Fix Shutdown race.

runtime/vm/isolate.h

 // Copyright (c) 2013, 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_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 405 matching lines @@
   }
 
   Dart_GcEpilogueCallback gc_epilogue_callback() const {
     return gc_epilogue_callback_;
   }
 
   void set_gc_epilogue_callback(Dart_GcEpilogueCallback callback) {
     gc_epilogue_callback_ = callback;
   }
 
+  Monitor* spawn_count_monitor() const { return spawn_count_monitor_; }
+  intptr_t* spawn_count() { return &spawn_count_; }
+
+  void IncrementSpawnCount();
+  void WaitForOutstandingSpawns();
+
   static void SetCreateCallback(Dart_IsolateCreateCallback cb) {
     create_callback_ = cb;
   }
   static Dart_IsolateCreateCallback CreateCallback() {
     return create_callback_;
   }
 
   static void SetShutdownCallback(Dart_IsolateShutdownCallback cb) {
     shutdown_callback_ = cb;
   }
@@ skipping 380 matching lines @@
   // Used to wake the isolate when it is in the pause event loop.
   Monitor* pause_loop_monitor_;
 
   // Invalidation generations; used to track events occuring in parallel
   // to background compilation. The counters may overflow, which is OK
   // since we check for equality to detect if an event occured.
   uint32_t cha_invalidation_gen_;
   uint32_t field_invalidation_gen_;
   uint32_t prefix_invalidation_gen_;
 
+  // This guards spawn_count_. An isolate cannot complete shutdown and be
+  // destroyed while there are child isolates in the midst of a spawn.
+  Monitor* spawn_count_monitor_;
+  intptr_t spawn_count_;
+
 #define ISOLATE_METRIC_VARIABLE(type, variable, name, unit)                    \
   type metric_##variable##_;
   ISOLATE_METRIC_LIST(ISOLATE_METRIC_VARIABLE);
 #undef ISOLATE_METRIC_VARIABLE
 
 #define ISOLATE_TIMELINE_STREAM_VARIABLE(name, not_used)                       \
   TimelineStream stream_##name##_;
   ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_VARIABLE)
 #undef ISOLATE_TIMELINE_STREAM_VARIABLE
 
@@ skipping 74 matching lines @@
 };
 
 
 class IsolateSpawnState {
  public:
   IsolateSpawnState(Dart_Port parent_port,
                     Dart_Port origin_id,
                     void* init_data,
                     const Function& func,
                     const Instance& message,
+                    Monitor* spawn_count_monitor,
+                    intptr_t* spawn_count,
                     bool paused,
                     bool errorsAreFatal,
                     Dart_Port onExit,
                     Dart_Port onError);
   IsolateSpawnState(Dart_Port parent_port,
                     void* init_data,
                     const char* script_url,
                     const char* package_root,
                     const char** package_map,
                     const Instance& args,
                     const Instance& message,
+                    Monitor* spawn_count_monitor,
+                    intptr_t* spawn_count,
                     bool paused,
                     bool errorsAreFatal,
                     Dart_Port onExit,
                     Dart_Port onError);
   ~IsolateSpawnState();
 
   Isolate* isolate() const { return isolate_; }
   void set_isolate(Isolate* value) { isolate_ = value; }
 
   Dart_Port parent_port() const { return parent_port_; }
   Dart_Port origin_id() const { return origin_id_; }
   void* init_data() const { return init_data_; }
   Dart_Port on_exit_port() const { return on_exit_port_; }
   Dart_Port on_error_port() const { return on_error_port_; }
   const char* script_url() const { return script_url_; }
   const char* package_root() const { return package_root_; }
   const char** package_map() const { return package_map_; }
   const char* library_url() const { return library_url_; }
   const char* class_name() const { return class_name_; }
   const char* function_name() const { return function_name_; }
   bool is_spawn_uri() const { return library_url_ == NULL; }
   bool paused() const { return paused_; }
   bool errors_are_fatal() const { return errors_are_fatal_; }
   Isolate::Flags* isolate_flags() { return &isolate_flags_; }
 
   RawObject* ResolveFunction();
   RawInstance* BuildArgs(Thread* thread);
   RawInstance* BuildMessage(Thread* thread);
 
+  void DecrementSpawnCount();
+
  private:
   Isolate* isolate_;
   Dart_Port parent_port_;
   Dart_Port origin_id_;
   void* init_data_;
   Dart_Port on_exit_port_;
   Dart_Port on_error_port_;
   const char* script_url_;
   const char* package_root_;
   const char** package_map_;
   const char* library_url_;
   const char* class_name_;
   const char* function_name_;
   uint8_t* serialized_args_;
   intptr_t serialized_args_len_;
   uint8_t* serialized_message_;
   intptr_t serialized_message_len_;
+
+  // This counter tracks the number of outstanding calls to spawn by the parent
+  // isolate.
+  Monitor* spawn_count_monitor_;
+  intptr_t* spawn_count_;
+
   Isolate::Flags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_