coreinit: Dont yield uninterruptible threads in spinlock

src/Cafe/OS/libs/coreinit/coreinit_Spinlock.cpp

@@ -128,11 +128,25 @@ namespace coreinit
 		else
 		{
 			// loop until lock acquired
+			if (coreinit::__CemuIsMulticoreMode())
+			{
+				while (!spinlock->ownerThread.atomic_compare_exchange(nullptr, currentThread))
+				{
+					_mm_pause();
+				}
+			}
+			else
+			{
+				// we are in single-core mode and the lock will never be released unless we let other threads resume work
+				// to avoid an infinite loop we have no choice but to yield the thread even it is in an uninterruptible state
+				if( !OSIsInterruptEnabled() )
+					cemuLog_log(LogType::APIErrors, "OSUninterruptibleSpinLock_Acquire(): Lock is occupied which requires a wait but current thread is already in an uninterruptible state (Avoid cascaded OSDisableInterrupts and/or OSUninterruptibleSpinLock)");
 				while (!spinlock->ownerThread.atomic_compare_exchange(nullptr, currentThread))
 				{
 					OSYieldThread();
 				}
 			}
+		}
 		__OSBoostThread(currentThread);
 		spinlock->interruptMask = OSDisableInterrupts();
 		cemu_assert_debug(spinlock->ownerThread == currentThread);

src/Cafe/OS/libs/coreinit/coreinit_Thread.cpp

@@ -66,6 +66,11 @@ namespace coreinit
 
 	std::unordered_map<OSThread_t*, OSHostThread*> s_threadToFiber;
 
+	bool __CemuIsMulticoreMode()
+	{
+		return g_isMulticoreMode;
+	}
+
 	// create host thread (fiber) that will be used to run the PPC instance
 	// note that host threads are fibers and not actual threads
 	void __OSCreateHostThread(OSThread_t* thread)

src/Cafe/OS/libs/coreinit/coreinit_Thread.h

@@ -488,6 +488,8 @@ namespace coreinit
 	void InitializeThread();
 	void InitializeConcurrency();
 
+	bool __CemuIsMulticoreMode();
+
 	OSThread_t* OSGetDefaultThread(sint32 coreIndex);
 	void* OSGetDefaultThreadStack(sint32 coreIndex, uint32& size);