TaskScheduler [13] TaskSchedulerImpl

base/task_scheduler/task_scheduler_impl.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/task_scheduler_impl.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/memory/ptr_util.h"
+#include "base/task_scheduler/sequence_sort_key.h"
+#include "base/task_scheduler/task.h"
+#include "base/time/time.h"
+
+namespace base {
+namespace internal {
+
+TaskSchedulerImpl::TaskSchedulerImpl()
+    // TODO(robliao): Wake up the service thread instead of calling DoNothing()
+    // when the delayed run time changes.
+    : delayed_task_manager_(Bind(&DoNothing))
+#if DCHECK_IS_ON()
+          ,
+      join_for_testing_returned_(true, false)
+#endif
+{
+  Initialize();
+}
+
+TaskSchedulerImpl::~TaskSchedulerImpl() {
+  // Use DLOG_ASSERT instead of DCHECK to avoid referencing
+  // |join_for_testing_returned_| in non-DCHECK builds.
+  static_assert(DCHECK_IS_ON() == ::logging::DEBUG_MODE,
+                "DCHECK_IS_ON() and ::logging::DEBUG_MODE, which defines the "
+                "behavior of DLOG_ASSERT, have diverged.");

[gab, 2016/04/28 22:44:59]

Why does that matter? The code below doesn't depend on DCHECK_IS_ON (unlike
EXPECT_DCHECK_DEATH did in that other CL)

Or is it because the other code can't be behind #if ::logging::DEBUG_MODE
because of ordering issues between precompiler rules & all?

[fdoray, 2016/04/29 13:19:49]

The definition of |join_for_testing_returned_| in task_scheduler_impl.h is
guarded by #if DCHECK_IS_ON(). It can't be guarded by #if DEBUG_MODE because
this variable is not visible by the precompiler. If ever DCHECK_IS_ON() is false
and DEBUG_MODE is true, the code below won't compile. I believe that the
static_assert above could help understand why.

+  DLOG_ASSERT(join_for_testing_returned_.IsSignaled());
+}
+
+void TaskSchedulerImpl::PostTaskWithTraits(
+    const tracked_objects::Location& from_here,
+    const TaskTraits& traits,
+    const Closure& task) {
+  // Post |task| as part of a one-off single-task Sequence.
+  GetThreadPoolForTraits(traits)->PostTaskWithSequence(
+      WrapUnique(new Task(from_here, task, traits, TimeDelta())),
+      make_scoped_refptr(new Sequence), nullptr);
+}
+
+scoped_refptr<TaskRunner> TaskSchedulerImpl::CreateTaskRunnerWithTraits(
+    const TaskTraits& traits,
+    ExecutionMode execution_mode) {
+  return GetThreadPoolForTraits(traits)->CreateTaskRunnerWithTraits(
+      traits, execution_mode);
+}
+
+void TaskSchedulerImpl::Shutdown() {
+  // TODO(fdoray): Increase the priority of BACKGROUND tasks blocking shutdown.
+  task_tracker_.Shutdown();
+}
+
+void TaskSchedulerImpl::JoinForTesting() {
+  DLOG_ASSERT(!join_for_testing_returned_.IsSignaled());
+  background_thread_pool_->JoinForTesting();
+  background_file_io_thread_pool_->JoinForTesting();
+  normal_thread_pool_->JoinForTesting();
+  normal_file_io_thread_pool_->JoinForTesting();
+#if DCHECK_IS_ON()
+  join_for_testing_returned_.Signal();
+#endif
+}
+
+void TaskSchedulerImpl::Initialize() {
+  using IORestriction = SchedulerThreadPoolImpl::IORestriction;
+
+  const SchedulerThreadPoolImpl::ReEnqueueSequenceCallback
+      re_enqueue_sequence_callback =
+          Bind(&TaskSchedulerImpl::ReEnqueueSequenceCallback, Unretained(this));
+
+  // TODO(fdoray): Derive the number of threads per pool from hardware
+  // characteristics rather than using hard-coded constants.
+
+  // Passing pointers to objects owned by |this| to
+  // SchedulerThreadPoolImpl::Create() is safe because a TaskSchedulerImpl can't
+  // be deleted before all its thread pools have been joined.
+  background_thread_pool_ = SchedulerThreadPoolImpl::Create(
+      ThreadPriority::BACKGROUND, 1U, IORestriction::DISALLOWED,
+      re_enqueue_sequence_callback, &task_tracker_, &delayed_task_manager_);
+  CHECK(background_thread_pool_);
+
+  background_file_io_thread_pool_ = SchedulerThreadPoolImpl::Create(
+      ThreadPriority::BACKGROUND, 1U, IORestriction::ALLOWED,
+      re_enqueue_sequence_callback, &task_tracker_, &delayed_task_manager_);
+  CHECK(background_file_io_thread_pool_);
+
+  normal_thread_pool_ = SchedulerThreadPoolImpl::Create(
+      ThreadPriority::NORMAL, 4U, IORestriction::DISALLOWED,
+      re_enqueue_sequence_callback, &task_tracker_, &delayed_task_manager_);
+  CHECK(normal_thread_pool_);
+
+  normal_file_io_thread_pool_ = SchedulerThreadPoolImpl::Create(
+      ThreadPriority::NORMAL, 12U, IORestriction::ALLOWED,
+      re_enqueue_sequence_callback, &task_tracker_, &delayed_task_manager_);
+  CHECK(normal_file_io_thread_pool_);
+}
+
+SchedulerThreadPool* TaskSchedulerImpl::GetThreadPoolForTraits(
+    const TaskTraits& traits) {
+  if (traits.with_file_io()) {
+    if (traits.priority() == TaskPriority::BACKGROUND)
+      return background_file_io_thread_pool_.get();
+    return normal_file_io_thread_pool_.get();
+  }
+
+  if (traits.priority() == TaskPriority::BACKGROUND)
+    return background_thread_pool_.get();
+  return normal_thread_pool_.get();
+}
+
+void TaskSchedulerImpl::ReEnqueueSequenceCallback(
+    scoped_refptr<Sequence> sequence) {
+  DCHECK(sequence);
+
+  const SequenceSortKey sort_key = sequence->GetSortKey();
+  TaskTraits traits(sequence->PeekTask()->traits);
+
+  // Update the priority of |traits| so that the next task in |sequence| runs
+  // with the highest priority in |sequence| as opposed to the next task's
+  // specific priority.
+  traits.WithPriority(sort_key.priority);
+
+  GetThreadPoolForTraits(traits)->ReEnqueueSequence(std::move(sequence),
+                                                    sort_key);
+}
+
+}  // namespace internal
+}  // namespace base