[heap] Reland "Cancel tasks before tearing down the heap."

src/cancelable-task.cc

 // Copyright 2015 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/cancelable-task.h"
 
 #include "src/base/platform/platform.h"
 #include "src/isolate.h"
 
 namespace v8 {
 namespace internal {
 
 
 Cancelable::Cancelable(CancelableTaskManager* parent)
     : parent_(parent), status_(kWaiting), id_(0), cancel_counter_(0) {
   id_ = parent->Register(this);
 }
 
 
 Cancelable::~Cancelable() {
   // The following check is needed to avoid calling an already terminated
   // manager object. This happens when the manager cancels all pending tasks
   // in {CancelAndWait} only before destroying the manager object.
   if (TryRun() || IsRunning()) {
     parent_->RemoveFinishedTask(id_);
   }
 }
 
-CancelableTaskManager::CancelableTaskManager() : task_id_counter_(0) {}
+CancelableTaskManager::CancelableTaskManager()
+    : task_id_counter_(0), canceled_(false) {}
 
 uint32_t CancelableTaskManager::Register(Cancelable* task) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   uint32_t id = ++task_id_counter_;
   // The loop below is just used when task_id_counter_ overflows.
   while (cancelable_tasks_.count(id) > 0) ++id;
+  CHECK(!canceled_);
   cancelable_tasks_[id] = task;
   return id;
 }
 
 
 void CancelableTaskManager::RemoveFinishedTask(uint32_t id) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   size_t removed = cancelable_tasks_.erase(id);
   USE(removed);
   DCHECK_NE(0, removed);
@@ skipping 16 matching lines @@
   return false;
 }
 
 
 void CancelableTaskManager::CancelAndWait() {
   // Clean up all cancelable fore- and background tasks. Tasks are canceled on
   // the way if possible, i.e., if they have not started yet.  After each round
   // of canceling we wait for the background tasks that have already been
   // started.
   base::LockGuard<base::Mutex> guard(&mutex_);
+  canceled_ = true;
 
   // Cancelable tasks could be running or could potentially register new
   // tasks, requiring a loop here.
   while (!cancelable_tasks_.empty()) {
     for (auto it = cancelable_tasks_.begin(); it != cancelable_tasks_.end();) {
       auto current = it;
       // We need to get to the next element before erasing the current.
       ++it;
       if (current->second->Cancel()) {
         cancelable_tasks_.erase(current);
       }
     }
     // Wait for already running background tasks.
     if (!cancelable_tasks_.empty()) {
       cancelable_tasks_barrier_.Wait(&mutex_);
     }
   }
 }
 
 
 CancelableTask::CancelableTask(Isolate* isolate)
     : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 
 CancelableIdleTask::CancelableIdleTask(Isolate* isolate)
     : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 }  // namespace internal
 }  // namespace v8