content/child/worker_task_runner.cc

   1 // Copyright 2014 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 "content/child/worker_task_runner.h"
   6
   7 #include "base/callback.h"
   8 #include "base/lazy_instance.h"
   9 #include "base/location.h"
  10 #include "base/logging.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/observer_list.h"
  13 #include "base/single_thread_task_runner.h"
  14 #include "base/stl_util.h"
  15 #include "base/thread_task_runner_handle.h"
  16
  17 namespace content {
  18
  19 namespace {
  20
  21 // A task-runner that refuses to run any tasks.
  22 class DoNothingTaskRunner : public base::TaskRunner {
  23  public:
  24   DoNothingTaskRunner() {}
  25
  26  private:
  27   ~DoNothingTaskRunner() override {}
  28
  29   bool PostDelayedTask(const tracked_objects::Location& from_here,
  30                        const base::Closure& task,
  31                        base::TimeDelta delay) override {
  32     return false;
  33   }
  34
  35   bool RunsTasksOnCurrentThread() const override { return false; }
  36 };
  37
  38 }  // namespace
  39
  40 struct WorkerTaskRunner::ThreadLocalState {
  41   ThreadLocalState() {}
  42   ObserverList<WorkerTaskRunner::Observer> stop_observers_;
  43 };
  44
  45 WorkerTaskRunner::WorkerTaskRunner()
  46     : task_runner_for_dead_worker_(new DoNothingTaskRunner()) {
  47 }
  48
  49 bool WorkerTaskRunner::PostTask(
  50     int id, const base::Closure& closure) {
  51   DCHECK(id > 0);
  52   base::AutoLock locker(task_runner_map_lock_);
  53   IDToTaskRunnerMap::iterator found = task_runner_map_.find(id);
  54   if (found == task_runner_map_.end())
  55     return false;
  56   return found->second->PostTask(FROM_HERE, closure);
  57 }
  58
  59 int WorkerTaskRunner::PostTaskToAllThreads(const base::Closure& closure) {
  60   base::AutoLock locker(task_runner_map_lock_);
  61   for (const auto& it : task_runner_map_)
  62     it.second->PostTask(FROM_HERE, closure);
  63   return static_cast<int>(task_runner_map_.size());
  64 }
  65
  66 int WorkerTaskRunner::CurrentWorkerId() {
  67   if (!current_tls_.Get())
  68     return 0;
  69   return base::PlatformThread::CurrentId();
  70 }
  71
  72 WorkerTaskRunner* WorkerTaskRunner::Instance() {
  73   static base::LazyInstance<WorkerTaskRunner>::Leaky
  74       worker_task_runner = LAZY_INSTANCE_INITIALIZER;
  75   return worker_task_runner.Pointer();
  76 }
  77
  78 void WorkerTaskRunner::AddStopObserver(Observer* obs) {
  79   DCHECK(CurrentWorkerId() > 0);
  80   current_tls_.Get()->stop_observers_.AddObserver(obs);
  81 }
  82
  83 void WorkerTaskRunner::RemoveStopObserver(Observer* obs) {
  84   DCHECK(CurrentWorkerId() > 0);
  85   current_tls_.Get()->stop_observers_.RemoveObserver(obs);
  86 }
  87
  88 WorkerTaskRunner::~WorkerTaskRunner() {
  89 }
  90
  91 void WorkerTaskRunner::OnWorkerRunLoopStarted() {
  92   DCHECK(!current_tls_.Get());
  93   DCHECK(!base::PlatformThread::CurrentRef().is_null());
  94   current_tls_.Set(new ThreadLocalState());
  95
  96   int id = base::PlatformThread::CurrentId();
  97   base::AutoLock locker_(task_runner_map_lock_);
  98   task_runner_map_[id] = base::ThreadTaskRunnerHandle::Get().get();
  99   CHECK(task_runner_map_[id]);
 100 }
 101
 102 void WorkerTaskRunner::OnWorkerRunLoopStopped() {
 103   DCHECK(current_tls_.Get());
 104   FOR_EACH_OBSERVER(Observer, current_tls_.Get()->stop_observers_,
 105                     OnWorkerRunLoopStopped());
 106   {
 107     base::AutoLock locker(task_runner_map_lock_);
 108     task_runner_map_.erase(CurrentWorkerId());
 109   }
 110   delete current_tls_.Get();
 111   current_tls_.Set(NULL);
 112 }
 113
 114 base::TaskRunner* WorkerTaskRunner::GetTaskRunnerFor(int worker_id) {
 115   base::AutoLock locker(task_runner_map_lock_);
 116   return ContainsKey(task_runner_map_, worker_id) ? task_runner_map_[worker_id]
 117                                            : task_runner_for_dead_worker_.get();
 118 }
 119
 120 }  // namespace content