Fix T86728: Blender freezes when playhead is dragged in this .blend

Porting the deadlock bugfix in WASAPI from upstream Audaspace.

extern/audaspace/plugins/wasapi/WASAPIDevice.cpp

@@ -35,7 +35,11 @@ void WASAPIDevice::start()
 {
 	lock();
 
-	if(!m_playing)
+	// thread is still running, we can abort stopping it
+	if(m_stop)
+		m_stop = false;
+	// thread is not running, let's start it
+	else if(!m_playing)
 	{
 		if(m_thread.joinable())
 			m_thread.join();
@@ -53,20 +57,35 @@ void WASAPIDevice::updateStream()
 	UINT32 buffer_size;
 	data_t* buffer;
 
+	lock();
+
 	if(FAILED(m_audio_client->GetBufferSize(&buffer_size)))
+	{
+		m_playing = false;
+		m_stop = false;
+		unlock();
 		return;
+	}
 
 	IAudioRenderClient* render_client = nullptr;
 	const IID IID_IAudioRenderClient = __uuidof(IAudioRenderClient);
 
 	if(FAILED(m_audio_client->GetService(IID_IAudioRenderClient, reinterpret_cast<void**>(&render_client))))
+	{
+		m_playing = false;
+		m_stop = false;
+		unlock();
 		return;
+	}
 
 	UINT32 padding;
 
 	if(FAILED(m_audio_client->GetCurrentPadding(&padding)))
 	{
 		SafeRelease(&render_client);
+		m_playing = false;
+		m_stop = false;
+		unlock();
 		return;
 	}
 
@@ -75,31 +94,40 @@ void WASAPIDevice::updateStream()
 	if(FAILED(render_client->GetBuffer(length, &buffer)))
 	{
 		SafeRelease(&render_client);
+		m_playing = false;
+		m_stop = false;
+		unlock();
 		return;
 	}
 
-	lock();
-
 	mix((data_t*)buffer, length);
 
-	unlock();
-
 	if(FAILED(render_client->ReleaseBuffer(length, 0)))
 	{
 		SafeRelease(&render_client);
+		m_playing = false;
+		m_stop = false;
+		unlock();
 		return;
 	}
 
+	unlock();
+
 	m_audio_client->Start();
 
 	auto sleepDuration = std::chrono::milliseconds(buffer_size * 1000 / int(m_specs.rate) / 2);
 
 	for(;;)
 	{
+		lock();
+
 		if(FAILED(m_audio_client->GetCurrentPadding(&padding)))
 		{
 			m_audio_client->Stop();
 			SafeRelease(&render_client);
+			m_playing = false;
+			m_stop = false;
+			unlock();
 			return;
 		}
 
@@ -109,44 +137,52 @@ void WASAPIDevice::updateStream()
 		{
 			m_audio_client->Stop();
 			SafeRelease(&render_client);
+			m_playing = false;
+			m_stop = false;
+			unlock();
 			return;
 		}
 
-		lock();
-
 		mix((data_t*)buffer, length);
 
-		unlock();
-
 		if(FAILED(render_client->ReleaseBuffer(length, 0)))
 		{
 			m_audio_client->Stop();
 			SafeRelease(&render_client);
+			m_playing = false;
+			m_stop = false;
+			unlock();
 			return;
 		}
 
 		// stop thread
-		if(!m_playing)
+		if(m_stop)
 		{
 			m_audio_client->Stop();
 			SafeRelease(&render_client);
+			m_playing = false;
+			m_stop = false;
+			unlock();
 			return;
 		}
 
+		unlock();
+
 		std::this_thread::sleep_for(sleepDuration);
 	}
 }
 
 void WASAPIDevice::playing(bool playing)
 {
-	if(!m_playing && playing)
+	if((!m_playing || m_stop) && playing)
 		start();
 	else
-		m_playing = playing;
+		m_stop = true;
 }
 
 WASAPIDevice::WASAPIDevice(DeviceSpecs specs, int buffersize) :
 	m_playing(false),
+	m_stop(false),
 
 	m_imm_device_enumerator(nullptr),
 	m_imm_device(nullptr),

extern/audaspace/plugins/wasapi/WASAPIDevice.h

@@ -48,6 +48,11 @@ private:
 	 */
 	bool m_playing;
 
+	/**
+	 * Whether the current playback should stop.
+	 */
+	bool m_stop;
+
 	IMMDeviceEnumerator* m_imm_device_enumerator;
 	IMMDevice* m_imm_device;
 	IAudioClient* m_audio_client;