Fixes for CTS multithread tests.

MTLDevice retains an internal object web that is used during the creation of
new objects, such as pipeline states, libraries, functions, and samplers.
Simultaneously creating and destroying objects of these types can trigger
race conditions on the internal MTLDevice content.

Wrap the following in @synchronized (mtlDevice) {...}:
- MTLRenderPipelineState creation and destruction
- MTLComputePipelineState creation and destruction
- MTLLibrary creation
- MTLFunction creation and specialization
- MTLSampler creation and destruction

MoltenVK/MoltenVK/GPUObjects/MVKImage.mm

@@ -1972,9 +1972,10 @@ MVKSampler::MVKSampler(MVKDevice* device, const VkSamplerCreateInfo* pCreateInfo
 	_requiresConstExprSampler = (pCreateInfo->compareEnable && !_device->_pMetalFeatures->depthSampleCompare) || _ycbcrConversion;
 
 	@autoreleasepool {
-		MTLSamplerDescriptor* mtlSampDesc = newMTLSamplerDescriptor(pCreateInfo);	// temp retain
+		auto mtlDev = getMTLDevice();
-		_mtlSamplerState = [getMTLDevice() newSamplerStateWithDescriptor: mtlSampDesc];
+		@synchronized (mtlDev) {
-		[mtlSampDesc release];														// temp release
+			_mtlSamplerState = [mtlDev newSamplerStateWithDescriptor: [newMTLSamplerDescriptor(pCreateInfo) autorelease]];
+		}
 	}
 
 	initConstExprSampler(pCreateInfo);
@@ -2060,5 +2061,7 @@ void MVKSampler::initConstExprSampler(const VkSamplerCreateInfo* pCreateInfo) {
 }
 
 MVKSampler::~MVKSampler() {
+	@synchronized (getMTLDevice()) {
 		[_mtlSamplerState release];
+	}
 }

MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm

@@ -1603,6 +1603,7 @@ bool MVKGraphicsPipeline::isRasterizationDisabled(const VkGraphicsPipelineCreate
 }
 
 MVKGraphicsPipeline::~MVKGraphicsPipeline() {
+	@synchronized (getMTLDevice()) {
 		[_mtlTessVertexStageDesc release];
 
 		[_mtlTessVertexStageState release];
@@ -1612,6 +1613,7 @@ MVKGraphicsPipeline::~MVKGraphicsPipeline() {
 		[_mtlPipelineState release];
 
 		for (id<MTLFunction> func : _mtlTessVertexFunctions) { [func release]; }
+	}
 }
 
 
@@ -1716,7 +1718,9 @@ MVKMTLFunction MVKComputePipeline::getMTLFunction(const VkComputePipelineCreateI
 }
 
 MVKComputePipeline::~MVKComputePipeline() {
+	@synchronized (getMTLDevice()) {
 		[_mtlPipelineState release];
+	}
 }
 
 
@@ -2147,11 +2151,14 @@ id<MTLRenderPipelineState> MVKRenderPipelineCompiler::newMTLRenderPipelineState(
 	unique_lock<mutex> lock(_completionLock);
 
 	compile(lock, ^{
-		[_owner->getMTLDevice() newRenderPipelineStateWithDescriptor: mtlRPLDesc
+		auto mtlDev = _owner->getMTLDevice();
+		@synchronized (mtlDev) {
+			[mtlDev newRenderPipelineStateWithDescriptor: mtlRPLDesc
 									   completionHandler: ^(id<MTLRenderPipelineState> ps, NSError* error) {
 				bool isLate = compileComplete(ps, error);
 				if (isLate) { destroy(); }
 			}];
+		}
 	});
 
 	return [_mtlRenderPipelineState retain];
@@ -2178,11 +2185,14 @@ id<MTLComputePipelineState> MVKComputePipelineCompiler::newMTLComputePipelineSta
 	unique_lock<mutex> lock(_completionLock);
 
 	compile(lock, ^{
-		[_owner->getMTLDevice() newComputePipelineStateWithFunction: mtlFunction
+		auto mtlDev = _owner->getMTLDevice();
+		@synchronized (mtlDev) {
+			[mtlDev newComputePipelineStateWithFunction: mtlFunction
 									  completionHandler: ^(id<MTLComputePipelineState> ps, NSError* error) {
 				bool isLate = compileComplete(ps, error);
 				if (isLate) { destroy(); }
 			}];
+		}
 	});
 
 	return [_mtlComputePipelineState retain];
@@ -2192,12 +2202,15 @@ id<MTLComputePipelineState> MVKComputePipelineCompiler::newMTLComputePipelineSta
 	unique_lock<mutex> lock(_completionLock);
 
 	compile(lock, ^{
-		[_owner->getMTLDevice() newComputePipelineStateWithDescriptor: plDesc
+		auto mtlDev = _owner->getMTLDevice();
+		@synchronized (mtlDev) {
+			[mtlDev newComputePipelineStateWithDescriptor: plDesc
 												  options: MTLPipelineOptionNone
 										completionHandler: ^(id<MTLComputePipelineState> ps, MTLComputePipelineReflection*, NSError* error) {
 				bool isLate = compileComplete(ps, error);
 				if (isLate) { destroy(); }
 			}];
+		}
 	});
 
 	return [_mtlComputePipelineState retain];

MoltenVK/MoltenVK/GPUObjects/MVKShaderModule.mm

@@ -62,7 +62,7 @@ MVKMTLFunction MVKShaderLibrary::getMTLFunction(const VkSpecializationInfo* pSpe
 
 	if ( !_mtlLibrary ) { return MVKMTLFunctionNull; }
 
-	@synchronized (_mtlLibrary) {
+	@synchronized (_owner->getMTLDevice()) {
 		@autoreleasepool {
 			NSString* mtlFuncName = @(_shaderConversionResults.entryPoint.mtlFunctionName.c_str());
 			MVKDevice* mvkDev = _owner->getDevice();
@@ -423,13 +423,16 @@ id<MTLLibrary> MVKShaderLibraryCompiler::newMTLLibrary(NSString* mslSourceCode,
 	unique_lock<mutex> lock(_completionLock);
 
 	compile(lock, ^{
-		[_owner->getMTLDevice() newLibraryWithSource: mslSourceCode
+		auto mtlDev = _owner->getMTLDevice();
+		@synchronized (mtlDev) {
+			[mtlDev newLibraryWithSource: mslSourceCode
 								 options: _owner->getDevice()->getMTLCompileOptions(shaderConversionResults.entryPoint.supportsFastMath,
 																					shaderConversionResults.isPositionInvariant)
 					   completionHandler: ^(id<MTLLibrary> mtlLib, NSError* error) {
 				bool isLate = compileComplete(mtlLib, error);
 				if (isLate) { destroy(); }
 			}];
+		}
 	});
 
 	return [_mtlLibrary retain];
@@ -467,12 +470,14 @@ id<MTLFunction> MVKFunctionSpecializer::newMTLFunction(id<MTLLibrary> mtlLibrary
 	unique_lock<mutex> lock(_completionLock);
 
 	compile(lock, ^{
+		@synchronized (_owner->getMTLDevice()) {
 			[mtlLibrary newFunctionWithName: funcName
 							 constantValues: constantValues
 						  completionHandler: ^(id<MTLFunction> mtlFunc, NSError* error) {
 				bool isLate = compileComplete(mtlFunc, error);
 				if (isLate) { destroy(); }
 			}];
+		}
 	});
 
 	return [_mtlFunction retain];