1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_TASK_SCHEDULER_TASK_H_ 6 #define BASE_TASK_SCHEDULER_TASK_H_ 7 8 #include "base/base_export.h" 9 #include "base/callback.h" 10 #include "base/location.h" 11 #include "base/macros.h" 12 #include "base/memory/ref_counted.h" 13 #include "base/pending_task.h" 14 #include "base/sequenced_task_runner.h" 15 #include "base/single_thread_task_runner.h" 16 #include "base/task_scheduler/task_traits.h" 17 #include "base/time/time.h" 18 19 namespace base { 20 namespace internal { 21 22 // A task is a unit of work inside the task scheduler. Support for tracing and 23 // profiling inherited from PendingTask. 24 struct BASE_EXPORT Task : public PendingTask { 25 // |posted_from| is the site the task was posted from. |task| is the closure 26 // to run. |traits_in| is metadata about the task. |delay| is a delay that 27 // must expire before the Task runs. If |delay| is non-zero and the shutdown 28 // behavior in |traits| is BLOCK_SHUTDOWN, the shutdown behavior is 29 // automatically adjusted to SKIP_ON_SHUTDOWN. 30 Task(const Location& posted_from, 31 OnceClosure task, 32 const TaskTraits& traits, 33 TimeDelta delay); 34 35 // Task is move-only to avoid mistakes that cause reference counts to be 36 // accidentally bumped. 37 Task(Task&& other) noexcept; 38 39 ~Task(); 40 41 Task& operator=(Task&& other); 42 43 // The TaskTraits of this task. 44 TaskTraits traits; 45 46 // The delay that must expire before the task runs. 47 TimeDelta delay; 48 49 // The time at which the task was inserted in its sequence. For an undelayed 50 // task, this happens at post time. For a delayed task, this happens some 51 // time after the task's delay has expired. If the task hasn't been inserted 52 // in a sequence yet, this defaults to a null TimeTicks. 53 TimeTicks sequenced_time; 54 55 // A reference to the SequencedTaskRunner or SingleThreadTaskRunner that 56 // posted this task, if any. Used to set ThreadTaskRunnerHandle and/or 57 // SequencedTaskRunnerHandle while the task is running. 58 // Note: this creates an ownership cycle 59 // Sequence -> Task -> TaskRunner -> Sequence -> ... 60 // but that's okay as it's broken when the Task is popped from its Sequence 61 // after being executed which means this cycle forces the TaskRunner to stick 62 // around until all its tasks have been executed which is a requirement to 63 // support TaskRunnerHandles. 64 scoped_refptr<SequencedTaskRunner> sequenced_task_runner_ref; 65 scoped_refptr<SingleThreadTaskRunner> single_thread_task_runner_ref; 66 67 private: 68 DISALLOW_COPY_AND_ASSIGN(Task); 69 }; 70 71 } // namespace internal 72 } // namespace base 73 74 #endif // BASE_TASK_SCHEDULER_TASK_H_ 75