scheduler: Add a base directory

components/scheduler/child/task_queue.h

-// Copyright 2015 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 COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_
-#define COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_
-
-#include "base/message_loop/message_loop.h"
-#include "base/single_thread_task_runner.h"
-#include "components/scheduler/scheduler_export.h"
-
-namespace scheduler {
-
-class SCHEDULER_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
- public:
-  TaskQueue() {}
-
-  // Unregisters the task queue after which no tasks posted to it will run and
-  // the TaskQueueManager's reference to it will be released soon.
-  virtual void UnregisterTaskQueue() = 0;
-
-  // Post a delayed task at an absolute desired run time instead of a time
-  // delta from the current time.
-  virtual bool PostDelayedTaskAt(const tracked_objects::Location& from_here,
-                                 const base::Closure& task,
-                                 base::TimeTicks desired_run_time) = 0;
-
-  enum QueuePriority {
-    // Queues with control priority will run before any other queue, and will
-    // explicitly starve other queues. Typically this should only be used for
-    // private queues which perform control operations.
-    CONTROL_PRIORITY,
-    // Queues with high priority will be selected preferentially over normal or
-    // best effort queues. The selector will ensure that high priority queues
-    // cannot completely starve normal priority queues.
-    HIGH_PRIORITY,
-    // Queues with normal priority are the default.
-    NORMAL_PRIORITY,
-    // Queues with best effort priority will only be run if all other queues are
-    // empty. They can be starved by the other queues.
-    BEST_EFFORT_PRIORITY,
-    // Queues with this priority are never run.  Must be penultimate entry.
-    DISABLED_PRIORITY,
-    // Must be the last entry.
-    QUEUE_PRIORITY_COUNT,
-    FIRST_QUEUE_PRIORITY = CONTROL_PRIORITY,
-  };
-
-  // Keep TaskQueue::PumpPolicyToString in sync with this enum.
-  enum class PumpPolicy {
-    // Tasks posted to an incoming queue with an AUTO pump policy will be
-    // automatically scheduled for execution or transferred to the work queue
-    // automatically.
-    AUTO,
-    // Tasks posted to an incoming queue with an AFTER_WAKEUP pump policy
-    // will be scheduled for execution or transferred to the work queue
-    // automatically but only after another queue has executed a task.
-    AFTER_WAKEUP,
-    // Tasks posted to an incoming queue with a MANUAL will not be
-    // automatically scheduled for execution or transferred to the work queue.
-    // Instead, the selector should call PumpQueue() when necessary to bring
-    // in new tasks for execution.
-    MANUAL,
-    // Must be last entry.
-    PUMP_POLICY_COUNT,
-    FIRST_PUMP_POLICY = AUTO,
-  };
-
-  // Keep TaskQueue::WakeupPolicyToString in sync with this enum.
-  enum class WakeupPolicy {
-    // Tasks run on a queue with CAN_WAKE_OTHER_QUEUES wakeup policy can
-    // cause queues with the AFTER_WAKEUP PumpPolicy to be woken up.
-    CAN_WAKE_OTHER_QUEUES,
-    // Tasks run on a queue with DONT_WAKE_OTHER_QUEUES won't cause queues
-    // with the AFTER_WAKEUP PumpPolicy to be woken up.
-    DONT_WAKE_OTHER_QUEUES,
-    // Must be last entry.
-    WAKEUP_POLICY_COUNT,
-    FIRST_WAKEUP_POLICY = CAN_WAKE_OTHER_QUEUES,
-  };
-
-  enum class QueueState {
-    // A queue in the EMPTY state is empty and has no tasks in either the
-    // work or incoming task queue.
-    EMPTY,
-    // A queue in the NEEDS_PUMPING state has no tasks in the work task queue,
-    // but has tasks in the incoming task queue which can be pumped to make them
-    // runnable.
-    NEEDS_PUMPING,
-    // A queue in the HAS_WORK state has tasks in the work task queue which
-    // are runnable.
-    HAS_WORK,
-  };
-
-  // Options for constructing a TaskQueue. Once set the |name|,
-  // |should_monitor_quiescence| and |wakeup_policy| are immutable. The
-  // |pump_policy| can be mutated with |SetPumpPolicy()|.
-  struct Spec {
-    // Note |name| must have application lifetime.
-    explicit Spec(const char* name)
-        : name(name),
-          should_monitor_quiescence(false),
-          pump_policy(TaskQueue::PumpPolicy::AUTO),
-          wakeup_policy(TaskQueue::WakeupPolicy::CAN_WAKE_OTHER_QUEUES),
-          should_notify_observers(true) {}
-
-    Spec SetShouldMonitorQuiescence(bool should_monitor) {
-      should_monitor_quiescence = should_monitor;
-      return *this;
-    }
-
-    Spec SetPumpPolicy(PumpPolicy policy) {
-      pump_policy = policy;
-      return *this;
-    }
-
-    Spec SetWakeupPolicy(WakeupPolicy policy) {
-      wakeup_policy = policy;
-      return *this;
-    }
-
-    Spec SetShouldNotifyObservers(bool run_observers) {
-      should_notify_observers = run_observers;
-      return *this;
-    }
-
-    const char* name;
-    bool should_monitor_quiescence;
-    TaskQueue::PumpPolicy pump_policy;
-    TaskQueue::WakeupPolicy wakeup_policy;
-    bool should_notify_observers;
-  };
-
-  // Returns true if the queue priority is not
-  // TaskQueueSelector::DISABLED_PRIORITY. NOTE this must be called on the
-  // thread this TaskQueue was created by.
-  virtual bool IsQueueEnabled() const = 0;
-
-  // Returns true if there no tasks in either the work or incoming task queue.
-  // Note that this function involves taking a lock, so calling it has some
-  // overhead. NOTE this must be called on the thread this TaskQueue was created
-  // by.
-  virtual bool IsQueueEmpty() const;
-
-  // Returns the QueueState. Note that this function involves taking a lock, so
-  // calling it has some overhead.
-  virtual QueueState GetQueueState() const = 0;
-
-  // Can be called on any thread.
-  virtual const char* GetName() const = 0;
-
-  // Set the priority of the queue to |priority|. NOTE this must be called on
-  // the thread this TaskQueue was created by.
-  virtual void SetQueuePriority(QueuePriority priority) = 0;
-
-  // Set the pumping policy of the queue to |pump_policy|. NOTE this must be
-  // called on the thread this TaskQueue was created by.
-  virtual void SetPumpPolicy(PumpPolicy pump_policy) = 0;
-
-  // Reloads new tasks from the incoming queue into the work queue, regardless
-  // of whether the work queue is empty or not. After this, the function ensures
-  // that the tasks in the work queue, if any, are scheduled for execution.
-  //
-  // This function only needs to be called if automatic pumping is disabled.
-  // By default automatic pumping is enabled for all queues. NOTE this must be
-  // called on the thread this TaskQueue was created by.
-  virtual void PumpQueue() = 0;
-
-  // These functions can only be called on the same thread that the task queue
-  // manager executes its tasks on.
-  virtual void AddTaskObserver(
-      base::MessageLoop::TaskObserver* task_observer) = 0;
-  virtual void RemoveTaskObserver(
-      base::MessageLoop::TaskObserver* task_observer) = 0;
-
- protected:
-  ~TaskQueue() override {}
-
-  DISALLOW_COPY_AND_ASSIGN(TaskQueue);
-};
-
-}  // namespace scheduler
-
-#endif  // COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_