get render threading working in melon

Squashed commit of the following:

commit 6c54b59f5f8f8bbf8698eebbc2a7e39079b0e726
Author: CasualPokePlayer <50538166+CasualPokePlayer@users.noreply.github.com>
Date:   Wed Mar 16 19:19:12 2022 -0700

    update submodule

commit 2c65d4375b64d8e729ebc0d35fd34865627bc494
Author: CasualPokePlayer <50538166+CasualPokePlayer@users.noreply.github.com>
Date:   Wed Mar 16 19:14:36 2022 -0700

    frontend stuff

commit 4566edcc623061beb6e3a7b2ead5571b42abdf3e
Author: CasualPokePlayer <50538166+CasualPokePlayer@users.noreply.github.com>
Date:   Wed Mar 16 18:10:45 2022 -0700

    probably hacky bullshit

commit 1fb9427c56a8d1af60378163cc2cafe6b36149c9
Author: CasualPokePlayer <50538166+CasualPokePlayer@users.noreply.github.com>
Date:   Wed Mar 16 00:59:58 2022 -0700

    more mt testing

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NDS/LibMelonDS.cs

@@ -132,10 +132,10 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 		public abstract IntPtr GetFrameThreadProc();
 
 		[UnmanagedFunctionPointer(CC)]
-		public delegate void ThreadWaitCallback();
+		public delegate void ThreadStartCallback();
 
 		[BizImport(CC)]
-		public abstract void SetThreadWaitCallback(ThreadWaitCallback callback);
+		public abstract void SetThreadStartCallback(ThreadStartCallback callback);
 
 		[BizImport(CC)]
 		public abstract int GetNANDSize();

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NDS/MelonDS.ISettable.cs

@@ -32,7 +32,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 
 		public class NDSSettings
 		{
-#if false
+#if true
 			[DisplayName("Threaded Rendering")]
 			[Description("")]
 			[DefaultValue(true)]

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NDS/MelonDS.cs

@@ -54,7 +54,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 
 			InitMemoryCallbacks();
 			_tracecb = MakeTrace;
-			_threadwaitcb = ThreadWaitCallback;
+			_threadstartcb = ThreadStartCallback;
 
 			_core = PreInit<LibMelonDS>(new WaterboxOptions
 			{
@@ -66,7 +66,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 				MmapHeapSizeKB = 1024 * 1024,
 				SkipCoreConsistencyCheck = CoreComm.CorePreferences.HasFlag(CoreComm.CorePreferencesFlags.WaterboxCoreConsistencyCheck),
 				SkipMemoryConsistencyCheck = CoreComm.CorePreferences.HasFlag(CoreComm.CorePreferencesFlags.WaterboxMemoryConsistencyCheck),
-			}, new Delegate[] { _readcb, _writecb, _execcb, _tracecb, _threadwaitcb });
+			}, new Delegate[] { _readcb, _writecb, _execcb, _tracecb, _threadstartcb });
 
 			var bios7 = IsDSi || _syncSettings.UseRealBIOS
 				? CoreComm.CoreFileProvider.GetFirmwareOrThrow(new("NDS", "bios7"))
@@ -112,7 +112,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 				loadFlags |= LibMelonDS.LoadFlags.IS_DSI;
 			if (IsDSi && IsDSiWare)
 				loadFlags |= LibMelonDS.LoadFlags.LOAD_DSIWARE;
-#if false
+#if true
 			if (_settings.ThreadedRendering)
 				loadFlags |= LibMelonDS.LoadFlags.THREADED_RENDERING;
 #endif
@@ -209,7 +209,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 			{
 				Console.WriteLine($"Setting up waterbox thread for 0x{_frameThreadPtr:X16}");
 				_frameThreadStart = CallingConventionAdapters.GetWaterboxUnsafeUnwrapped().GetDelegateForFunctionPointer<Action>(_frameThreadPtr);
-				_core.SetThreadWaitCallback(_threadwaitcb);
+				_core.SetThreadStartCallback(_threadstartcb);
 			}
 
 			_resampler = new SpeexResampler(SpeexResampler.Quality.QUALITY_DEFAULT, 32768, 44100, 32768, 44100, null, this);
@@ -327,16 +327,9 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 			return b;
 		}
 
-		private readonly IntPtr _frameThreadPtr;
-		private readonly Action _frameThreadStart;
-		private Task _frameThreadProcActive;
-
 		protected override LibWaterboxCore.FrameInfo FrameAdvancePrep(IController controller, bool render, bool rendersound)
 		{
-			if (_frameThreadStart != null && render)
+			_render = render;
-			{
-				_frameThreadProcActive = Task.Run(_frameThreadStart);
-			}
 			_core.SetTraceCallback(Tracer.IsEnabled() ? _tracecb : null);
 			return new LibMelonDS.FrameInfo
 			{
@@ -349,9 +342,26 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 			};
 		}
 
-		private readonly LibMelonDS.ThreadWaitCallback _threadwaitcb;
+		private readonly IntPtr _frameThreadPtr;
+		private readonly Action _frameThreadStart;
+		private readonly LibMelonDS.ThreadStartCallback _threadstartcb;
 
-		private void ThreadWaitCallback()
+		private bool _render;
+		private Task _frameThreadProcActive;
+
+		private void ThreadStartCallback()
+		{
+			if (_render)
+			{
+				if (_frameThreadProcActive != null)
+				{
+					throw new InvalidOperationException("Attempted to start render thread twice");
+				}
+				_frameThreadProcActive = Task.Run(_frameThreadStart);
+			}
+		}
+
+		protected override void FrameAdvancePost()
 		{
 			_frameThreadProcActive?.Wait();
 			_frameThreadProcActive = null;

waterbox/melon/BizInterface.cpp

@@ -72,7 +72,6 @@ typedef struct
 } FirmwareSettings;
 
 extern std::stringstream* NANDFilePtr;
-extern bool Stopped;
 
 static bool LoadDSiWare(u8* TmdData)
 {
@@ -154,7 +153,6 @@ EXPORT bool Init(LoadFlags loadFlags, LoadData* loadData, FirmwareSettings* fwSe
 	}
 	if (biz_skip_fw) NDS::SetupDirectBoot("");
 	NDS::Start();
-	Stopped = false;
 	Config::FirmwareOverrideSettings = false;
 	return true;
 }
@@ -374,7 +372,6 @@ EXPORT void FrameAdvance(MyFrameInfo* f)
 		NDS::LoadBIOS();
 		if (biz_skip_fw) NDS::SetupDirectBoot("");
 		NDS::Start();
-		Stopped = false;
 	}
 
 	NDS::SetKeyMask(~f->Keys & 0xFFF);
@@ -477,7 +474,7 @@ EXPORT void SetTraceCallback(void (*callback)(u32 cpu, u32* regs, u32 opcode))
 namespace Platform
 {
 	extern uintptr_t FrameThreadProc;
-	extern void (*ThreadWaitCallback)();
+	extern void (*ThreadStartCallback)();
 }
 
 EXPORT uintptr_t GetFrameThreadProc()
@@ -485,9 +482,9 @@ EXPORT uintptr_t GetFrameThreadProc()
 	return Platform::FrameThreadProc;
 }
 
-EXPORT void SetThreadWaitCallback(void (*callback)())
+EXPORT void SetThreadStartCallback(void (*callback)())
 {
-	Platform::ThreadWaitCallback = callback;
+	Platform::ThreadStartCallback = callback;
 }
 
 EXPORT u32 GetNANDSize()

waterbox/melon/BizPlatform.cpp

@@ -7,7 +7,6 @@
 
 bool NdsSaveRamIsDirty = false;
 std::stringstream* NANDFilePtr = NULL;
-bool Stopped = true;
 
 namespace Platform
 {
@@ -22,7 +21,6 @@ void DeInit()
 
 void StopEmu()
 {
-	Stopped = true;
 }
 
 int GetConfigInt(ConfigEntry entry)
@@ -163,11 +161,11 @@ FILE* OpenLocalFile(std::string path, std::string mode)
 
 uintptr_t FrameThreadProc = 0;
 std::function<void()> ThreadEntryFunc = nullptr;
-void (*ThreadWaitCallback)() = nullptr;
+void (*ThreadStartCallback)() = nullptr;
 
 void ThreadEntry()
 {
-	if (!Stopped) ThreadEntryFunc();
+	ThreadEntryFunc();
 }
 
 Thread* Thread_Create(std::function<void()> func)
@@ -181,44 +179,30 @@ void Thread_Free(Thread* thread)
 {
 }
 
-void Thread_Wait(Thread* thread)
+void Thread_Wait(Thread* thread) // hijacked to act as a thread start, consider this "wait for start of thread"
 {
-	ThreadWaitCallback();
+	ThreadStartCallback();
 }
 
 Semaphore* Semaphore_Create()
 {
-	int* s = new int;
+	return nullptr;
-	*s = 0;
-	return (Semaphore*)s;
 }
 
 void Semaphore_Free(Semaphore* sema)
 {
-	abort();
 }
 
 void Semaphore_Reset(Semaphore* sema)
 {
-	__atomic_store_n((int*)sema, 0, __ATOMIC_RELAXED);
 }
 
 void Semaphore_Wait(Semaphore* sema)
 {
-	int res;
-loop:
-	res = __atomic_load_n((int*)sema, __ATOMIC_RELAXED);
-	if (!res) goto loop;
-	__atomic_sub_fetch((int*)sema, 1, __ATOMIC_RELAXED);
-	if (__atomic_load_n((int*)sema, __ATOMIC_RELAXED) < 0)
-	{
-		__atomic_store_n((int*)sema, 0, __ATOMIC_RELAXED);
-	}
 }
 
 void Semaphore_Post(Semaphore* sema, int count)
 {
-	__atomic_add_fetch((int*)sema, (int)count, __ATOMIC_RELAXED);
 }
 
 Mutex* Mutex_Create()

waterbox/melon/melonDS

@@ -1 +1 @@
-Subproject commit 7e45e3582be653db468293189d63349c2632c3cb
+Subproject commit 69d0437b289d87d49c6ec68f81e454cf97c8e7d8