| // 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 CC_RASTER_TASK_GRAPH_RUNNER_H_ |
| #define CC_RASTER_TASK_GRAPH_RUNNER_H_ |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| #include <algorithm> |
| #include <map> |
| #include <memory> |
| #include <vector> |
| |
| #include "base/logging.h" |
| #include "base/memory/ref_counted.h" |
| #include "cc/base/cc_export.h" |
| #include "cc/raster/task.h" |
| |
| namespace cc { |
| |
| // Opaque identifier that defines a namespace of tasks. |
| class CC_EXPORT NamespaceToken { |
| public: |
| NamespaceToken() : id_(0) {} |
| ~NamespaceToken() {} |
| |
| bool IsValid() const { return id_ != 0; } |
| |
| private: |
| friend class TaskGraphWorkQueue; |
| |
| explicit NamespaceToken(int id) : id_(id) {} |
| |
| int id_; |
| }; |
| |
| // A TaskGraphRunner is an object that runs a set of tasks in the |
| // order defined by a dependency graph. The TaskGraphRunner interface |
| // provides a way of decoupling task scheduling from the mechanics of |
| // how each task will be run. TaskGraphRunner provides the following |
| // guarantees: |
| // |
| // - Scheduled tasks will not run synchronously. That is, the |
| // ScheduleTasks() method will not call Task::Run() directly. |
| // |
| // - Scheduled tasks are guaranteed to run in the order defined by |
| // dependency graph. |
| // |
| // - Once scheduled, a task is guaranteed to end up in the |
| // |completed_tasks| vector populated by CollectCompletedTasks(), |
| // even if it later gets canceled by another call to ScheduleTasks(). |
| // |
| // TaskGraphRunner does not guarantee that a task with high priority |
| // runs after a task with low priority. The priority is just a hint |
| // and a valid TaskGraphRunner might ignore it. Also it does not |
| // guarantee a memory model for shared data between tasks. (In other |
| // words, you should use your own synchronization/locking primitives if |
| // you need to share data between tasks.) |
| // |
| // Implementations of TaskGraphRunner should be thread-safe in that all |
| // methods must be safe to call on any thread. |
| // |
| // Some theoretical implementations of TaskGraphRunner: |
| // |
| // - A TaskGraphRunner that uses a thread pool to run scheduled tasks. |
| // |
| // - A TaskGraphRunner that has a method Run() that runs each task. |
| class CC_EXPORT TaskGraphRunner { |
| public: |
| virtual ~TaskGraphRunner() {} |
| |
| // Returns a unique token that can be used to pass a task graph to |
| // ScheduleTasks(). Valid tokens are always nonzero. |
| virtual NamespaceToken GetNamespaceToken() = 0; |
| |
| // Schedule running of tasks in |graph|. Tasks previously scheduled but no |
| // longer needed will be canceled unless already running. Canceled tasks are |
| // moved to |completed_tasks| without being run. The result is that once |
| // scheduled, a task is guaranteed to end up in the |completed_tasks| queue |
| // even if it later gets canceled by another call to ScheduleTasks(). |
| virtual void ScheduleTasks(NamespaceToken token, TaskGraph* graph) = 0; |
| |
| // Wait for all scheduled tasks to finish running. |
| virtual void WaitForTasksToFinishRunning(NamespaceToken token) = 0; |
| |
| // Collect all completed tasks in |completed_tasks|. |
| virtual void CollectCompletedTasks(NamespaceToken token, |
| Task::Vector* completed_tasks) = 0; |
| }; |
| |
| } // namespace cc |
| |
| #endif // CC_RASTER_TASK_GRAPH_RUNNER_H_ |