Revert of scheduler: Add a base directory

components/scheduler/child/task_queue_manager.h

+// Copyright 2014 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.
+
+#ifndef CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
+#define CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
+
+#include <map>
+
+#include "base/atomic_sequence_num.h"
+#include "base/debug/task_annotator.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/message_loop/message_loop.h"
+#include "base/pending_task.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/thread_checker.h"
+#include "components/scheduler/child/task_queue_impl.h"
+#include "components/scheduler/child/task_queue_selector.h"
+#include "components/scheduler/scheduler_export.h"
+
+namespace base {
+class TickClock;
+
+namespace trace_event {
+class ConvertableToTraceFormat;
+class TracedValue;
+}  // namespace trace_event
+}  // namespace base
+
+namespace scheduler {
+namespace internal {
+class LazyNow;
+class TaskQueueImpl;
+}  // namespace internal
+
+class NestableSingleThreadTaskRunner;
+
+// The task queue manager provides N task queues and a selector interface for
+// choosing which task queue to service next. Each task queue consists of two
+// sub queues:
+//
+// 1. Incoming task queue. Tasks that are posted get immediately appended here.
+//    When a task is appended into an empty incoming queue, the task manager
+//    work function (DoWork) is scheduled to run on the main task runner.
+//
+// 2. Work queue. If a work queue is empty when DoWork() is entered, tasks from
+//    the incoming task queue (if any) are moved here. The work queues are
+//    registered with the selector as input to the scheduling decision.
+//
+class SCHEDULER_EXPORT TaskQueueManager
+    : public internal::TaskQueueSelector::Observer {
+ public:
+  // Create a task queue manager where |main_task_runner| identifies the thread
+  // on which where the tasks are  eventually run. Category strings must have
+  // application lifetime (statics or literals). They may not include " chars.
+  TaskQueueManager(
+      scoped_refptr<NestableSingleThreadTaskRunner> main_task_runner,
+      const char* disabled_by_default_tracing_category,
+      const char* disabled_by_default_verbose_tracing_category);
+  ~TaskQueueManager() override;
+
+  // Returns the time of the next pending delayed task in any queue.  Ignores
+  // any delayed tasks whose delay has expired. Returns a null TimeTicks object
+  // if no tasks are pending.  NOTE this is somewhat expensive since every queue
+  // will get locked.
+  base::TimeTicks NextPendingDelayedTaskRunTime();
+
+  // Set the number of tasks executed in a single invocation of the task queue
+  // manager. Increasing the batch size can reduce the overhead of yielding
+  // back to the main message loop -- at the cost of potentially delaying other
+  // tasks posted to the main loop. The batch size is 1 by default.
+  void SetWorkBatchSize(int work_batch_size);
+
+  // These functions can only be called on the same thread that the task queue
+  // manager executes its tasks on.
+  void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer);
+  void RemoveTaskObserver(base::MessageLoop::TaskObserver* task_observer);
+
+  void SetTimeSourceForTesting(scoped_ptr<base::TickClock> time_source);
+
+  // Returns true if any task from a monitored task queue was was run since the
+  // last call to GetAndClearSystemIsQuiescentBit.
+  bool GetAndClearSystemIsQuiescentBit();
+
+  // Creates a task queue with the given |spec|.  Must be called on the thread
+  // this class was created on.
+  scoped_refptr<internal::TaskQueueImpl> NewTaskQueue(
+      const TaskQueue::Spec& spec);
+
+  class SCHEDULER_EXPORT Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called when |queue| is unregistered.
+    virtual void OnUnregisterTaskQueue(
+        const scoped_refptr<internal::TaskQueueImpl>& queue) = 0;
+  };
+
+  // Called once to set the Observer. This function is called on the main
+  // thread. If |observer| is null, then no callbacks will occur.
+  // Note |observer| is expected to outlive the SchedulerHelper.
+  void SetObserver(Observer* observer);
+
+ private:
+  friend class internal::LazyNow;
+  friend class internal::TaskQueueImpl;
+  friend class TaskQueueManagerTest;
+
+  class DeletionSentinel : public base::RefCounted<DeletionSentinel> {
+   private:
+    friend class base::RefCounted<DeletionSentinel>;
+    ~DeletionSentinel() {}
+  };
+
+  // Unregisters a TaskQueue previously created by |NewTaskQueue()|.
+  // NOTE we have to flush the queue from |newly_updatable_| which means as a
+  // side effect MoveNewlyUpdatableQueuesIntoUpdatableQueueSet is called by this
+  // function.
+  void UnregisterTaskQueue(scoped_refptr<internal::TaskQueueImpl> task_queue);
+
+  // TaskQueueSelector::Observer implementation:
+  void OnTaskQueueEnabled(internal::TaskQueueImpl* queue) override;
+
+  // Called by the task queue to register a new pending task.
+  void DidQueueTask(const internal::TaskQueueImpl::Task& pending_task);
+
+  // Post a task to call DoWork() on the main task runner.  Only one pending
+  // DoWork is allowed from the main thread, to prevent an explosion of pending
+  // DoWorks.
+  void MaybePostDoWorkOnMainRunner();
+
+  // Use the selector to choose a pending task and run it.
+  void DoWork(bool decrement_pending_dowork_count);
+
+  // Delayed Tasks with run_times <= Now() are enqueued onto the work queue.
+  // Reloads any empty work queues which have automatic pumping enabled and
+  // which are eligible to be auto pumped based on the |previous_task| which was
+  // run and |should_trigger_wakeup|. Call with an empty |previous_task| if no
+  // task was just run.
+  void UpdateWorkQueues(bool should_trigger_wakeup,
+                        const internal::TaskQueueImpl::Task* previous_task);
+
+  // Chooses the next work queue to service. Returns true if |out_queue|
+  // indicates the queue from which the next task should be run, false to
+  // avoid running any tasks.
+  bool SelectQueueToService(internal::TaskQueueImpl** out_queue);
+
+  // Runs a single nestable task from the |queue|. On exit, |out_task| will
+  // contain the task which was executed. Non-nestable task are reposted on the
+  // run loop. The queue must not be empty.
+  enum class ProcessTaskResult {
+    DEFERRED,
+    EXECUTED,
+    TASK_QUEUE_MANAGER_DELETED
+  };
+  ProcessTaskResult ProcessTaskFromWorkQueue(
+      internal::TaskQueueImpl* queue,
+      internal::TaskQueueImpl::Task* out_previous_task);
+
+  bool RunsTasksOnCurrentThread() const;
+  bool PostDelayedTask(const tracked_objects::Location& from_here,
+                       const base::Closure& task,
+                       base::TimeDelta delay);
+  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
+                                  const base::Closure& task,
+                                  base::TimeDelta delay);
+
+  base::TimeTicks Now() const;
+
+  int GetNextSequenceNumber();
+
+  scoped_refptr<base::trace_event::ConvertableToTraceFormat>
+  AsValueWithSelectorResult(bool should_run,
+                            internal::TaskQueueImpl* selected_queue) const;
+
+  // Causes DoWork to start calling UpdateWorkQueue for |queue|. Can be called
+  // from any thread.
+  void RegisterAsUpdatableTaskQueue(internal::TaskQueueImpl* queue);
+
+  // Prevents DoWork from calling UpdateWorkQueue for |queue|. Must be called
+  // from the thread the TaskQueueManager was created on.
+  void UnregisterAsUpdatableTaskQueue(internal::TaskQueueImpl* queue);
+
+  // Schedule a call to DelayedDoWork at |delayed_run_time| which will call
+  // TaskQueueImpl::MoveReadyDelayedTasksToIncomingQueue for |queue|.
+  // Can be called from any thread.
+  void ScheduleDelayedWork(internal::TaskQueueImpl* queue,
+                           base::TimeTicks delayed_run_time,
+                           internal::LazyNow* lazy_now);
+
+  // Function calling ScheduleDelayedWork that's suitable for use in base::Bind.
+  void ScheduleDelayedWorkTask(scoped_refptr<internal::TaskQueueImpl> queue,
+                               base::TimeTicks delayed_run_time);
+
+  // Calls WakeupReadyDelayedQueues followed by DoWork so that ready delayed
+  // tasks are enqueued and run. Must be called from the main thread.
+  void DelayedDoWork();
+
+  // Call TaskQueueImpl::MoveReadyDelayedTasksToIncomingQueue for each
+  // registered queue for which the delay has elapsed.
+  void WakeupReadyDelayedQueues(internal::LazyNow* lazy_now);
+
+  void MoveNewlyUpdatableQueuesIntoUpdatableQueueSet();
+
+  std::set<scoped_refptr<internal::TaskQueueImpl>> queues_;
+
+  // We have to be careful when deleting a queue because some of the code uses
+  // raw pointers and doesn't expect the rug to be pulled out from underneath.
+  std::set<scoped_refptr<internal::TaskQueueImpl>> queues_to_delete_;
+
+  // This lock guards only |newly_updatable_|.  It's not expected to be heavily
+  // contended.
+  base::Lock newly_updatable_lock_;
+  std::vector<internal::TaskQueueImpl*> newly_updatable_;
+
+  // Set of task queues with avaliable work on the incoming queue.  This should
+  // only be accessed from the main thread.
+  std::set<internal::TaskQueueImpl*> updatable_queue_set_;
+
+  typedef std::multimap<base::TimeTicks, internal::TaskQueueImpl*>
+      DelayedWakeupMultimap;
+
+  DelayedWakeupMultimap delayed_wakeup_map_;
+
+  base::AtomicSequenceNumber task_sequence_num_;
+  base::debug::TaskAnnotator task_annotator_;
+
+  base::ThreadChecker main_thread_checker_;
+  scoped_refptr<NestableSingleThreadTaskRunner> main_task_runner_;
+  internal::TaskQueueSelector selector_;
+
+  base::Closure do_work_from_main_thread_closure_;
+  base::Closure do_work_from_other_thread_closure_;
+  base::Closure delayed_queue_wakeup_closure_;
+
+  bool task_was_run_on_quiescence_monitored_queue_;
+
+  // The pending_dowork_count_ is only tracked on the main thread since that's
+  // where re-entrant problems happen.
+  int pending_dowork_count_;
+
+  int work_batch_size_;
+
+  scoped_ptr<base::TickClock> time_source_;
+
+  base::ObserverList<base::MessageLoop::TaskObserver> task_observers_;
+
+  const char* disabled_by_default_tracing_category_;
+  const char* disabled_by_default_verbose_tracing_category_;
+
+  Observer* observer_;  // NOT OWNED
+  scoped_refptr<DeletionSentinel> deletion_sentinel_;
+  base::WeakPtrFactory<TaskQueueManager> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskQueueManager);
+};
+
+}  // namespace scheduler
+
+#endif  // CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_