1
    2
    3
    4
    5
    6
    7
    8
    9
   10
   11
   12
   13
   14
   15
   16
   17
   18
   19
   20
   21
   22
   23
   24
   25
   26
   27
   28
   29
   30
   31
   32
   33
   34
   35
   36
   37
   38
   39
   40
   41
   42
   43
   44
   45
   46
   47
   48
   49
   50
   51
   52
   53
   54
   55
   56
   57
   58
   59
   60
   61
   62
   63
   64
   65
   66
   67
   68
   69
   70
   71
   72
   73
   74
   75
   76
   77
   78
   79
   80
   81
   82
   83
   84
   85
   86
   87
   88
   89
   90
   91
   92
   93
   94
   95
   96
   97
   98
   99
  100
  101
  102
  103
  104
  105
  106
  107
  108
  109
  110
  111
  112
  113
  114
  115
  116
  117
  118
  119
  120
  121
  122
  123
  124
  125
  126
  127
  128
  129
  130
  131
  132
  133
  134
  135
  136
  137
  138
  139
  140
  141
  142
  143
  144
  145
  146
  147


base / task / deferred_sequenced_task_runner.cc [blame]

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/task/deferred_sequenced_task_runner.h"
#include "base/task/common/scoped_defer_task_posting.h"

#include <utility>

#include "base/check.h"
#include "base/functional/bind.h"

namespace base {

DeferredSequencedTaskRunner::DeferredTask::DeferredTask()
    : is_non_nestable(false) {
}

DeferredSequencedTaskRunner::DeferredTask::DeferredTask(DeferredTask&& other) =
    default;

DeferredSequencedTaskRunner::DeferredTask::~DeferredTask() = default;

DeferredSequencedTaskRunner::DeferredTask&
DeferredSequencedTaskRunner::DeferredTask::operator=(DeferredTask&& other) =
    default;

DeferredSequencedTaskRunner::DeferredSequencedTaskRunner(
    scoped_refptr<SequencedTaskRunner> target_task_runner)
    : created_thread_id_(PlatformThread::CurrentId()),
      target_task_runner_(std::move(target_task_runner)) {
#if DCHECK_IS_ON()
  AutoLock lock(lock_);
  DCHECK(target_task_runner_);
#endif
  task_runner_atomic_ptr_.store(target_task_runner_.get(),
                                std::memory_order_release);
}

DeferredSequencedTaskRunner::DeferredSequencedTaskRunner()
    : created_thread_id_(PlatformThread::CurrentId()) {}

bool DeferredSequencedTaskRunner::PostDelayedTask(const Location& from_here,
                                                  OnceClosure task,
                                                  TimeDelta delay) {
  // Do not process new PostTasks while we are handling a PostTask (tracing
  // has to do this) as it can lead to a deadlock and defer it instead.
  ScopedDeferTaskPosting disallow_task_posting;

  AutoLock lock(lock_);
  if (started_) {
    DCHECK(deferred_tasks_queue_.empty());
    return target_task_runner_->PostDelayedTask(from_here, std::move(task),
                                                delay);
  }

  QueueDeferredTask(from_here, std::move(task), delay,
                    false /* is_non_nestable */);
  return true;
}

bool DeferredSequencedTaskRunner::RunsTasksInCurrentSequence() const {
  // task_runner_atomic_ptr_ cannot change once it has been initialized, so it's
  // safe to access it without lock.
  SequencedTaskRunner* task_runner_ptr =
      task_runner_atomic_ptr_.load(std::memory_order_acquire);
  if (task_runner_ptr) {
    return task_runner_ptr->RunsTasksInCurrentSequence();
  }

  return created_thread_id_ == PlatformThread::CurrentId();
}

bool DeferredSequencedTaskRunner::PostNonNestableDelayedTask(
    const Location& from_here,
    OnceClosure task,
    TimeDelta delay) {
  AutoLock lock(lock_);
  if (started_) {
    DCHECK(deferred_tasks_queue_.empty());
    return target_task_runner_->PostNonNestableDelayedTask(
        from_here, std::move(task), delay);
  }
  QueueDeferredTask(from_here, std::move(task), delay,
                    true /* is_non_nestable */);
  return true;
}

void DeferredSequencedTaskRunner::Start() {
  AutoLock lock(lock_);
  StartImpl();
}

void DeferredSequencedTaskRunner::StartWithTaskRunner(
    scoped_refptr<SequencedTaskRunner> target_task_runner) {
  AutoLock lock(lock_);
  DCHECK(!target_task_runner_);
  DCHECK(target_task_runner);
  target_task_runner_ = std::move(target_task_runner);
  task_runner_atomic_ptr_.store(target_task_runner_.get(),
                                std::memory_order_release);
  StartImpl();
}

bool DeferredSequencedTaskRunner::Started() const {
  AutoLock lock(lock_);
  return started_;
}

DeferredSequencedTaskRunner::~DeferredSequencedTaskRunner() = default;

void DeferredSequencedTaskRunner::QueueDeferredTask(const Location& from_here,
                                                    OnceClosure task,
                                                    TimeDelta delay,
                                                    bool is_non_nestable) {
  lock_.AssertAcquired();

  // Use CHECK instead of DCHECK to crash earlier. See http://crbug.com/711167
  // for details.
  CHECK(task);

  DeferredTask deferred_task;
  deferred_task.posted_from = from_here;
  deferred_task.task = std::move(task);
  deferred_task.delay = delay;
  deferred_task.is_non_nestable = is_non_nestable;
  deferred_tasks_queue_.push_back(std::move(deferred_task));
}

void DeferredSequencedTaskRunner::StartImpl() {
  lock_.AssertAcquired();  // Callers should have grabbed the lock.
  DCHECK(!started_);
  started_ = true;
  DCHECK(target_task_runner_);
  for (auto& task : deferred_tasks_queue_) {
    if (task.is_non_nestable) {
      target_task_runner_->PostNonNestableDelayedTask(
          task.posted_from, std::move(task.task), task.delay);
    } else {
      target_task_runner_->PostDelayedTask(task.posted_from,
                                           std::move(task.task), task.delay);
    }
  }
  deferred_tasks_queue_.clear();
}

}  // namespace base