- Implement Isolate.pause and Isolate.resume.

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/message.h"
 #include "vm/thread.h"
 #include "vm/thread_pool.h"
@@ skipping 53 matching lines @@
   bool HasLivePorts() const { return live_ports_ > control_ports_; }
 
   intptr_t live_ports() const {
     return live_ports_;
   }
 
   intptr_t control_ports() const {
     return control_ports_;
   }
 
+  bool paused() const { return paused_ > 0; }
+
+  void increment_paused() { paused_++; }

[siva, 2014/07/01 21:42:56]

How do we ensure paused does not overflow?

[Lasse Reichstein Nielsen, 2014/07/02 08:11:55]

If paused_ is an intptr_t, and we store one resumeCapability per pause, we will
definitely run out of memory before it overflows.

[siva, 2014/07/02 14:52:10]

True but instead of relying on that one needs to set a max possible value for
this and check against that max like we do in all other similar scenarios in the
VM. That is the recommended guideline from the security folks.

[Ivan Posva, 2014/07/03 12:51:17]

Isolate::AddResumeCapability now prevents overflows of this counter by
calculating a maximum allowable number of capabilities recorded and not growing
once that number is reached.

+  void decrement_paused() { paused_--; }

[siva, 2014/07/01 21:42:56]

ASSERT(paused_ > 0);

[Ivan Posva, 2014/07/03 12:51:17]

Done.

+
   bool pause_on_start() const {
     return pause_on_start_;
   }
 
   void set_pause_on_start(bool pause_on_start) {
     pause_on_start_ = pause_on_start;
   }
 
   bool paused_on_start() const {
     // If pause_on_start_ is still set, tell the user we are paused,
@@ skipping 73 matching lines @@
 
   // Handles any pending messages.
   bool HandleMessages(bool allow_normal_messages,
                       bool allow_multiple_normal_messages);
 
   Monitor monitor_;  // Protects all fields in MessageHandler.
   MessageQueue* queue_;
   MessageQueue* oob_queue_;
   intptr_t control_ports_;  // The number of open control ports usually 0 or 1.
   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_exit_;
   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_