdownIsolate(uword parameter) {
     Isolate* I = reinterpret_cast<Isolate*>(parameter);
     ASSERT(ServiceIsolate::IsServiceIsolate(I));
     ServiceIsolate::SetServiceIsolate(NULL);
     ServiceIsolate::SetServicePort(ILLEGAL_PORT);
     {
       // Print the error if there is one.  This may execute dart code to
       // print the exception object, so we need to use a StartIsolateScope.
+      ASSERT(Isolate::Current() == NULL);
       StartIsolateScope start_scope(I);
       Thread* T = Thread::Current();
       ASSERT(I == T->isolate());
       StackZone zone(T);
       HandleScope handle_scope(T);

[zra, 2015/10/30 04:47:50]

Calling Dart::ShutdownIsolate() inside of a HandleScope causes the current
thread's zone to be NULL, which will cause the assert at handles.cc:112 to fail
when we leave the handle scope. Probably that was the initial reason for
splitting up the scopes.

       Error& error = Error::Handle(Z);
       error = I->object_store()->sticky_error();
       if (!error.IsNull() && !error.IsUnwindError()) {
         OS::PrintErr("vm-service: Error: %s\n", error.ToErrorCString());
       }
       Dart::RunShutdownCallback();
-    }
-    {
+
       // Shut the isolate down.
-      SwitchIsolateScope switch_scope(I);
       Dart::ShutdownIsolate();
     }
     if (FLAG_trace_service) {
       OS::Print("vm-service: Shutdown.\n");
     }
     ServiceIsolate::FinishedExiting();
   }
 
   void RunMain(Isolate* I) {
     if (Dart::IsRunningPrecompiledCode()) {
       // TODO(24651): Remove this.
       return;
     }
-
-    StartIsolateScope iso_scope(I);
     Thread* T = Thread::Current();
     ASSERT(I == T->isolate());
     StackZone zone(T);
     HANDLESCOPE(T);
     // Invoke main which will return the loadScriptPort.
     const Library& root_library = Library::Handle(Z,
         I->object_store()->root_library());
     if (root_library.IsNull()) {
       if (FLAG_trace_service) {
         OS::Print("vm-service: Embedder did not install a script.");
@@ skipping 102 matching lines @@
   ASSERT(!result.IsNull());
   Dart_Port port = ILLEGAL_PORT;
   if (result.IsReceivePort()) {
     port = ReceivePort::Cast(result).Id();
   }
   ASSERT(port != ILLEGAL_PORT);
   ServiceIsolate::SetServicePort(port);
 }
 
 }  // namespace dart