Support tasks injection into a running VM.

src/debug.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_DEBUG_H_
 #define V8_DEBUG_H_
 
+#include <queue>
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
 #include "src/base/atomicops.h"
 #include "src/base/platform/platform.h"
 #include "src/execution.h"
 #include "src/factory.h"
 #include "src/flags.h"
 #include "src/frames-inl.h"
 #include "src/hashmap.h"
@@ skipping 299 matching lines @@
 };
 
 
 // LockingCommandMessageQueue is a thread-safe circular buffer of CommandMessage
 // messages.  The message data is not managed by LockingCommandMessageQueue.
 // Pointers to the data are passed in and out. Implemented by adding a
 // Mutex to CommandMessageQueue.  Includes logging of all puts and gets.
 class LockingCommandMessageQueue BASE_EMBEDDED {
  public:
   LockingCommandMessageQueue(Logger* logger, int size);
   bool IsEmpty() const;

[Sven Panne, 2014/12/18 08:27:51]

Not related to this CL, but anyway: Why is it safe to split Dequeue into
IsEmpty/Get here? Looking at the call sites, it's far from clear that there
can't be a race condition.

[alph, 2014/12/18 14:28:03]

While it's not related to this CL ;-), I think it is safe provided e.g.
IsEmpty/Get is used on the consumer side only. In other words once IsEmpty
returns false it keeps that state until Get is called.

   CommandMessage Get();
   void Put(const CommandMessage& message);
   void Clear();
  private:
   Logger* logger_;
   CommandMessageQueue queue_;
   mutable base::Mutex mutex_;
   DISALLOW_COPY_AND_ASSIGN(LockingCommandMessageQueue);
 };
 
 
+class LockingTaskQueue BASE_EMBEDDED {

[Sven Panne, 2014/12/18 08:27:51]

Remove BASE_EMBEDDED, it's nonsense, anyway...

[alph, 2014/12/18 14:28:03]

Done.

+ public:
+  LockingTaskQueue();
+  ~LockingTaskQueue();
+  void Enqueue(v8::Debug::Task* task);
+  v8::Debug::Task* Dequeue();
+  void Clear();
+
+ private:
+  std::queue<v8::Debug::Task*> queue_;
+  mutable base::Mutex mutex_;

[Sven Panne, 2014/12/18 08:27:51]

Without having a single const function, why do we need mutable?

[alph, 2014/12/18 14:28:03]

We don't. Removed.

+  DISALLOW_COPY_AND_ASSIGN(LockingTaskQueue);

[Sven Panne, 2014/12/18 08:27:51]

Strictly speaking this is not necessary and just noise, Mutex itself can't be
copied/assigned already.

[alph, 2014/12/18 14:28:03]

I don't want it to be depended on the set of fields. E.g. a field may change at
some point.

+};
+
+
 // This class contains the debugger support. The main purpose is to handle
 // setting break points in the code.
 //
 // This class controls the debug info for all functions which currently have
 // active breakpoints in them. This debug info is held in the heap root object
 // debug_info which is a FixedArray. Each entry in this list is of class
 // DebugInfo.
 class Debug {
  public:
   // Debug event triggers.
   void OnDebugBreak(Handle<Object> break_points_hit, bool auto_continue);
 
   void OnThrow(Handle<Object> exception, bool uncaught);
   void OnPromiseReject(Handle<JSObject> promise, Handle<Object> value);
   void OnCompileError(Handle<Script> script);
   void OnBeforeCompile(Handle<Script> script);
   void OnAfterCompile(Handle<Script> script);
   void OnPromiseEvent(Handle<JSObject> data);
   void OnAsyncTaskEvent(Handle<JSObject> data);
 
   // API facing.
   void SetEventListener(Handle<Object> callback, Handle<Object> data);
   void SetMessageHandler(v8::Debug::MessageHandler handler);
   void EnqueueCommandMessage(Vector<const uint16_t> command,
                              v8::Debug::ClientData* client_data = NULL);
   // Enqueue a debugger command to the command queue for event listeners.
   void EnqueueDebugCommand(v8::Debug::ClientData* client_data = NULL);
+  void EnqueueEmbedderTask(v8::Debug::Task* task);
+  bool ProcessEmbedderTasks();
   MUST_USE_RESULT MaybeHandle<Object> Call(Handle<JSFunction> fun,
                                            Handle<Object> data);
   Handle<Context> GetDebugContext();
   void HandleDebugBreak();
   void ProcessDebugMessages(bool debug_command_only);
 
   // Internal logic
   bool Load();
   void Break(Arguments args, JavaScriptFrame*);
   void SetAfterBreakTarget(JavaScriptFrame* frame);
@@ skipping 210 matching lines @@
   Handle<Context> debug_context_;
   Handle<Object> event_listener_;
   Handle<Object> event_listener_data_;
 
   v8::Debug::MessageHandler message_handler_;
 
   static const int kQueueInitialSize = 4;
   base::Semaphore command_received_;  // Signaled for each command received.
   LockingCommandMessageQueue command_queue_;
   LockingCommandMessageQueue event_command_queue_;
+  LockingTaskQueue embedder_task_queue_;
 
   bool is_active_;
   bool is_suppressed_;
   bool live_edit_enabled_;
   bool has_break_points_;
   bool break_disabled_;
   bool in_debug_event_listener_;
   bool break_on_exception_;
   bool break_on_uncaught_exception_;
 
@@ skipping 159 matching lines @@
   // several frames above.
   // There is no calling conventions here, because it never actually gets
   // called, it only gets returned to.
   static void GenerateFrameDropperLiveEdit(MacroAssembler* masm);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_DEBUG_H_