Prevent liveedit on or under generators with open activations

src/liveedit.cc

 // 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.
 
 
 #include "v8.h"
 
 #include "liveedit.h"
 
 #include "code-stubs.h"
@@ skipping 1637 matching lines @@
   for (Address a = unused_stack_top;
       a < unused_stack_bottom;
       a += kPointerSize) {
     Memory::Object_at(a) = Smi::FromInt(0);
   }
 
   return NULL;
 }
 
 
-static bool IsDropableFrame(StackFrame* frame) {
-  return !frame->is_exit();
-}
-
-
 // Describes a set of call frames that execute any of listed functions.
 // Finding no such frames does not mean error.
 class MultipleFunctionTarget {
  public:
   MultipleFunctionTarget(Handle<JSArray> shared_info_array,
       Handle<JSArray> result)
       : m_shared_info_array(shared_info_array),
         m_result(result) {}
   bool MatchActivation(StackFrame* frame,
       LiveEdit::FunctionPatchabilityStatus status) {
@@ skipping 33 matching lines @@
     }
   }
 
   if (top_frame_index == -1) {
     // We haven't found break frame, but no function is blocking us anyway.
     return target.GetNotFoundMessage();
   }
 
   bool target_frame_found = false;
   int bottom_js_frame_index = top_frame_index;
-  bool c_code_found = false;
+  bool non_droppable_frame_found = false;
+  LiveEdit::FunctionPatchabilityStatus non_droppable_reason;
 
   for (; frame_index < frames.length(); frame_index++) {
     StackFrame* frame = frames[frame_index];
-    if (!IsDropableFrame(frame)) {
-      c_code_found = true;
+    if (frame->is_exit()) {
+      non_droppable_frame_found = true;
+      non_droppable_reason = LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE;
+      break;
+    }
+    if (!frame->is_java_script()) continue;
+    if (JavaScriptFrame::cast(frame)->function()->shared()->is_generator()) {
+      non_droppable_frame_found = true;
+      non_droppable_reason = LiveEdit::FUNCTION_BLOCKED_UNDER_GENERATOR;
       break;
     }
     if (target.MatchActivation(
             frame, LiveEdit::FUNCTION_BLOCKED_ON_ACTIVE_STACK)) {
       target_frame_found = true;
       bottom_js_frame_index = frame_index;
     }
   }
 
-  if (c_code_found) {
-    // There is a C frames on stack. Check that there are no target frames
-    // below them.
+  if (non_droppable_frame_found) {
+    // There is a C or generator frame on stack.  We can't drop C frames, and we
+    // can't restart generators.  Check that there are no target frames below
+    // them.
     for (; frame_index < frames.length(); frame_index++) {
       StackFrame* frame = frames[frame_index];
       if (frame->is_java_script()) {
-        if (target.MatchActivation(
-                frame, LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE)) {
-          // Cannot drop frame under C frames.
+        if (target.MatchActivation(frame, non_droppable_reason)) {
+          // Fail.
           return NULL;
         }
       }
     }
   }
 
   if (!do_drop) {
     // We are in check-only mode.
     return NULL;
   }
@@ skipping 49 matching lines @@
     if (*obj == Smi::FromInt(LiveEdit::FUNCTION_BLOCKED_ON_ACTIVE_STACK)) {
       Handle<Object> replaced(
           Smi::FromInt(LiveEdit::FUNCTION_REPLACED_ON_ACTIVE_STACK), isolate);
       SetElementSloppy(result, i, replaced);
     }
   }
   return NULL;
 }
 
 
+bool LiveEdit::FindActiveGenerators(Handle<FixedArray> shared_info_array,
+                                    Handle<FixedArray> result, int len) {

[Yang, 2014/05/06 13:05:03]

one argument per line is easier on the eye.

+  Isolate* isolate = shared_info_array->GetIsolate();
+  Heap* heap = isolate->heap();
+  heap->EnsureHeapIsIterable();
+  bool found_suspended_activations = false;
+
+  ASSERT_LE(len, result->length());
+
+  DisallowHeapAllocation no_allocation;
+
+  FunctionPatchabilityStatus active = FUNCTION_BLOCKED_ACTIVE_GENERATOR;
+
+  HeapIterator iterator(heap);
+  HeapObject* obj = NULL;
+  while (((obj = iterator.next()) != NULL)) {

[Yang, 2014/05/06 13:05:03]

I think we can remove one set of brackets here.

+    if (!obj->IsJSGeneratorObject()) continue;
+
+    JSGeneratorObject* gen = JSGeneratorObject::cast(obj);
+    if (gen->is_closed()) continue;
+
+    HandleScope scope(isolate);
+
+    for (int i = 0; i < len; i++) {
+      Handle<JSValue> jsvalue =
+          Handle<JSValue>::cast(FixedArray::get(shared_info_array, i));
+      Handle<SharedFunctionInfo> shared =
+          UnwrapSharedFunctionInfoFromJSValue(jsvalue);
+
+      if (gen->function()->shared() == *shared) {
+        result->set(i, Smi::FromInt(active));
+        found_suspended_activations = true;
+      }
+    }
+  }
+
+  return found_suspended_activations;
+}
+
+
 class InactiveThreadActivationsChecker : public ThreadVisitor {
  public:
   InactiveThreadActivationsChecker(Handle<JSArray> shared_info_array,
                                    Handle<JSArray> result)
       : shared_info_array_(shared_info_array), result_(result),
         has_blocked_functions_(false) {
   }
   void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
     for (StackFrameIterator it(isolate, top); !it.done(); it.Advance()) {
       has_blocked_functions_ |= CheckActivation(
@@ skipping 10 matching lines @@
   Handle<JSArray> result_;
   bool has_blocked_functions_;
 };
 
 
 Handle<JSArray> LiveEdit::CheckAndDropActivations(
     Handle<JSArray> shared_info_array, bool do_drop) {
   Isolate* isolate = shared_info_array->GetIsolate();
   int len = GetArrayLength(shared_info_array);
 
+  CHECK(shared_info_array->HasFastElements());
+  Handle<FixedArray> shared_info_array_elements(
+      FixedArray::cast(shared_info_array->elements()));
+
   Handle<JSArray> result = isolate->factory()->NewJSArray(len);
+  Handle<FixedArray> result_elements =
+      JSObject::EnsureWritableFastElements(result);
 
   // Fill the default values.
   for (int i = 0; i < len; i++) {
-    SetElementSloppy(
-        result,
-        i,
-        Handle<Smi>(Smi::FromInt(FUNCTION_AVAILABLE_FOR_PATCH), isolate));
+    FunctionPatchabilityStatus status = FUNCTION_AVAILABLE_FOR_PATCH;
+    result_elements->set(i, Smi::FromInt(status));
   }
 
+  // Scan the heap for active generators -- those that are either currently
+  // running (as we wouldn't want to restart them, because we don't know where
+  // to restart them from) or suspended.  Fail if any one corresponds to the set
+  // of functions being edited.
+  if (FindActiveGenerators(shared_info_array_elements, result_elements, len))

[Yang, 2014/05/06 13:05:03]

please use curly brackets if the if-statement contains a line break.

+    return result;
 
-  // First check inactive threads. Fail if some functions are blocked there.
+  // Check inactive threads. Fail if some functions are blocked there.
   InactiveThreadActivationsChecker inactive_threads_checker(shared_info_array,
                                                             result);
   isolate->thread_manager()->IterateArchivedThreads(
       &inactive_threads_checker);
   if (inactive_threads_checker.HasBlockedFunctions()) {
     return result;
   }
 
   // Try to drop activations from the current stack.
   const char* error_message =
@@ skipping 42 matching lines @@
   SingleFrameTarget target(frame);
 
   const char* result = DropActivationsInActiveThreadImpl(
       frame->isolate(), target, true);
   if (result != NULL) {
     return result;
   }
   if (target.saved_status() == LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE) {
     return "Function is blocked under native code";
   }
+  if (target.saved_status() == LiveEdit::FUNCTION_BLOCKED_UNDER_GENERATOR) {
+    return "Function is blocked under a generator activation";
+  }
   return NULL;
 }
 
 
 LiveEditFunctionTracker::LiveEditFunctionTracker(Isolate* isolate,
                                                  FunctionLiteral* fun)
     : isolate_(isolate) {
   if (isolate_->active_function_info_listener() != NULL) {
     isolate_->active_function_info_listener()->FunctionStarted(fun);
   }
@@ skipping 20 matching lines @@
 void LiveEditFunctionTracker::RecordRootFunctionInfo(Handle<Code> code) {
   isolate_->active_function_info_listener()->FunctionCode(code);
 }
 
 
 bool LiveEditFunctionTracker::IsActive(Isolate* isolate) {
   return isolate->active_function_info_listener() != NULL;
 }
 
 } }  // namespace v8::internal