Improved error handling in iOS ADM to avoid race during init

webrtc/modules/audio_device/ios/audio_device_ios.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_DEVICE_IOS_AUDIO_DEVICE_IOS_H_
 #define WEBRTC_MODULES_AUDIO_DEVICE_IOS_AUDIO_DEVICE_IOS_H_
 
 #include <AudioUnit/AudioUnit.h>
 
+#include "webrtc/base/criticalsection.h"
 #include "webrtc/base/scoped_ptr.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/audio_device/audio_device_generic.h"
 
 namespace webrtc {
 
 class FineAudioBuffer;
 
 // Implements full duplex 16-bit mono PCM audio support for iOS using a
 // Voice-Processing (VP) I/O audio unit in Core Audio. The VP I/O audio unit
@@ skipping 151 matching lines @@
   // a BT headset is enabled or disabled.
   bool RestartAudioUnitWithNewFormat(float sample_rate);
 
   // Activates our audio session, creates and initializes the voice-processing
   // audio unit and verifies that we got the preferred native audio parameters.
   bool InitPlayOrRecord();
 
   // Closes and deletes the voice-processing I/O unit.
   bool ShutdownPlayOrRecord();
 
+  // Helper method for destroying the existing audio unit.
+  void DisposeAudioUnit();
+
   // Callback function called on a real-time priority I/O thread from the audio
   // unit. This method is used to signal that recorded audio is available.
   static OSStatus RecordedDataIsAvailable(
       void* in_ref_con,
       AudioUnitRenderActionFlags* io_action_flags,
       const AudioTimeStamp* time_stamp,
       UInt32 in_bus_number,
       UInt32 in_number_frames,
       AudioBufferList* io_data);
   OSStatus OnRecordedDataIsAvailable(
       AudioUnitRenderActionFlags* io_action_flags,
       const AudioTimeStamp* time_stamp,
       UInt32 in_bus_number,
       UInt32 in_number_frames);
 
   // Callback function called on a real-time priority I/O thread from the audio
   // unit. This method is used to provide audio samples to the audio unit.
   static OSStatus GetPlayoutData(void* in_ref_con,
                                  AudioUnitRenderActionFlags* io_action_flags,
                                  const AudioTimeStamp* time_stamp,
                                  UInt32 in_bus_number,
                                  UInt32 in_number_frames,
                                  AudioBufferList* io_data);
   OSStatus OnGetPlayoutData(AudioUnitRenderActionFlags* io_action_flags,
                             UInt32 in_number_frames,
                             AudioBufferList* io_data);
 
+  // Counts number of times setActive:YES has been called on the singleton
+  // AVAudioSession instance. Used to ensure that we don't disable an audio
+  // session when it is still in used by other instances of this object.
+  // Member is static to ensure that the value is counted for all instances
+  // and not per instance.
+  static int audio_session_activation_count_;

[pbos-webrtc, 2015/11/18 12:54:22]

Put GUARDED_BY(lock_) between "count_" and ";"

[henrika_webrtc, 2015/11/18 16:05:32]

Done.

+
+  // Protects |audio_session_activation_count_|.
+  static rtc::GlobalLockPod lock_;
+
   // Ensures that methods are called from the same thread as this object is
   // created on.
   rtc::ThreadChecker thread_checker_;
 
   // Raw pointer handle provided to us in AttachAudioBuffer(). Owned by the
   // AudioDeviceModuleImpl class and called by AudioDeviceModuleImpl::Create().
   // The AudioDeviceBuffer is a member of the AudioDeviceModuleImpl instance
   // and therefore outlives this object.
   AudioDeviceBuffer* audio_device_buffer_;
 
@@ skipping 62 matching lines @@
   void* audio_interruption_observer_;
   void* route_change_observer_;
 
   // Contains the audio data format specification for a stream of audio.
   AudioStreamBasicDescription application_format_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_DEVICE_IOS_AUDIO_DEVICE_IOS_H_