TaskScheduler: Small improvements in SchedulerWorkerThread.

base/task_scheduler/scheduler_worker_thread.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_WORKER_THREAD_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_H_
 
 #include <memory>
 
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task_scheduler/scheduler_lock.h"
 #include "base/task_scheduler/sequence.h"
 #include "base/threading/platform_thread.h"
 
 namespace base {
 namespace internal {
 
 class SchedulerWorkerThreadDelegate;
 class TaskTracker;
 
 // A thread that runs Tasks from Sequences returned by a delegate.
 //
-// A SchedulerWorkerThread is woken up when its WakeUp() method is called. After
-// a wake-up, a SchedulerWorkerThread runs Tasks from Sequences returned by the
-// GetWork() method of its delegate as long as it doesn't return nullptr. It
-// also periodically checks with its TaskTracker whether shutdown has completed
-// and exits when it has.
+// A SchedulerWorkerThread starts out sleeping. It is woken up by a call to
+// WakeUp(). After a wake-up, a SchedulerWorkerThread runs Tasks from Sequences
+// returned by the GetWork() method of its delegate as long as it doesn't return
+// nullptr. It also periodically checks with its TaskTracker whether shutdown
+// has completed and exits when it has.
 //
 // This class is thread-safe.
 class BASE_EXPORT SchedulerWorkerThread : public PlatformThread::Delegate {
  public:
   // Creates a SchedulerWorkerThread with priority |thread_priority| that runs
   // Tasks from Sequences returned by |delegate|. |task_tracker| is used to
   // handle shutdown behavior of Tasks. Returns nullptr if creating the
   // underlying platform thread fails.
   static std::unique_ptr<SchedulerWorkerThread> CreateSchedulerWorkerThread(
       ThreadPriority thread_priority,
       SchedulerWorkerThreadDelegate* delegate,
       TaskTracker* task_tracker);
 
   // Destroying a SchedulerWorkerThread in production is not allowed; it is
   // always leaked. In tests, it can only be destroyed after JoinForTesting()
   // has returned.
   ~SchedulerWorkerThread() override;
 
-  // Wakes up this SchedulerWorkerThread. After this is called, this
-  // SchedulerWorkerThread will run Tasks from Sequences returned by the
-  // GetWork() method of its delegate until it returns nullptr.
+  // Wakes up this SchedulerWorkerThread if it wasn't already awake. After this
+  // is called, this SchedulerWorkerThread will run Tasks from Sequences
+  // returned by the GetWork() method of its delegate until it returns nullptr.
   void WakeUp();
 
   // Joins this SchedulerWorkerThread. If a Task is already running, it will be
   // allowed to complete its execution. This can only be called once.
   void JoinForTesting();
 
  private:
   SchedulerWorkerThread(ThreadPriority thread_priority,
                         SchedulerWorkerThreadDelegate* delegate,
                         TaskTracker* task_tracker);
@@ skipping 18 matching lines @@
   // True once JoinForTesting() has been called.
   bool should_exit_for_testing_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerThread);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_H_