content/child/worker_task_runner.h

   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 #ifndef CONTENT_CHILD_WORKER_TASK_RUNNER_H_
   6 #define CONTENT_CHILD_WORKER_TASK_RUNNER_H_
   7
   8 #include <map>
   9
  10 #include "base/callback_forward.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "base/synchronization/lock.h"
  13 #include "base/threading/platform_thread.h"
  14 #include "base/threading/thread_local.h"
  15 #include "content/common/content_export.h"
  16
  17 namespace base {
  18 class TaskRunner;
  19 }
  20
  21 namespace content {
  22
  23 class CONTENT_EXPORT WorkerTaskRunner {
  24  public:
  25   WorkerTaskRunner();
  26
  27   bool PostTask(int id, const base::Closure& task);
  28   int PostTaskToAllThreads(const base::Closure& task);
  29   int CurrentWorkerId();
  30   static WorkerTaskRunner* Instance();
  31
  32   class CONTENT_EXPORT Observer {
  33    public:
  34     virtual ~Observer() {}
  35     virtual void OnWorkerRunLoopStopped() = 0;
  36   };
  37   // Add/Remove an observer that will get notified when the current worker run
  38   // loop is stopping. This observer will not get notified when other threads
  39   // are stopping.  It's only valid to call these on a worker thread.
  40   void AddStopObserver(Observer* observer);
  41   void RemoveStopObserver(Observer* observer);
  42
  43   void OnWorkerRunLoopStarted();
  44   void OnWorkerRunLoopStopped();
  45
  46   base::TaskRunner* GetTaskRunnerFor(int worker_id);
  47
  48  private:
  49   friend class WorkerTaskRunnerTest;
  50
  51   using IDToTaskRunnerMap = std::map<base::PlatformThreadId, base::TaskRunner*>;
  52
  53   ~WorkerTaskRunner();
  54
  55   // It is possible for an IPC message to arrive for a worker thread that has
  56   // already gone away. In such cases, it is still necessary to provide a
  57   // task-runner for that particular thread, because otherwise the message will
  58   // end up being handled as per usual in the main-thread, causing incorrect
  59   // results. |task_runner_for_dead_worker_| is used to handle such messages,
  60   // which silently discards all the tasks it receives.
  61   scoped_refptr<base::TaskRunner> task_runner_for_dead_worker_;
  62
  63   struct ThreadLocalState;
  64   base::ThreadLocalPointer<ThreadLocalState> current_tls_;
  65
  66   IDToTaskRunnerMap task_runner_map_;
  67   base::Lock task_runner_map_lock_;
  68 };
  69
  70 }  // namespace content
  71
  72 #endif  // CONTENT_CHILD_WORKER_TASK_RUNNER_H_