Clear EventHandler on Stop, to avoid future usages.

runtime/bin/eventhandler.cc

 // Copyright (c) 2012, 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 "bin/dartutils.h"
 #include "bin/eventhandler.h"
 #include "bin/socket.h"
 #include "bin/thread.h"
 
 #include "include/dart_api.h"
 
 
 namespace dart {
 namespace bin {
 
-static const int kNativeEventHandlerFieldIndex = 0;
 static const intptr_t kTimerId = -1;
 static const intptr_t kInvalidId = -2;
 
 static EventHandler* event_handler = NULL;
+// TODO(ajohnsen): Consider removing mutex_ if we can enforce an invariant
+//    that eventhandler is kept alive untill all isolates are closed.
 static dart::Mutex* mutex_ = new dart::Mutex();
 
 
 void TimeoutQueue::UpdateTimeout(Dart_Port port, int64_t timeout) {
   // Find port if present.
   Timeout* last = NULL;
   Timeout* current = timeouts_;
   while (current != NULL) {
     if (current->port() == port) {
       // Found.
@@ skipping 24 matching lines @@
   while (current != NULL) {
     if (next_timeout_ == NULL ||
         current->timeout() < next_timeout_->timeout()) {
       next_timeout_ = current;
     }
     current = current->next();
   }
 }
 
 
-/*
- * Returns the reference of the EventHandler stored in the native field.
- */
-static EventHandler* GetEventHandler(Dart_Handle handle) {
-  ASSERT(event_handler != NULL);
-  return event_handler;
-}
-
 void EventHandler::Stop() {
+  MutexLocker locker(mutex_);
   if (event_handler == NULL) return;
   event_handler->Shutdown();
+  event_handler = NULL;
 }
 
 
 /*
  * Starts the EventHandler thread and stores its reference in the dart
  * EventHandler object. args[0] holds the reference to the dart EventHandler
  * object.
  */
 void FUNCTION_NAME(EventHandler_Start)(Dart_NativeArguments args) {
   MutexLocker locker(mutex_);
   if (event_handler != NULL) return;
   event_handler = EventHandler::Start();
 }
 
 
 /*
  * Send data to the EventHandler thread to register for a given instance
  * args[1] a ReceivePort args[2] with a notification event args[3]. args[0]
  * holds the reference to the dart EventHandler object.
  */
 void FUNCTION_NAME(EventHandler_SendData)(Dart_NativeArguments args) {
   Dart_EnterScope();
-  Dart_Handle handle = Dart_GetNativeArgument(args, 0);
-  EventHandler* event_handler = GetEventHandler(handle);
   Dart_Handle sender = Dart_GetNativeArgument(args, 1);
   intptr_t id = kInvalidId;
   if (Dart_IsNull(sender)) {
     id = kTimerId;
   } else {
     Socket::GetSocketIdNativeField(sender, &id);
   }
-  handle = Dart_GetNativeArgument(args, 2);
+  Dart_Handle handle = Dart_GetNativeArgument(args, 2);
   Dart_Port dart_port =
       DartUtils::GetIntegerField(handle, DartUtils::kIdFieldName);
   int64_t data = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 3));
-  event_handler->SendData(id, dart_port, data);
+  {
+    MutexLocker locker(mutex_);
+    // Only send if the event_handler is not NULL. This means that the handler
+    // shut down, and a message is send later on.
+    if (event_handler != NULL) {
+      event_handler->SendData(id, dart_port, data);
+    }
+  }
   Dart_ExitScope();
 }
 
 }  // namespace bin
 }  // namespace dart