Home | History | Annotate | Download | only in task_scheduler 
      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 #include "base/task_scheduler/task.h"
      6 
      7 #include <utility>
      8 
      9 #include "base/atomic_sequence_num.h"
     10 #include "base/critical_closure.h"
     11 
     12 namespace base {
     13 namespace internal {
     14 
     15 namespace {
     16 
     17 AtomicSequenceNumber g_sequence_nums_for_tracing;
     18 
     19 }  // namespace
     20 
     21 Task::Task(const Location& posted_from,
     22            OnceClosure task,
     23            const TaskTraits& traits,
     24            TimeDelta delay)
     25     : PendingTask(
     26           posted_from,
     27           traits.shutdown_behavior() == TaskShutdownBehavior::BLOCK_SHUTDOWN
     28               ? MakeCriticalClosure(std::move(task))
     29               : std::move(task),
     30           delay.is_zero() ? TimeTicks() : TimeTicks::Now() + delay,
     31           Nestable::kNonNestable),
     32       // Prevent a delayed BLOCK_SHUTDOWN task from blocking shutdown before it
     33       // starts running by changing its shutdown behavior to SKIP_ON_SHUTDOWN.
     34       traits(
     35           (!delay.is_zero() &&
     36            traits.shutdown_behavior() == TaskShutdownBehavior::BLOCK_SHUTDOWN)
     37               ? TaskTraits::Override(traits,
     38                                      {TaskShutdownBehavior::SKIP_ON_SHUTDOWN})
     39               : traits),
     40       delay(delay) {
     41   // TaskScheduler doesn't use |sequence_num| but tracing (toplevel.flow) relies
     42   // on it being unique. While this subtle dependency is a bit overreaching,
     43   // TaskScheduler is the only task system that doesn't use |sequence_num| and
     44   // the dependent code rarely changes so this isn't worth a big change and
     45   // faking it here isn't too bad for now (posting tasks is full of atomic ops
     46   // already).
     47   this->sequence_num = g_sequence_nums_for_tracing.GetNext();
     48 }
     49 
     50 // This should be "= default but MSVC has trouble with "noexcept = default" in
     51 // this case.
     52 Task::Task(Task&& other) noexcept
     53     : PendingTask(std::move(other)),
     54       traits(other.traits),
     55       delay(other.delay),
     56       sequenced_time(other.sequenced_time),
     57       sequenced_task_runner_ref(std::move(other.sequenced_task_runner_ref)),
     58       single_thread_task_runner_ref(
     59           std::move(other.single_thread_task_runner_ref)) {}
     60 
     61 Task::~Task() = default;
     62 
     63 Task& Task::operator=(Task&& other) = default;
     64 
     65 }  // namespace internal
     66 }  // namespace base
     67