Check number of finished tasks in PageParallelJob.

BUG=chromium:609249
LOG=NO

Review-Url: https://codereview.chromium.org/1976133002
Cr-Commit-Position: refs/heads/master@{#36238}

src/heap/page-parallel-job.h

@@ -39,7 +39,8 @@ class PageParallelJob {
         items_(nullptr),
         num_items_(0),
         num_tasks_(0),
-        pending_tasks_(new base::Semaphore(0)) {}
+        pending_tasks_(new base::Semaphore(0)),
+        finished_tasks_(new base::AtomicNumber<int>(0)) {}
 
   ~PageParallelJob() {
     Item* item = items_;
@@ -49,6 +50,7 @@ class PageParallelJob {
       item = next;
     }
     delete pending_tasks_;
+    delete finished_tasks_;
   }
 
   void AddPage(MemoryChunk* chunk, typename JobTraits::PerPageData data) {
@@ -83,7 +85,7 @@ class PageParallelJob {
         start_index -= num_items_;
       }
       Task* task = new Task(heap_, items_, num_items_, start_index,
-                            pending_tasks_, per_task_data_callback(i));
+                            pending_tasks_, per_task_data_callback(i), this);
       task_ids[i] = task->id();
       if (i > 0) {
         V8::GetCurrentPlatform()->CallOnBackgroundThread(
@@ -95,12 +97,18 @@ class PageParallelJob {
     // Contribute on main thread.
     main_task->Run();
     delete main_task;
+    int aborted_tasks = 0;
     // Wait for background tasks.
     for (int i = 0; i < num_tasks_; i++) {
       if (!cancelable_task_manager_->TryAbort(task_ids[i])) {
         pending_tasks_->Wait();
+      } else {
+        ++aborted_tasks;
       }
     }
+    int finished_tasks = finished_tasks_->Value();
+    // TODO(ulan): Remove this check after investigation of crbug.com/609249.
+    CHECK_EQ(aborted_tasks + finished_tasks, num_tasks_);
     if (JobTraits::NeedSequentialFinalization) {
       Item* item = items_;
       while (item != nullptr) {
@@ -112,6 +120,8 @@ class PageParallelJob {
     }
   }
 
+  void NotifyFinishedTask() { finished_tasks_->Increment(1); }
+
  private:
   static const int kMaxNumberOfTasks = 10;
 
@@ -129,14 +139,16 @@ class PageParallelJob {
   class Task : public CancelableTask {
    public:
     Task(Heap* heap, Item* items, int num_items, int start_index,
-         base::Semaphore* on_finish, typename JobTraits::PerTaskData data)
+         base::Semaphore* on_finish, typename JobTraits::PerTaskData data,
+         PageParallelJob<JobTraits>* job)
         : CancelableTask(heap->isolate()),
           heap_(heap),
           items_(items),
           num_items_(num_items),
           start_index_(start_index),
           on_finish_(on_finish),
-          data_(data) {}
+          data_(data),
+          job_(job) {}
 
     virtual ~Task() {}
 
@@ -161,6 +173,7 @@ class PageParallelJob {
           current = items_;
         }
       }
+      job_->NotifyFinishedTask();
       on_finish_->Signal("PageParallelJob::Task::RunInternal");
     }
 
@@ -170,6 +183,7 @@ class PageParallelJob {
     int start_index_;
     base::Semaphore* on_finish_;
     typename JobTraits::PerTaskData data_;
+    PageParallelJob<JobTraits>* job_;
     DISALLOW_COPY_AND_ASSIGN(Task);
   };
 
@@ -179,6 +193,7 @@ class PageParallelJob {
   int num_items_;
   int num_tasks_;
   base::Semaphore* pending_tasks_;
+  base::AtomicNumber<int>* finished_tasks_;
   DISALLOW_COPY_AND_ASSIGN(PageParallelJob);
 };