VM restart + shutdown fixes

runtime/vm/message_handler.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_MESSAGE_HANDLER_H_
 #define VM_MESSAGE_HANDLER_H_
 
 #include "vm/isolate.h"
 #include "vm/message.h"
 #include "vm/os_thread.h"
 #include "vm/thread_pool.h"
 
 namespace dart {
 
 // A MessageHandler is an entity capable of accepting messages.
 class MessageHandler {
  protected:
   MessageHandler();
 
  public:
+  enum MessageStatus {
+    kOK,        // We successfully handled a message.
+    kError,     // We encountered an error handling a message.
+    kRestart,   // The VM is restarting.
+    kShutdown,  // The VM is shutting down.
+  };
+
   virtual ~MessageHandler();
 
   // Allow subclasses to provide a handler name.
   virtual const char* name() const;
 
   typedef uword CallbackData;
-  typedef bool (*StartCallback)(CallbackData data);
+  typedef MessageStatus (*StartCallback)(CallbackData data);
   typedef void (*EndCallback)(CallbackData data);
 
   // Runs this message handler on the thread pool.
   //
   // Before processing messages, the optional StartFunction is run.
   //
   // A message handler will run until it terminates either normally or
   // abnormally.  Normal termination occurs when the message handler
   // no longer has any live ports.  Abnormal termination occurs when
   // HandleMessage() indicates that an error has occurred during
   // message processing.
   void Run(ThreadPool* pool,
            StartCallback start_callback,
            EndCallback end_callback,
            CallbackData data);
 
   // Handles the next message for this message handler.  Should only
   // be used when not running the handler on the thread pool (via Run
   // or RunBlocking).
   //
   // Returns true on success.
-  bool HandleNextMessage();
+  MessageStatus HandleNextMessage();
 
   // Handles any OOB messages for this message handler.  Can be used
   // even if the message handler is running on the thread pool.
   //
   // Returns true on success.
-  bool HandleOOBMessages();
+  MessageStatus HandleOOBMessages();
 
   // Returns true if there are pending OOB messages for this message
   // handler.
   bool HasOOBMessages();
 
   // A message handler tracks how many live ports it has.
   bool HasLivePorts() const { return live_ports_ > 0; }
 
   intptr_t live_ports() const {
     return live_ports_;
@@ skipping 106 matching lines @@
   void increment_live_ports();
   void decrement_live_ports();
   // ------------ END PortMap API ------------
 
   // Custom message notification.  Optionally provided by subclass.
   virtual void MessageNotify(Message::Priority priority);
 
   // Handles a single message.  Provided by subclass.
   //
   // Returns true on success.
-  virtual bool HandleMessage(Message* message) = 0;
+  virtual MessageStatus HandleMessage(Message* message) = 0;
 
   virtual void NotifyPauseOnStart() {}
   virtual void NotifyPauseOnExit() {}
 
   // TODO(iposva): Set a local field before entering MessageHandler methods.
   Thread* thread() const { return Thread::Current(); }
 
  private:
   friend class PortMap;
   friend class MessageHandlerTestPeer;
   friend class MessageHandlerTask;
 
   // Called by MessageHandlerTask to process our task queue.
   void TaskCallback();
 
   // Dequeue the next message.  Prefer messages from the oob_queue_ to
   // messages from the queue_.
   Message* DequeueMessage(Message::Priority min_priority);
 
+  void ClearOOBQueue();
+
   // Handles any pending messages.
-  bool HandleMessages(bool allow_normal_messages,
-                      bool allow_multiple_normal_messages);
+  MessageStatus HandleMessages(bool allow_normal_messages,
+                               bool allow_multiple_normal_messages);
 
   Monitor monitor_;  // Protects all fields in MessageHandler.
   MessageQueue* queue_;
   MessageQueue* oob_queue_;
   // This flag is not thread safe and can only reliably be accessed on a single
   // thread.
   bool oob_message_handling_allowed_;
   intptr_t live_ports_;  // The number of open ports, including control ports.
   intptr_t paused_;  // The number of pause messages received.
   bool pause_on_start_;
   bool pause_on_exit_;
   bool paused_on_start_;
   bool paused_on_exit_;
   int64_t paused_timestamp_;
   ThreadPool* pool_;
   ThreadPool::Task* task_;
   StartCallback start_callback_;
   EndCallback end_callback_;
   CallbackData callback_data_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageHandler);
 };
 
 }  // namespace dart
 
 #endif  // VM_MESSAGE_HANDLER_H_