base/threading/worker_pool.cc

   1 // Copyright (c) 2012 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/threading/worker_pool.h"
   6
   7 #include "base/bind.h"
   8 #include "base/compiler_specific.h"
   9 #include "base/lazy_instance.h"
  10 #include "base/task_runner.h"
  11 #include "base/threading/post_task_and_reply_impl.h"
  12 #include "base/tracked_objects.h"
  13
  14 namespace base {
  15
  16 namespace {
  17
  18 class PostTaskAndReplyWorkerPool : public internal::PostTaskAndReplyImpl {
  19  public:
  20   PostTaskAndReplyWorkerPool(bool task_is_slow) : task_is_slow_(task_is_slow) {
  21   }
  22
  23  private:
  24   virtual bool PostTask(const tracked_objects::Location& from_here,
  25                         const Closure& task) OVERRIDE {
  26     return WorkerPool::PostTask(from_here, task, task_is_slow_);
  27   }
  28
  29   bool task_is_slow_;
  30 };
  31
  32 // WorkerPoolTaskRunner ---------------------------------------------
  33 // A TaskRunner which posts tasks to a WorkerPool with a
  34 // fixed ShutdownBehavior.
  35 //
  36 // Note that this class is RefCountedThreadSafe (inherited from TaskRunner).
  37 class WorkerPoolTaskRunner : public TaskRunner {
  38  public:
  39   WorkerPoolTaskRunner(bool tasks_are_slow);
  40
  41   // TaskRunner implementation
  42   virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
  43                                const Closure& task,
  44                                TimeDelta delay) OVERRIDE;
  45   virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
  46
  47  private:
  48   virtual ~WorkerPoolTaskRunner();
  49
  50   // Helper function for posting a delayed task. Asserts that the delay is
  51   // zero because non-zero delays are not supported.
  52   bool PostDelayedTaskAssertZeroDelay(
  53       const tracked_objects::Location& from_here,
  54       const Closure& task,
  55       base::TimeDelta delay);
  56
  57   const bool tasks_are_slow_;
  58
  59   DISALLOW_COPY_AND_ASSIGN(WorkerPoolTaskRunner);
  60 };
  61
  62 WorkerPoolTaskRunner::WorkerPoolTaskRunner(bool tasks_are_slow)
  63     : tasks_are_slow_(tasks_are_slow) {
  64 }
  65
  66 WorkerPoolTaskRunner::~WorkerPoolTaskRunner() {
  67 }
  68
  69 bool WorkerPoolTaskRunner::PostDelayedTask(
  70     const tracked_objects::Location& from_here,
  71     const Closure& task,
  72     TimeDelta delay) {
  73   return PostDelayedTaskAssertZeroDelay(from_here, task, delay);
  74 }
  75
  76 bool WorkerPoolTaskRunner::RunsTasksOnCurrentThread() const {
  77   return WorkerPool::RunsTasksOnCurrentThread();
  78 }
  79
  80 bool WorkerPoolTaskRunner::PostDelayedTaskAssertZeroDelay(
  81     const tracked_objects::Location& from_here,
  82     const Closure& task,
  83     base::TimeDelta delay) {
  84   DCHECK_EQ(delay.InMillisecondsRoundedUp(), 0)
  85       << "WorkerPoolTaskRunner does not support non-zero delays";
  86   return WorkerPool::PostTask(from_here, task, tasks_are_slow_);
  87 }
  88
  89 struct TaskRunnerHolder {
  90   TaskRunnerHolder() {
  91     taskrunners_[0] = new WorkerPoolTaskRunner(false);
  92     taskrunners_[1] = new WorkerPoolTaskRunner(true);
  93   }
  94   scoped_refptr<TaskRunner> taskrunners_[2];
  95 };
  96
  97 base::LazyInstance<TaskRunnerHolder>::Leaky
  98     g_taskrunners = LAZY_INSTANCE_INITIALIZER;
  99
 100 }  // namespace
 101
 102 bool WorkerPool::PostTaskAndReply(const tracked_objects::Location& from_here,
 103                                   const Closure& task,
 104                                   const Closure& reply,
 105                                   bool task_is_slow) {
 106   return PostTaskAndReplyWorkerPool(task_is_slow).PostTaskAndReply(
 107       from_here, task, reply);
 108 }
 109
 110 // static
 111 const scoped_refptr<TaskRunner>&
 112 WorkerPool::GetTaskRunner(bool tasks_are_slow) {
 113   return g_taskrunners.Get().taskrunners_[tasks_are_slow];
 114 }
 115
 116 }  // namespace base