TaskScheduler [11] Support ExecutionMode::SINGLE_THREADED.

base/task_scheduler/scheduler_thread_pool_impl.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_IMPL_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
+#include <unordered_map>

[robliao, 2016/04/27 17:43:45]

Nit: Remove?

[fdoray, 2016/04/27 19:17:04]

Done.

 #include <vector>
 
 #include "base/base_export.h"
 #include "base/callback.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/task_runner.h"
 #include "base/task_scheduler/priority_queue.h"
 #include "base/task_scheduler/scheduler_lock.h"
 #include "base/task_scheduler/scheduler_thread_pool.h"
 #include "base/task_scheduler/scheduler_worker_thread.h"
 #include "base/task_scheduler/scheduler_worker_thread_stack.h"
 #include "base/task_scheduler/sequence.h"
@@ skipping 40 matching lines @@
   // allowed to complete their execution. This can only be called once.
   void JoinForTesting();
 
   // SchedulerThreadPool:
   scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
       const TaskTraits& traits,
       ExecutionMode execution_mode) override;
   void ReEnqueueSequence(scoped_refptr<Sequence> sequence,
                          const SequenceSortKey& sequence_sort_key) override;
   bool PostTaskWithSequence(std::unique_ptr<Task> task,
-                            scoped_refptr<Sequence> sequence) override;
+                            scoped_refptr<Sequence> sequence,
+                            SchedulerWorkerThread* worker_thread) override;
   void PostTaskWithSequenceNow(std::unique_ptr<Task> task,
-                               scoped_refptr<Sequence> sequence) override;
+                               scoped_refptr<Sequence> sequence,
+                               SchedulerWorkerThread* worker_thread) override;
 
  private:
   class SchedulerWorkerThreadDelegateImpl;
 
-  SchedulerThreadPoolImpl(
-      TaskTracker* task_tracker,
-      DelayedTaskManager* delayed_task_manager);
+  SchedulerThreadPoolImpl(TaskTracker* task_tracker,
+                          DelayedTaskManager* delayed_task_manager);
 
   bool Initialize(
       ThreadPriority thread_priority,
       size_t max_threads,
       const ReEnqueueSequenceCallback& re_enqueue_sequence_callback);
 
   // Wakes up the last thread from this thread pool to go idle, if any.
   void WakeUpOneThread();
 
   // Adds |worker_thread| to |idle_worker_threads_stack_|.
   void AddToIdleWorkerThreadsStack(SchedulerWorkerThread* worker_thread);
 
-  // PriorityQueue from which all threads of this thread pool get work.
-  PriorityQueue shared_priority_queue_;
+  // Removes |worker_thread| from |idle_worker_threads_stack_|.
+  void RemoveFromIdleWorkerThreadsStack(SchedulerWorkerThread* worker_thread);
 
   // All worker threads owned by this thread pool. Only modified during
   // initialization of the thread pool.
   std::vector<std::unique_ptr<SchedulerWorkerThread>> worker_threads_;
 
+  // Synchronizes access to |next_worker_thread_index_|.
+  SchedulerLock next_worker_thread_index_lock_;
+
+  // Index of the worker thread that will be assigned to the next single-
+  // threaded TaskRunner returned by this pool.
+  size_t next_worker_thread_index_ = 0;
+
+  // PriorityQueue from which all threads of this thread pool get work.
+  PriorityQueue shared_priority_queue_;
+
   // Synchronizes access to |idle_worker_threads_stack_| and
   // |idle_worker_threads_stack_cv_for_testing_|. Has |shared_priority_queue_|'s
   // lock as its predecessor so that a thread can be pushed to
   // |idle_worker_threads_stack_| within the scope of a Transaction (more
   // details in GetWork()).
   SchedulerLock idle_worker_threads_stack_lock_;
 
   // Stack of idle worker threads.
   SchedulerWorkerThreadStack idle_worker_threads_stack_;
 
   // Signaled when all worker threads become idle.
   std::unique_ptr<ConditionVariable> idle_worker_threads_stack_cv_for_testing_;
 
   // Signaled once JoinForTesting() has returned.
   WaitableEvent join_for_testing_returned_;
 
+#if DCHECK_IS_ON()
+  // Signaled when all threads have been created.

[robliao, 2016/04/27 17:43:45]

Worth commented why we only care about this when DCHECK_IS_ON (Worker thread
check)

[gab, 2016/04/27 18:11:43]

I think the use of DCHECK_IS_ON() is self-documenting as "only needed for
DCHECKs" and the exact reason can easily be searched for it in impl if one
really wants to know.

[fdoray, 2016/04/27 19:17:04]

Didn't do anything about this.

+  WaitableEvent threads_created_;
+#endif  // DCHECK_IS_ON()
+
   TaskTracker* const task_tracker_;
   DelayedTaskManager* const delayed_task_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerThreadPoolImpl);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_IMPL_H_