Fix AudioEntry destruction order. Add debugging CHECKs for racy shutdown.

media/audio/audio_output_controller.h

 // Copyright (c) 2012 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 MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 
 #include "base/atomic_ref_count.h"
 #include "base/callback.h"
 #include "base/cancelable_callback.h"
@@ skipping 197 matching lines @@
   // Calls EventHandler::OnPowerMeasured() with the current power level and then
   // schedules itself to be called again later.
   void ReportPowerMeasurementPeriodically();
 
   // Helper method that stops the physical stream.
   void StopStream();
 
   // Helper method that stops, closes, and NULLs |*stream_|.
   void DoStopCloseAndClearStream();
 
-  // Sanity-check that entry/exit to OnMoreIOData() by the hardware audio thread
-  // happens only between AudioOutputStream::Start() and Stop().
-  void AllowEntryToOnMoreIOData();
-  void DisallowEntryToOnMoreIOData();
-
   // Checks if a stream was started successfully but never calls OnMoreIOData().
   void WedgeCheck();
 
   AudioManager* const audio_manager_;
   const AudioParameters params_;
   EventHandler* const handler_;
 
   // Specifies the device id of the output device to open or empty for the
   // default output device.
   std::string output_device_id_;
 
   AudioOutputStream* stream_;
 
   // When non-NULL, audio is being diverted to this stream.
   AudioOutputStream* diverting_to_stream_;
 
   // The current volume of the audio stream.
   double volume_;
 
   // |state_| is written on the audio manager thread and is read on the
   // hardware audio thread. These operations need to be locked. But lock
   // is not required for reading on the audio manager thread.
   State state_;
 
-  // Binary semaphore, used to ensure that only one thread enters the
-  // OnMoreIOData() method, and only when it is valid to do so.  This is for
-  // sanity-checking the behavior of platform implementations of
-  // AudioOutputStream.  In other words, multiple contention is not expected,
-  // nor in the design here.
-  base::AtomicRefCount num_allowed_io_;
+  // Atomic ref count indicating when when we're in the middle of handling an
+  // OnMoreIOData() callback.  Will be CHECK'd to find crashes.
+  // TODO(dalecurtis): Remove debug helpers for http://crbug.com/349651
+  base::AtomicRefCount currently_in_on_more_io_data_;
 
   // SyncReader is used only in low latency mode for synchronous reading.
   SyncReader* const sync_reader_;
 
   // The message loop of audio manager thread that this object runs on.
   const scoped_refptr<base::SingleThreadTaskRunner> message_loop_;
 
 #if defined(AUDIO_POWER_MONITORING)
   // Scans audio samples from OnMoreIOData() as input to compute power levels.
   AudioPowerMonitor power_monitor_;
 
   // Periodic callback to report power levels during playback.
   base::CancelableClosure power_poll_callback_;
 #endif
 
   // Flags when we've asked for a stream to start but it never did.
   base::AtomicRefCount on_more_io_data_called_;
   scoped_ptr<base::OneShotTimer<AudioOutputController> > wedge_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_