Make threading lock-free

The core and the headless tools no longer use mutexes, condition variables,
spinlocks, std::atomic, std::thread or volatile flags. Threads hand off through
libretro-common's retro_atomic and rthreads plus a few small pieces on top of
them in Common/Thread: Thread, MpscQueue, EventCounter, ParkingLot waits and
ReaderGate. Every wait blocks until it's woken; nothing polls on a timer.

State that only one thread touches just loses its lock. The PSP filesystem,
sceIo and the savedata dialog now belong to the emulation thread: async reads
and writes run when they're queued and complete later in emulated time, and
the IO and savedata threads are gone. The friend finder only talks to the
adhoc server and hands what it gets to the emulation thread. GPU init always
runs on the thread that starts the game.

The Vulkan render and compile queues, pipeline and render pass caches, delete
list and SPIR-V cache, the GL render queue, the software renderer's jit caches,
the file loader caches, the web debugger, UPnP, input, savestates, logging and
the GE debugger all hand off through queues and atomics. The IR jit's spinning
profiler thread goes.

A CPU thread with nothing to run now sleeps until work is queued instead of
spinning. Headless with --debugger waits for a client while stopped, and ends
the run once every client that connected has left. Web server shutdown keeps
servicing the CPU queue until the server has finished.

Core/KeyMap.cpp

@@ -18,7 +18,6 @@
 #include <algorithm>
 #include <set>
 #include <unordered_map>
-#include <mutex>
 
 #include "ppsspp_config.h"
 
@@ -40,9 +39,7 @@
 
 namespace KeyMap {
 
-// We actually need to lock g_controllerMap since it can be modified! Crashes will probably be rare though,
-// but I've seen one. Let's just protect it with a mutex.
-std::recursive_mutex g_controllerMapLock;
+// Belongs to the thread that loads and saves the config.
 KeyMapping g_controllerMap;
 
 // Incremented on modification, so we know when to update menus.
@@ -601,7 +598,6 @@ const KeyMap::KeyMap_IntStrPair *GetMappableKeys(size_t *count) {
 
 bool InputMappingToPspButton(const InputMapping &mapping, std::vector<int> *pspButtons) {
 	bool found = false;
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	for (auto iter = g_controllerMap.begin(); iter != g_controllerMap.end(); ++iter) {
 		for (auto iter2 = iter->second.begin(); iter2 != iter->second.end(); ++iter2) {
 			if (iter2->EqualsSingleMapping(mapping)) {
@@ -614,19 +610,7 @@ bool InputMappingToPspButton(const InputMapping &mapping, std::vector<int> *pspB
 	return found;
 }
 
-void GetAllComboMappingsNoLock(std::vector<MultiInputMapping> *combos) {
-	combos->clear();
-	for (const auto &iter : g_controllerMap) {
-		for (const auto &mapping : iter.second) {
-			if (mapping.mappings.size() > 1) {
-				combos->push_back(mapping);
-			}
-		}
-	}
-}
-
-// This is the main workhorse of the ControlMapper.
-bool InputMappingsFromPspButtonNoLock(int btn, std::vector<MultiInputMapping> *mappings, bool ignoreMouse) {
+bool InputMappingsFromPspButton(int btn, std::vector<MultiInputMapping> *mappings, bool ignoreMouse) {
 	auto iter = g_controllerMap.find(btn);
 	if (iter == g_controllerMap.end()) {
 		return false;
@@ -647,21 +631,7 @@ bool InputMappingsFromPspButtonNoLock(int btn, std::vector<MultiInputMapping> *m
 	return mapped;
 }
 
-bool InputMappingsFromPspButton(int btn, std::vector<MultiInputMapping> *mappings, bool ignoreMouse) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
-	return InputMappingsFromPspButtonNoLock(btn, mappings, ignoreMouse);
-}
-
-void LockMappings() {
-	g_controllerMapLock.lock();
-}
-
-void UnlockMappings() {
-	g_controllerMapLock.unlock();
-}
-
 bool PspButtonHasMappings(int btn) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	auto iter = g_controllerMap.find(btn);
 	if (iter == g_controllerMap.end()) {
 		return false;
@@ -696,7 +666,6 @@ MappedAnalogAxes MappedAxesForDevice(InputDeviceID deviceId) {
 	};
 
 	MappedAnalogAxes result;
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	result.leftX = findAxisIdPair(VIRTKEY_AXIS_X_MIN, VIRTKEY_AXIS_X_MAX);
 	result.leftY = findAxisIdPair(VIRTKEY_AXIS_Y_MIN, VIRTKEY_AXIS_Y_MAX);
 	result.rightX = findAxisIdPair(VIRTKEY_AXIS_RIGHT_X_MIN, VIRTKEY_AXIS_RIGHT_X_MAX);
@@ -705,7 +674,6 @@ MappedAnalogAxes MappedAxesForDevice(InputDeviceID deviceId) {
 }
 
 void RemoveButtonMapping(int btn) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	for (auto iter = g_controllerMap.begin(); iter != g_controllerMap.end(); ++iter)	{
 		if (iter->first == btn) {
 			g_controllerMap.erase(iter);
@@ -715,7 +683,6 @@ void RemoveButtonMapping(int btn) {
 }
 
 bool IsKeyMapped(InputDeviceID device, int key) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	for (auto &iter : g_controllerMap) {
 		for (auto &mappedKey : iter.second) {
 			if (mappedKey.mappings.contains(InputMapping(device, key))) {
@@ -727,7 +694,6 @@ bool IsKeyMapped(InputDeviceID device, int key) {
 }
 
 bool ReplaceSingleKeyMapping(int btn, int index, const MultiInputMapping &key) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	// Check for duplicate
 	for (int i = 0; i < (int)g_controllerMap[btn].size(); ++i) {
 		if (i != index && g_controllerMap[btn][i] == key) {
@@ -754,7 +720,6 @@ bool ReplaceSingleKeyMapping(int btn, int index, const MultiInputMapping &key) {
 }
 
 void DeleteNthMapping(int key, int number) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	auto iter = g_controllerMap.find(key);
 	if (iter != g_controllerMap.end()) {
 		if (number < iter->second.size()) {
@@ -765,7 +730,6 @@ void DeleteNthMapping(int key, int number) {
 }
 
 void SetInputMapping(int btn, const MultiInputMapping &key, bool replace) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	if (key.empty()) {
 		g_controllerMap.erase(btn);
 		return;
@@ -789,7 +753,6 @@ void SetInputMapping(int btn, const MultiInputMapping &key, bool replace) {
 }
 
 void RestoreDefault() {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	g_controllerMap.clear();
 	g_controllerMapGeneration++;
 
@@ -833,7 +796,6 @@ void LoadFromIni(IniFile &file) {
 		return;
 	}
 
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 
 	Section *controls = file.GetOrCreateSection("ControlMapping");
 	for (size_t i = 0; i < ARRAY_SIZE(psp_button_names); i++) {
@@ -866,7 +828,6 @@ void LoadFromIni(IniFile &file) {
 void SaveToIni(IniFile &file) {
 	Section *controls = file.GetOrCreateSection("ControlMapping");
 
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 
 	for (size_t i = 0; i < ARRAY_SIZE(psp_button_names); i++) {
 		std::vector<MultiInputMapping> keys;
@@ -884,7 +845,6 @@ void SaveToIni(IniFile &file) {
 }
 
 void ClearAllMappings() {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	g_controllerMap.clear();
 	g_controllerMapGeneration++;
 }
@@ -917,7 +877,6 @@ bool HasBuiltinController(std::string_view name) {
 
 void NotifyPadConnected(InputDeviceID deviceId, std::string_view name) {
 	{
-		std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 		g_seenPads.insert(std::string(name));
 		g_padNames[deviceId] = name;
 
@@ -934,7 +893,6 @@ void NotifyPadConnected(InputDeviceID deviceId, std::string_view name) {
 
 void NotifyPadDisconnected(InputDeviceID deviceId) {
 	{
-		std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 		auto iter = g_padNames.find(deviceId);
 		if (iter != g_padNames.end()) {
 			auto co = GetI18NCategory(I18NCat::CONTROLS);
@@ -948,7 +906,6 @@ void NotifyPadDisconnected(InputDeviceID deviceId) {
 
 void ClearControlsWithDeviceId(InputDeviceID deviceId) {
 	bool modified = false;
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	for (auto iter = g_controllerMap.begin(); iter != g_controllerMap.end(); ++iter) {
 		auto &mappings = iter->second;
 		for (auto mapIter = mappings.begin(); mapIter != mappings.end(); ) {
@@ -974,7 +931,6 @@ void ClearControlsWithDeviceId(InputDeviceID deviceId) {
 }
 
 void AutoConfForPad(std::string_view name) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 
 	InputDeviceID deviceId = DEVICE_ID_PAD_0;
 	for (auto [padDeviceId, padName] : g_padNames) {
@@ -1015,12 +971,10 @@ void AutoConfForPad(std::string_view name) {
 }
 
 const std::set<std::string> &GetSeenPads() {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	return g_seenPads;
 }
 
 std::string PadName(InputDeviceID deviceId) {
-	std::lock_guard<std::recursive_mutex> guard(g_controllerMapLock);
 	auto it = g_padNames.find(deviceId);
 	if (it != g_padNames.end())
 		return it->second;