Reference CL for the new task scheduler.

base/task_scheduler/shutdown_manager.cc

+// Copyright 2016 The Chromium 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 "base/task_scheduler/shutdown_manager.h"
+
+#include "base/atomicops.h"
+
+namespace base {
+namespace internal {
+
+ShutdownManager::ShutdownManager()
+    : cv_(lock_.RawLockForConditionVariable()),
+      num_tasks_blocking_shutdown_(0),
+      is_shutting_down_(false),
+      shutdown_completed_(false) {
+  subtle::MemoryBarrier();
+}
+
+void ShutdownManager::Shutdown() {
+  AutoSchedulerLock auto_lock(lock_);
+
+  DCHECK(!is_shutting_down_) << "ShutdownManager::Shutdown can't be called "
+                                "simultaneously on multiple threads.";
+  is_shutting_down_ = true;
+
+  // Wait until the number of tasks blocking shutdown is zero.
+  while (num_tasks_blocking_shutdown_ != 0)
+    cv_.Wait();
+
+  is_shutting_down_ = false;
+  shutdown_completed_ = true;
+}
+
+bool ShutdownManager::ShouldPostTask(TaskShutdownBehavior shutdown_behavior) {
+  AutoSchedulerLock auto_lock(lock_);
+
+  if (shutdown_completed_)
+    return false;
+
+  if (shutdown_behavior == TaskShutdownBehavior::BLOCK_SHUTDOWN) {
+    ++num_tasks_blocking_shutdown_;
+    return true;
+  }
+
+  return !is_shutting_down_;
+}
+
+bool ShutdownManager::ShouldScheduleTask(
+    TaskShutdownBehavior shutdown_behavior) {
+  AutoSchedulerLock auto_lock(lock_);
+
+  if (shutdown_completed_)
+    return false;
+
+  switch (shutdown_behavior) {
+    case TaskShutdownBehavior::BLOCK_SHUTDOWN: {
+      return true;
+    }
+
+    case TaskShutdownBehavior::SKIP_ON_SHUTDOWN: {
+      if (is_shutting_down_)
+        return false;
+      ++num_tasks_blocking_shutdown_;
+      return true;
+    }
+
+    case TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN: {
+      return !is_shutting_down_;
+    }
+
+    default: {
+      NOTREACHED();
+      return false;
+    }
+  }
+}
+
+void ShutdownManager::DidExecuteTask(TaskShutdownBehavior shutdown_behavior) {
+  if (shutdown_behavior == TaskShutdownBehavior::BLOCK_SHUTDOWN ||
+      shutdown_behavior == TaskShutdownBehavior::SKIP_ON_SHUTDOWN) {
+    AutoSchedulerLock auto_lock(lock_);
+    --num_tasks_blocking_shutdown_;
+    if (num_tasks_blocking_shutdown_ == 0)
+      cv_.Signal();
+  }
+}
+
+void ShutdownManager::set_is_shutting_down_for_testing(bool is_shutting_down) {
+  is_shutting_down_ = is_shutting_down;
+}
+
+bool ShutdownManager::is_shutting_down_for_testing() const {
+  subtle::MemoryBarrier();
+  return is_shutting_down_;
+}
+
+bool ShutdownManager::shutdown_completed() const {
+  subtle::MemoryBarrier();
+  return shutdown_completed_;
+}
+
+}  // namespace internal
+}  // namespace base