Revert "Simplify debugger state."

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 059c144832ffa66d21d7da85c564675b364b6c86..e3cbf326c8e533bd97702bc8285c92270d41522b 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -45,6 +45,10 @@ Debug::Debug(Isolate* isolate)
 }
 
 
+Debug::~Debug() {
+}
+
+
 static v8::Handle<v8::Context> GetDebugEventContext(Isolate* isolate) {
   Handle<Context> context = isolate->debug()->debugger_entry()->GetContext();
   // Isolate::context() may have been NULL when "script collected" event
@@ -690,7 +694,9 @@ bool Debug::CompileDebuggerScript(Isolate* isolate, int index) {
   HandleScope scope(isolate);
 
   // Bail out if the index is invalid.
-  if (index == -1) return false;
+  if (index == -1) {
+    return false;
+  }
 
   // Find source and name for the requested script.
   Handle<String> source_code =
@@ -756,11 +762,13 @@ bool Debug::Load() {
   // Return if debugger is already loaded.
   if (IsLoaded()) return true;
 
+  Debugger* debugger = isolate_->debugger();
+
   // Bail out if we're already in the process of compiling the native
   // JavaScript source code for the debugger.
-  if (isolate_->debugger()->ignore_debugger()) return false;
-  Debugger::IgnoreScope during_create(isolate_->debugger());
+  if (debugger->ignore_debugger()) return false;
 
+  Debugger::IgnoreScope during_load(debugger);
   // Disable breakpoints and interrupts while compiling and running the
   // debugger scripts including the context creation code.
   DisableBreak disable(isolate_, true);
@@ -785,13 +793,14 @@ bool Debug::Load() {
   // Expose the builtins object in the debugger context.
   Handle<String> key = isolate_->factory()->InternalizeOneByteString(
       STATIC_ASCII_VECTOR("builtins"));
-  Handle<GlobalObject> global =
-      Handle<GlobalObject>(context->global_object(), isolate_);
-  Handle<JSBuiltinsObject> builtin =
-      Handle<JSBuiltinsObject>(global->builtins(), isolate_);
+  Handle<GlobalObject> global = Handle<GlobalObject>(context->global_object());
   RETURN_ON_EXCEPTION_VALUE(
       isolate_,
-      JSReceiver::SetProperty(global, key, builtin, NONE, SLOPPY),
+      JSReceiver::SetProperty(global,
+                              key,
+                              Handle<Object>(global->builtins(), isolate_),
+                              NONE,
+                              SLOPPY),
       false);
 
   // Compile the JavaScript for the debugger in the debugger context.
@@ -803,24 +812,32 @@ bool Debug::Load() {
     caught_exception = caught_exception ||
         !CompileDebuggerScript(isolate_, Natives::GetIndex("liveedit"));
   }
+
+  // Make sure we mark the debugger as not loading before we might
+  // return.
+
   // Check for caught exceptions.
   if (caught_exception) return false;
 
+  // Debugger loaded, create debugger context global handle.
   debug_context_ = Handle<Context>::cast(
       isolate_->global_handles()->Create(*context));
+
   return true;
 }
 
 
 void Debug::Unload() {
   // Return debugger is not loaded.
-  if (!IsLoaded()) return;
+  if (!IsLoaded()) {
+    return;
+  }
 
   // Clear the script cache.
   DestroyScriptCache();
 
   // Clear debugger context global handle.
-  GlobalHandles::Destroy(Handle<Object>::cast(debug_context_).location());
+  GlobalHandles::Destroy(reinterpret_cast<Object**>(debug_context_.location()));
   debug_context_ = Handle<Context>();
 }
 
@@ -837,7 +854,7 @@ Object* Debug::Break(Arguments args) {
   JavaScriptFrame* frame = it.frame();
 
   // Just continue if breaks are disabled or debugger cannot be loaded.
-  if (disable_break()) {
+  if (disable_break() || !Load()) {
     SetAfterBreakTarget(frame);
     return heap->undefined_value();
   }
@@ -2612,7 +2629,9 @@ Debugger::Debugger(Isolate* isolate)
       is_active_(false),
       ignore_debugger_(false),
       live_edit_enabled_(true),
+      never_unload_debugger_(false),
       message_handler_(NULL),
+      debugger_unload_pending_(false),
       command_queue_(isolate->logger(), kQueueInitialSize),
       command_received_(0),
       event_command_queue_(isolate->logger(), kQueueInitialSize),
@@ -2969,17 +2988,36 @@ void Debugger::CallJSEventCallback(v8::DebugEvent event,
 
 
 Handle<Context> Debugger::GetDebugContext() {
+  never_unload_debugger_ = true;
   EnterDebugger debugger(isolate_);
   return isolate_->debug()->debug_context();
 }
 
 
+void Debugger::UnloadDebugger() {
+  Debug* debug = isolate_->debug();
+
+  // Make sure that there are no breakpoints left.
+  debug->ClearAllBreakPoints();
+
+  // Unload the debugger if feasible.
+  if (!never_unload_debugger_) {
+    debug->Unload();
+  }
+
+  // Clear the flag indicating that the debugger should be unloaded.
+  debugger_unload_pending_ = false;
+}
+
+
 void Debugger::NotifyMessageHandler(v8::DebugEvent event,
                                     Handle<JSObject> exec_state,
                                     Handle<JSObject> event_data,
                                     bool auto_continue) {
-  ASSERT(is_active_);
   HandleScope scope(isolate_);
+
+  if (!isolate_->debug()->Load()) return;
+
   // Process the individual events.
   bool sendEventMessage = false;
   switch (event) {
@@ -3107,60 +3145,77 @@ void Debugger::NotifyMessageHandler(v8::DebugEvent event,
 
 void Debugger::SetEventListener(Handle<Object> callback,
                                 Handle<Object> data) {
+  HandleScope scope(isolate_);
   GlobalHandles* global_handles = isolate_->global_handles();
 
-  // Remove existing entry.
-  GlobalHandles::Destroy(event_listener_.location());
-  event_listener_ = Handle<Object>();
-  GlobalHandles::Destroy(event_listener_data_.location());
-  event_listener_data_ = Handle<Object>();
+  // Clear the global handles for the event listener and the event listener data
+  // object.
+  if (!event_listener_.is_null()) {
+    GlobalHandles::Destroy(
+        reinterpret_cast<Object**>(event_listener_.location()));
+    event_listener_ = Handle<Object>();
+  }
+  if (!event_listener_data_.is_null()) {
+    GlobalHandles::Destroy(
+        reinterpret_cast<Object**>(event_listener_data_.location()));
+    event_listener_data_ = Handle<Object>();
+  }
 
-  // Set new entry.
+  // If there is a new debug event listener register it together with its data
+  // object.
   if (!callback->IsUndefined() && !callback->IsNull()) {
-    event_listener_ = global_handles->Create(*callback);
-    if (data.is_null()) data = isolate_->factory()->undefined_value();
-    event_listener_data_ = global_handles->Create(*data);
+    event_listener_ = Handle<Object>::cast(
+        global_handles->Create(*callback));
+    if (data.is_null()) {
+      data = isolate_->factory()->undefined_value();
+    }
+    event_listener_data_ = Handle<Object>::cast(
+        global_handles->Create(*data));
   }
 
-  UpdateState();
+  ListenersChanged();
 }
 
 
 void Debugger::SetMessageHandler(v8::Debug::MessageHandler handler) {
+  LockGuard<RecursiveMutex> with(&debugger_access_);
+
   message_handler_ = handler;
-  UpdateState();
-  if (handler == NULL && isolate_->debug()->InDebugger()) {
+  ListenersChanged();
+  if (handler == NULL) {
     // Send an empty command to the debugger if in a break to make JavaScript
     // run again if the debugger is closed.
-    EnqueueCommandMessage(Vector<const uint16_t>::empty());
+    if (isolate_->debug()->InDebugger()) {
+      EnqueueCommandMessage(Vector<const uint16_t>::empty());
+    }
   }
 }
 
 
-void Debugger::UpdateState() {
-  bool activate = message_handler_ != NULL ||
-                  !event_listener_.is_null() ||
-                  isolate_->debug()->InDebugger();
-  if (!is_active_ && activate) {
-    // Note that the debug context could have already been loaded to
-    // bootstrap test cases.
+void Debugger::ListenersChanged() {
+  LockGuard<RecursiveMutex> with(&debugger_access_);
+  is_active_ = message_handler_ != NULL || !event_listener_.is_null();
+  if (is_active_) {
+    // Disable the compilation cache when the debugger is active.
     isolate_->compilation_cache()->Disable();
-    activate = isolate_->debug()->Load();
-  } else if (is_active_ && !activate) {
+    debugger_unload_pending_ = false;
+  } else {
     isolate_->compilation_cache()->Enable();
-    isolate_->debug()->ClearAllBreakPoints();
-    isolate_->debug()->Unload();
+    // Unload the debugger if event listener and message handler cleared.
+    // Schedule this for later, because we may be in non-V8 thread.
+    debugger_unload_pending_ = true;
   }
-  is_active_ = activate;
-  // At this point the debug context is loaded iff the debugger is active.
-  ASSERT(isolate_->debug()->IsLoaded() == is_active_);
 }
 
 
 // Calls the registered debug message handler. This callback is part of the
 // public API.
 void Debugger::InvokeMessageHandler(MessageImpl message) {
-  if (message_handler_ != NULL) message_handler_(message);
+  LockGuard<RecursiveMutex> with(&debugger_access_);
+
+  if (message_handler_ != NULL) {
+    message_handler_(message);
+  }
 }
 
 
@@ -3204,6 +3259,9 @@ void Debugger::EnqueueDebugCommand(v8::Debug::ClientData* client_data) {
 
 MaybeHandle<Object> Debugger::Call(Handle<JSFunction> fun,
                                    Handle<Object> data) {
+  // When calling functions in the debugger prevent it from beeing unloaded.
+  Debugger::never_unload_debugger_ = true;
+
   // Enter the debugger.
   EnterDebugger debugger(isolate_);
   if (debugger.FailedToEnter()) {
@@ -3230,9 +3288,10 @@ MaybeHandle<Object> Debugger::Call(Handle<JSFunction> fun,
 EnterDebugger::EnterDebugger(Isolate* isolate)
     : isolate_(isolate),
       prev_(isolate_->debug()->debugger_entry()),
+      it_(isolate_),
+      has_js_frames_(!it_.done()),
       save_(isolate_) {
   Debug* debug = isolate_->debug();
-
   // Link recursive debugger entry.
   debug->set_debugger_entry(this);
 
@@ -3242,24 +3301,25 @@ EnterDebugger::EnterDebugger(Isolate* isolate)
 
   // Create the new break info. If there is no JavaScript frames there is no
   // break frame id.
-  JavaScriptFrameIterator it(isolate_);
-  has_js_frames_ = !it.done();
-  debug->NewBreak(has_js_frames_ ? it.frame()->id() : StackFrame::NO_ID);
+  if (has_js_frames_) {
+    debug->NewBreak(it_.frame()->id());
+  } else {
+    debug->NewBreak(StackFrame::NO_ID);
+  }
 
-  isolate_->debugger()->UpdateState();
   // Make sure that debugger is loaded and enter the debugger context.
-  // The previous context is kept in save_.
-  load_failed_ = !debug->IsLoaded();
-  if (!load_failed_) isolate_->set_context(*debug->debug_context());
+  load_failed_ = !debug->Load();
+  if (!load_failed_) {
+    // NOTE the member variable save which saves the previous context before
+    // this change.
+    isolate_->set_context(*debug->debug_context());
+  }
 }
 
 
 EnterDebugger::~EnterDebugger() {
   Debug* debug = isolate_->debug();
 
-  // Leaving this debugger entry.
-  debug->set_debugger_entry(prev_);
-
   // Restore to the previous break state.
   debug->SetBreak(break_frame_id_, break_id_);
 
@@ -3291,9 +3351,15 @@ EnterDebugger::~EnterDebugger() {
     if (isolate_->debugger()->HasCommands()) {
       isolate_->stack_guard()->RequestDebugCommand();
     }
+
+    // If leaving the debugger with the debugger no longer active unload it.
+    if (!isolate_->debugger()->is_active()) {
+      isolate_->debugger()->UnloadDebugger();
+    }
   }
 
-  isolate_->debugger()->UpdateState();
+  // Leaving this debugger entry.
+  debug->set_debugger_entry(prev_);
 }