made savestates synchronous and immediate. this allows saving or loading while the emulator is paused, fixes issues where savestate hotkeys would get ignored if pressed too close together, might speed up savestates in some cases, and hopefully makes savestates more stable too.

the intent is to replace the haphazard scheduling and finger-crossing associated with saving/loading with the correct and minimal necessary wait for each thread to reach a known safe location before commencing the savestate operation, and for any already-paused components to not need to be resumed to do so.

Source/Core/AudioCommon/Src/AudioCommon.cpp

@@ -118,4 +118,23 @@ namespace AudioCommon
 	bool UseJIT() {
 		return ac_Config.m_EnableJIT;
 	}
+
+	void PauseAndLock(bool doLock, bool unpauseOnUnlock)
+	{
+		if (soundStream)
+		{
+			// audio typically doesn't maintain its own "paused" state
+			// (that's already handled by the CPU and whatever else being paused)
+			// so it should be good enough to only lock/unlock here.
+			CMixer* pMixer = soundStream->GetMixer();
+			if (pMixer)
+			{
+				std::mutex& csMixing = pMixer->MixerCritical();
+				if (doLock)
+					csMixing.lock();
+				else
+					csMixing.unlock();
+			}
+		}
+	}
 }

Source/Core/AudioCommon/Src/AudioCommon.h

@@ -59,6 +59,7 @@ namespace AudioCommon
 	void ShutdownSoundStream();
 	std::vector<std::string> GetSoundBackends();
 	bool UseJIT();
+	void PauseAndLock(bool doLock, bool unpauseOnUnlock=true);
 }
 
 #endif // _AUDIO_COMMON_H_

Source/Core/AudioCommon/Src/Mixer.cpp

@@ -37,7 +37,9 @@ unsigned int CMixer::Mix(short* samples, unsigned int numSamples)
 	if (!samples)
 		return 0;
 
-	if (PowerPC::GetState() != 0)
+	std::lock_guard<std::mutex> lk(m_csMixing);
+
+	if (PowerPC::GetState() != PowerPC::CPU_RUNNING)
 	{
 		// Silence
 		memset(samples, 0, numSamples * 4);
@@ -164,7 +166,7 @@ void CMixer::PushSamples(const short *samples, unsigned int num_samples)
 		// The auto throttle function. This loop will put a ceiling on the CPU MHz.
 		while (num_samples + Common::AtomicLoad(m_numSamples) > MAX_SAMPLES)
 		{
-			if (*PowerPC::GetStatePtr() != 0) 
+			if (*PowerPC::GetStatePtr() != PowerPC::CPU_RUNNING || soundStream->IsMuted()) 
 				break;
 			// Shortcut key for Throttle Skipping
 			if (Host_GetKeyState('\t'))

Source/Core/AudioCommon/Src/Mixer.h

@@ -19,6 +19,7 @@
 #define _MIXER_H_
 
 #include "WaveFile.h"
+#include "StdMutex.h"
 
 // 16 bit Stereo
 #define MAX_SAMPLES			(1024 * 8)
@@ -89,6 +90,7 @@ public:
 		}
 	}
 
+	std::mutex& MixerCritical() { return m_csMixing; }
 
 protected:
 	unsigned int m_sampleRate;
@@ -110,7 +112,7 @@ protected:
 	u32 m_indexR;
 
 	bool m_AIplaying;
-
+	std::mutex m_csMixing;
 private:
 
 };

Source/Core/AudioCommon/Src/SoundStream.h

@@ -46,6 +46,7 @@ public:
 	virtual void Stop() {}
 	virtual void Update() {}
 	virtual void Clear(bool mute) { m_muted = mute; }
+	bool IsMuted() { return m_muted; }
 	virtual void StartLogAudio(const char *filename) {
 		if (! m_logAudio) {
 			m_logAudio = true;