[heap] Implement concurrent marking boilerplate.

src/heap/concurrent-marking.cc

+// Copyright 2017 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 "src/heap/concurrent-marking.h"
+
+#include "src/heap/heap-inl.h"
+#include "src/heap/heap.h"
+#include "src/isolate.h"
+#include "src/locked-queue-inl.h"
+#include "src/v8.h"
+
+namespace v8 {
+namespace internal {
+
+class ConcurrentMarking::Task : public CancelableTask {
+ public:
+  Task(Heap* heap, Queue* queue, base::Semaphore* on_finish)
+      : CancelableTask(heap->isolate()),
+        heap_(heap),
+        queue_(queue),
+        on_finish_(on_finish) {}
+
+  virtual ~Task() {}
+
+ private:
+  // v8::internal::CancelableTask overrides.
+  void RunInternal() override {
+    USE(heap_);
+    HeapObject* object;
+    while (queue_->Dequeue(&object)) {
+      // TODO(ulan): Implement actual marking.
+    }
+    on_finish_->Signal();
+  }
+
+  Heap* heap_;
+  Queue* queue_;
+  base::Semaphore* on_finish_;
+  DISALLOW_COPY_AND_ASSIGN(Task);
+};
+
+ConcurrentMarking::ConcurrentMarking(Heap* heap)
+    : heap_(heap), pending_tasks_(0), number_of_tasks_(0) {}
+
+ConcurrentMarking::~ConcurrentMarking() {}
+
+void ConcurrentMarking::EnqueueObject(HeapObject* object) {
+  queue_.Enqueue(object);
+}
+
+bool ConcurrentMarking::IsQueueEmpty() { return queue_.IsEmpty(); }
+
+void ConcurrentMarking::StartMarkingTasks(int number_of_tasks) {
+  if (!FLAG_concurrent_marking) return;
+  DCHECK_EQ(0, number_of_tasks_);
+
+  number_of_tasks_ = number_of_tasks;
+  for (int i = 0; i < number_of_tasks; i++) {
+    V8::GetCurrentPlatform()->CallOnBackgroundThread(
+        new Task(heap_, &queue_, &pending_tasks_),
+        v8::Platform::kShortRunningTask);
+  }
+}
+
+void ConcurrentMarking::WaitForTasksToComplete() {
+  if (!FLAG_concurrent_marking) return;
+
+  CancelableTaskManager* cancelable_task_manager =
+      heap_->isolate()->cancelable_task_manager();
+  for (int i = 0; i < number_of_tasks_; i++) {
+    if (cancelable_task_manager->TryAbort(task_ids_[i]) !=
+        CancelableTaskManager::kTaskAborted) {
+      pending_tasks_.Wait();
+    }
+  }
+  number_of_tasks_ = 0;
+}
+
+}  // namespace internal
+}  // namespace v8