diff --git a/modules/audio_device/mac/audio_device_mac.cc b/modules/audio_device/mac/audio_device_mac.cc
index e894cf309a..9368c31263 100644
--- a/modules/audio_device/mac/audio_device_mac.cc
+++ b/modules/audio_device/mac/audio_device_mac.cc
@@ -410,7 +410,10 @@ int32_t AudioDeviceMac::SpeakerIsAvailable(bool& available) {
 
 int32_t AudioDeviceMac::InitSpeaker() {
   rtc::CritScope lock(&_critSect);
+  return InitSpeakerLocked();
+}
 
+int32_t AudioDeviceMac::InitSpeakerLocked() {
   if (_playing) {
     return -1;
   }
@@ -458,7 +461,10 @@ int32_t AudioDeviceMac::MicrophoneIsAvailable(bool& available) {
 
 int32_t AudioDeviceMac::InitMicrophone() {
   rtc::CritScope lock(&_critSect);
+  return InitMicrophoneLocked();
+}
 
+int32_t AudioDeviceMac::InitMicrophoneLocked() {
   if (_recording) {
     return -1;
   }
@@ -960,7 +966,7 @@ int32_t AudioDeviceMac::InitPlayout() {
   }
 
   // Initialize the speaker (devices might have been added or removed)
-  if (InitSpeaker() == -1) {
+  if (InitSpeakerLocked() == -1) {
     RTC_LOG(LS_WARNING) << "InitSpeaker() failed";
   }
 
@@ -1098,7 +1104,7 @@ int32_t AudioDeviceMac::InitRecording() {
   }
 
   // Initialize the microphone (devices might have been added or removed)
-  if (InitMicrophone() == -1) {
+  if (InitMicrophoneLocked() == -1) {
     RTC_LOG(LS_WARNING) << "InitMicrophone() failed";
   }
 
diff --git a/modules/audio_device/mac/audio_device_mac.h b/modules/audio_device/mac/audio_device_mac.h
index d7076a3c1c..8d0e7fa571 100644
--- a/modules/audio_device/mac/audio_device_mac.h
+++ b/modules/audio_device/mac/audio_device_mac.h
@@ -69,8 +69,8 @@ class AudioDeviceMac : public AudioDeviceGeneric {
       AudioDeviceModule::AudioLayer& audioLayer) const;
 
   // Main initializaton and termination
-  virtual InitStatus Init();
-  virtual int32_t Terminate();
+  virtual InitStatus Init() RTC_LOCKS_EXCLUDED(_critSect);
+  virtual int32_t Terminate() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool Initialized() const;
 
   // Device enumeration
@@ -84,7 +84,8 @@ class AudioDeviceMac : public AudioDeviceGeneric {
                                       char guid[kAdmMaxGuidSize]);
 
   // Device selection
-  virtual int32_t SetPlayoutDevice(uint16_t index);
+  virtual int32_t SetPlayoutDevice(uint16_t index)
+      RTC_LOCKS_EXCLUDED(_critSect);
   virtual int32_t SetPlayoutDevice(AudioDeviceModule::WindowsDeviceType device);
   virtual int32_t SetRecordingDevice(uint16_t index);
   virtual int32_t SetRecordingDevice(
@@ -92,24 +93,24 @@ class AudioDeviceMac : public AudioDeviceGeneric {
 
   // Audio transport initialization
   virtual int32_t PlayoutIsAvailable(bool& available);
-  virtual int32_t InitPlayout();
+  virtual int32_t InitPlayout() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool PlayoutIsInitialized() const;
   virtual int32_t RecordingIsAvailable(bool& available);
-  virtual int32_t InitRecording();
+  virtual int32_t InitRecording() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool RecordingIsInitialized() const;
 
   // Audio transport control
-  virtual int32_t StartPlayout();
-  virtual int32_t StopPlayout();
+  virtual int32_t StartPlayout() RTC_LOCKS_EXCLUDED(_critSect);
+  virtual int32_t StopPlayout() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool Playing() const;
-  virtual int32_t StartRecording();
-  virtual int32_t StopRecording();
+  virtual int32_t StartRecording() RTC_LOCKS_EXCLUDED(_critSect);
+  virtual int32_t StopRecording() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool Recording() const;
 
   // Audio mixer initialization
-  virtual int32_t InitSpeaker();
+  virtual int32_t InitSpeaker() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool SpeakerIsInitialized() const;
-  virtual int32_t InitMicrophone();
+  virtual int32_t InitMicrophone() RTC_LOCKS_EXCLUDED(_critSect);
   virtual bool MicrophoneIsInitialized() const;
 
   // Speaker volume controls
@@ -147,9 +148,13 @@ class AudioDeviceMac : public AudioDeviceGeneric {
   // Delay information and control
   virtual int32_t PlayoutDelay(uint16_t& delayMS) const;
 
-  virtual void AttachAudioBuffer(AudioDeviceBuffer* audioBuffer);
+  virtual void AttachAudioBuffer(AudioDeviceBuffer* audioBuffer)
+      RTC_LOCKS_EXCLUDED(_critSect);
 
  private:
+  int32_t InitSpeakerLocked() RTC_EXCLUSIVE_LOCKS_REQUIRED(_critSect);
+  int32_t InitMicrophoneLocked() RTC_EXCLUSIVE_LOCKS_REQUIRED(_critSect);
+
   virtual int32_t MicrophoneIsAvailable(bool& available);
   virtual int32_t SpeakerIsAvailable(bool& available);
 
@@ -229,13 +234,15 @@ class AudioDeviceMac : public AudioDeviceGeneric {
   OSStatus implDeviceIOProc(const AudioBufferList* inputData,
                             const AudioTimeStamp* inputTime,
                             AudioBufferList* outputData,
-                            const AudioTimeStamp* outputTime);
+                            const AudioTimeStamp* outputTime)
+      RTC_LOCKS_EXCLUDED(_critSect);
 
   OSStatus implOutConverterProc(UInt32* numberDataPackets,
                                 AudioBufferList* data);
 
   OSStatus implInDeviceIOProc(const AudioBufferList* inputData,
-                              const AudioTimeStamp* inputTime);
+                              const AudioTimeStamp* inputTime)
+      RTC_LOCKS_EXCLUDED(_critSect);
 
   OSStatus implInConverterProc(UInt32* numberDataPackets,
                                AudioBufferList* data);
diff --git a/modules/audio_device/mac/audio_mixer_manager_mac.cc b/modules/audio_device/mac/audio_mixer_manager_mac.cc
index e2b7d6370d..b34b5c3422 100644
--- a/modules/audio_device/mac/audio_mixer_manager_mac.cc
+++ b/modules/audio_device/mac/audio_mixer_manager_mac.cc
@@ -63,16 +63,19 @@ int32_t AudioMixerManagerMac::Close() {
 
   rtc::CritScope lock(&_critSect);
 
-  CloseSpeaker();
-  CloseMicrophone();
+  CloseSpeakerLocked();
+  CloseMicrophoneLocked();
 
   return 0;
 }
 
 int32_t AudioMixerManagerMac::CloseSpeaker() {
-  RTC_LOG(LS_VERBOSE) << __FUNCTION__;
-
   rtc::CritScope lock(&_critSect);
+  return CloseSpeakerLocked();
+}
+
+int32_t AudioMixerManagerMac::CloseSpeakerLocked() {
+  RTC_LOG(LS_VERBOSE) << __FUNCTION__;
 
   _outputDeviceID = kAudioObjectUnknown;
   _noOutputChannels = 0;
@@ -81,9 +84,12 @@ int32_t AudioMixerManagerMac::CloseSpeaker() {
 }
 
 int32_t AudioMixerManagerMac::CloseMicrophone() {
-  RTC_LOG(LS_VERBOSE) << __FUNCTION__;
-
   rtc::CritScope lock(&_critSect);
+  return CloseMicrophoneLocked();
+}
+
+int32_t AudioMixerManagerMac::CloseMicrophoneLocked() {
+  RTC_LOG(LS_VERBOSE) << __FUNCTION__;
 
   _inputDeviceID = kAudioObjectUnknown;
   _noInputChannels = 0;
diff --git a/modules/audio_device/mac/audio_mixer_manager_mac.h b/modules/audio_device/mac/audio_mixer_manager_mac.h
index 342e1c997c..ee6149d672 100644
--- a/modules/audio_device/mac/audio_mixer_manager_mac.h
+++ b/modules/audio_device/mac/audio_mixer_manager_mac.h
@@ -21,29 +21,29 @@ namespace webrtc {
 
 class AudioMixerManagerMac {
  public:
-  int32_t OpenSpeaker(AudioDeviceID deviceID);
-  int32_t OpenMicrophone(AudioDeviceID deviceID);
-  int32_t SetSpeakerVolume(uint32_t volume);
+  int32_t OpenSpeaker(AudioDeviceID deviceID) RTC_LOCKS_EXCLUDED(_critSect);
+  int32_t OpenMicrophone(AudioDeviceID deviceID) RTC_LOCKS_EXCLUDED(_critSect);
+  int32_t SetSpeakerVolume(uint32_t volume) RTC_LOCKS_EXCLUDED(_critSect);
   int32_t SpeakerVolume(uint32_t& volume) const;
   int32_t MaxSpeakerVolume(uint32_t& maxVolume) const;
   int32_t MinSpeakerVolume(uint32_t& minVolume) const;
   int32_t SpeakerVolumeIsAvailable(bool& available);
   int32_t SpeakerMuteIsAvailable(bool& available);
-  int32_t SetSpeakerMute(bool enable);
+  int32_t SetSpeakerMute(bool enable) RTC_LOCKS_EXCLUDED(_critSect);
   int32_t SpeakerMute(bool& enabled) const;
   int32_t StereoPlayoutIsAvailable(bool& available);
   int32_t StereoRecordingIsAvailable(bool& available);
   int32_t MicrophoneMuteIsAvailable(bool& available);
-  int32_t SetMicrophoneMute(bool enable);
+  int32_t SetMicrophoneMute(bool enable) RTC_LOCKS_EXCLUDED(_critSect);
   int32_t MicrophoneMute(bool& enabled) const;
   int32_t MicrophoneVolumeIsAvailable(bool& available);
-  int32_t SetMicrophoneVolume(uint32_t volume);
+  int32_t SetMicrophoneVolume(uint32_t volume) RTC_LOCKS_EXCLUDED(_critSect);
   int32_t MicrophoneVolume(uint32_t& volume) const;
   int32_t MaxMicrophoneVolume(uint32_t& maxVolume) const;
   int32_t MinMicrophoneVolume(uint32_t& minVolume) const;
-  int32_t Close();
-  int32_t CloseSpeaker();
-  int32_t CloseMicrophone();
+  int32_t Close() RTC_LOCKS_EXCLUDED(_critSect);
+  int32_t CloseSpeaker() RTC_LOCKS_EXCLUDED(_critSect);
+  int32_t CloseMicrophone() RTC_LOCKS_EXCLUDED(_critSect);
   bool SpeakerIsInitialized() const;
   bool MicrophoneIsInitialized() const;
 
@@ -52,6 +52,8 @@ class AudioMixerManagerMac {
   ~AudioMixerManagerMac();
 
  private:
+  int32_t CloseSpeakerLocked() RTC_EXCLUSIVE_LOCKS_REQUIRED(_critSect);
+  int32_t CloseMicrophoneLocked() RTC_EXCLUSIVE_LOCKS_REQUIRED(_critSect);
   static void logCAMsg(const rtc::LoggingSeverity sev,
                        const char* msg,
                        const char* err);