From 09a76193f5fa87bfacefd2ea15249338792aad1d Mon Sep 17 00:00:00 2001
From: henrika <henrika@webrtc.org>
Date: Wed, 23 Aug 2017 15:04:40 +0200
Subject: [PATCH] Resolves threading issues when audio is interrupted on iOS.
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Before this change we could crash in Debug when WebRTC audio was first
interrupted and then resumed again. The reason was that the new audio
stream stems from a new native I/O thread and that triggered thread
checkers. With this change, failing thread checkers are detached when
audio is interrupted to ensure that they don't fail when audio is restarted.

NOTRY=TRUE

Bug: webrtc:8126
Change-Id: Ib36ff6bc942477730aba60066f049ed0c43d3901
Reviewed-on: https://chromium-review.googlesource.com/628716
Commit-Queue: Henrik Andreasson <henrika@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19465}
---
 webrtc/modules/audio_device/audio_device_buffer.cc  | 6 ++++++
 webrtc/modules/audio_device/audio_device_buffer.h   | 6 ++++++
 webrtc/modules/audio_device/ios/audio_device_ios.mm | 9 +++++++++
 3 files changed, 21 insertions(+)

diff --git a/webrtc/modules/audio_device/audio_device_buffer.cc b/webrtc/modules/audio_device/audio_device_buffer.cc
index 8227d5b077..905c69681f 100644
--- a/webrtc/modules/audio_device/audio_device_buffer.cc
+++ b/webrtc/modules/audio_device/audio_device_buffer.cc
@@ -260,6 +260,12 @@ int32_t AudioDeviceBuffer::SetTypingStatus(bool typing_status) {
   return 0;
 }
 
+void AudioDeviceBuffer::NativeAudioInterrupted() {
+  RTC_DCHECK(main_thread_checker_.CalledOnValidThread());
+  playout_thread_checker_.DetachFromThread();
+  recording_thread_checker_.DetachFromThread();
+}
+
 uint32_t AudioDeviceBuffer::NewMicLevel() const {
   RTC_DCHECK_RUN_ON(&recording_thread_checker_);
   return new_mic_level_;
diff --git a/webrtc/modules/audio_device/audio_device_buffer.h b/webrtc/modules/audio_device/audio_device_buffer.h
index 04e1be8687..2a5a84b22f 100644
--- a/webrtc/modules/audio_device/audio_device_buffer.h
+++ b/webrtc/modules/audio_device/audio_device_buffer.h
@@ -118,6 +118,12 @@ class AudioDeviceBuffer {
 
   int32_t SetTypingStatus(bool typing_status);
 
+  // Called on iOS where the native audio layer can be interrupted by other
+  // audio applications. This method can then be used to reset internal
+  // states and detach thread checkers to allow for a new audio session where
+  // native callbacks may come from a new set of I/O threads.
+  void NativeAudioInterrupted();
+
  private:
   // Starts/stops periodic logging of audio stats.
   void StartPeriodicLogging();
diff --git a/webrtc/modules/audio_device/ios/audio_device_ios.mm b/webrtc/modules/audio_device/ios/audio_device_ios.mm
index 1d59aff467..fb2f65d339 100644
--- a/webrtc/modules/audio_device/ios/audio_device_ios.mm
+++ b/webrtc/modules/audio_device/ios/audio_device_ios.mm
@@ -554,6 +554,15 @@ void AudioDeviceIOS::HandleInterruptionBegin() {
     RTCLog(@"Stopping the audio unit due to interruption begin.");
     if (!audio_unit_->Stop()) {
       RTCLogError(@"Failed to stop the audio unit for interruption begin.");
+    } else {
+      // The audio unit has been stopped but will be restarted when the
+      // interruption ends in HandleInterruptionEnd(). It will result in audio
+      // callbacks from a new native I/O thread which means that we must detach
+      // thread checkers here to be prepared for an upcoming new audio stream.
+      io_thread_checker_.DetachFromThread();
+      // The audio device buffer must also be informed about the interrupted
+      // state so it can detach its thread checkers as well.
+      audio_device_buffer_->NativeAudioInterrupted();
     }
   }
   is_interrupted_ = true;