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      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/macros.h"
     11 #include "base/task_runner.h"
     12 #include "base/threading/post_task_and_reply_impl.h"
     13 #include "base/tracked_objects.h"
     14 
     15 namespace base {
     16 
     17 namespace {
     18 
     19 class PostTaskAndReplyWorkerPool : public internal::PostTaskAndReplyImpl {
     20  public:
     21   explicit PostTaskAndReplyWorkerPool(bool task_is_slow)
     22       : task_is_slow_(task_is_slow) {
     23   }
     24   ~PostTaskAndReplyWorkerPool() override = default;
     25 
     26  private:
     27   bool PostTask(const tracked_objects::Location& from_here,
     28                 const Closure& task) override {
     29     return WorkerPool::PostTask(from_here, task, task_is_slow_);
     30   }
     31 
     32   bool task_is_slow_;
     33 };
     34 
     35 // WorkerPoolTaskRunner ---------------------------------------------
     36 // A TaskRunner which posts tasks to a WorkerPool with a
     37 // fixed ShutdownBehavior.
     38 //
     39 // Note that this class is RefCountedThreadSafe (inherited from TaskRunner).
     40 class WorkerPoolTaskRunner : public TaskRunner {
     41  public:
     42   explicit WorkerPoolTaskRunner(bool tasks_are_slow);
     43 
     44   // TaskRunner implementation
     45   bool PostDelayedTask(const tracked_objects::Location& from_here,
     46                        const Closure& task,
     47                        TimeDelta delay) override;
     48   bool RunsTasksOnCurrentThread() const override;
     49 
     50  private:
     51   ~WorkerPoolTaskRunner() override;
     52 
     53   // Helper function for posting a delayed task. Asserts that the delay is
     54   // zero because non-zero delays are not supported.
     55   bool PostDelayedTaskAssertZeroDelay(
     56       const tracked_objects::Location& from_here,
     57       const Closure& task,
     58       base::TimeDelta delay);
     59 
     60   const bool tasks_are_slow_;
     61 
     62   DISALLOW_COPY_AND_ASSIGN(WorkerPoolTaskRunner);
     63 };
     64 
     65 WorkerPoolTaskRunner::WorkerPoolTaskRunner(bool tasks_are_slow)
     66     : tasks_are_slow_(tasks_are_slow) {
     67 }
     68 
     69 WorkerPoolTaskRunner::~WorkerPoolTaskRunner() {
     70 }
     71 
     72 bool WorkerPoolTaskRunner::PostDelayedTask(
     73     const tracked_objects::Location& from_here,
     74     const Closure& task,
     75     TimeDelta delay) {
     76   return PostDelayedTaskAssertZeroDelay(from_here, task, delay);
     77 }
     78 
     79 bool WorkerPoolTaskRunner::RunsTasksOnCurrentThread() const {
     80   return WorkerPool::RunsTasksOnCurrentThread();
     81 }
     82 
     83 bool WorkerPoolTaskRunner::PostDelayedTaskAssertZeroDelay(
     84     const tracked_objects::Location& from_here,
     85     const Closure& task,
     86     base::TimeDelta delay) {
     87   DCHECK_EQ(delay.InMillisecondsRoundedUp(), 0)
     88       << "WorkerPoolTaskRunner does not support non-zero delays";
     89   return WorkerPool::PostTask(from_here, task, tasks_are_slow_);
     90 }
     91 
     92 struct TaskRunnerHolder {
     93   TaskRunnerHolder() {
     94     taskrunners_[0] = new WorkerPoolTaskRunner(false);
     95     taskrunners_[1] = new WorkerPoolTaskRunner(true);
     96   }
     97   scoped_refptr<TaskRunner> taskrunners_[2];
     98 };
     99 
    100 base::LazyInstance<TaskRunnerHolder>::Leaky
    101     g_taskrunners = LAZY_INSTANCE_INITIALIZER;
    102 
    103 }  // namespace
    104 
    105 bool WorkerPool::PostTaskAndReply(const tracked_objects::Location& from_here,
    106                                   const Closure& task,
    107                                   const Closure& reply,
    108                                   bool task_is_slow) {
    109   // Do not report PostTaskAndReplyRelay leaks in tests. There's nothing we can
    110   // do about them because WorkerPool doesn't have a flushing API.
    111   // http://crbug.com/248513
    112   // http://crbug.com/290897
    113   return PostTaskAndReplyWorkerPool(task_is_slow).PostTaskAndReply(
    114       from_here, task, reply);
    115 }
    116 
    117 // static
    118 const scoped_refptr<TaskRunner>&
    119 WorkerPool::GetTaskRunner(bool tasks_are_slow) {
    120   return g_taskrunners.Get().taskrunners_[tasks_are_slow];
    121 }
    122 
    123 }  // namespace base
    124