Move from dependency on JNI and Implement AtomicMutex

This commit is the start of moving towards a lockless and faster kernel which can run multiple independent threads with fast userspace synchronization.

app/src/main/cpp/main.cpp

@@ -5,8 +5,9 @@
 #include <csignal>
 
 bool Halt;
+jobject Surface;
 uint FaultCount;
-std::mutex jniMtx;
+skyline::Mutex jniMtx;
 
 void signalHandler(int signal) {
     syslog(LOG_ERR, "Halting program due to signal: %s", strsignal(signal));
@@ -54,10 +55,19 @@ extern "C" JNIEXPORT void Java_emu_skyline_GameActivity_executeRom(JNIEnv *env,
     logger->Info("Done in: {} ms", (std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()));
 }
 
-extern "C" JNIEXPORT void Java_emu_skyline_GameActivity_lockMutex(JNIEnv *env, jobject instance) {
+extern "C" JNIEXPORT void Java_emu_skyline_GameActivity_setHalt(JNIEnv *env, jobject instance, jboolean halt) {
     jniMtx.lock();
-}
-
-extern "C" JNIEXPORT void Java_emu_skyline_GameActivity_unlockMutex(JNIEnv *env, jobject instance) {
+    Halt = halt;
+    jniMtx.unlock();
+}
+
+extern "C" JNIEXPORT void Java_emu_skyline_GameActivity_setSurface(JNIEnv *env, jobject instance, jobject surface) {
+    jniMtx.lock();
+    if(!env->IsSameObject(Surface, nullptr))
+        env->DeleteGlobalRef(Surface);
+    if(!env->IsSameObject(surface, nullptr))
+        Surface = env->NewGlobalRef(surface);
+    else
+        Surface = surface;
     jniMtx.unlock();
 }

app/src/main/cpp/skyline/common.cpp

@@ -4,6 +4,21 @@
 #include <tinyxml2.h>
 
 namespace skyline {
+    void Mutex::lock() {
+        while (flag.exchange(true, std::memory_order_relaxed));
+        std::atomic_thread_fence(std::memory_order_acquire);
+    }
+
+    void Mutex::unlock() {
+        std::atomic_thread_fence(std::memory_order_release);
+        flag.store(false, std::memory_order_relaxed);
+    }
+
+    bool Mutex::try_lock() {
+        bool fal = false;
+        return flag.compare_exchange_strong(fal, true, std::memory_order_relaxed);
+    }
+
     Settings::Settings(const int preferenceFd) {
         tinyxml2::XMLDocument pref;
         if (pref.LoadFile(fdopen(preferenceFd, "r")))

app/src/main/cpp/skyline/common.h

@@ -5,6 +5,7 @@
 #include <vector>
 #include <fstream>
 #include <syslog.h>
+#import <thread>
 #include <string>
 #include <sstream>
 #include <memory>
@@ -113,7 +114,31 @@ namespace skyline {
     enum class Sreg { Sp, Pc, PState };
 
     /**
-     * @brief The Logger class is to write log output
+     * @brief The Mutex class is a wrapper around an atomic bool used for synchronization
+     */
+    class Mutex {
+        std::atomic<bool> flag{false}; //!< This atomic bool holds the status of the lock
+
+      public:
+        /**
+         * @brief Wait on and lock the mutex
+         */
+        void lock();
+
+        /**
+         * @brief Lock the mutex if it is unlocked else return
+         * @return If the mutex was successfully locked or not
+         */
+        bool try_lock();
+
+        /**
+         * @brief Unlock the mutex if it is held by this thread
+         */
+        void unlock();
+    };
+
+    /**
+     * @brief The Logger class is to write log output to file and logcat
      */
     class Logger {
       private:

app/src/main/cpp/skyline/gpu.cpp

@@ -8,9 +8,10 @@
 #include <android/native_window_jni.h>
 
 extern bool Halt;
+extern jobject Surface;
 
 namespace skyline::gpu {
-    GPU::GPU(const DeviceState &state) : state(state), window(ANativeWindow_fromSurface(state.jvmManager->env, state.jvmManager->GetField("surface", "Landroid/view/Surface;"))), bufferQueue(state), vsyncEvent(std::make_shared<kernel::type::KEvent>(state)), bufferEvent(std::make_shared<kernel::type::KEvent>(state)) {
+    GPU::GPU(const DeviceState &state) : state(state), window(ANativeWindow_fromSurface(state.jvmManager->GetEnv(), Surface)), bufferQueue(state), vsyncEvent(std::make_shared<kernel::type::KEvent>(state)), bufferEvent(std::make_shared<kernel::type::KEvent>(state)) {
         ANativeWindow_acquire(window);
         resolution.width = static_cast<u32>(ANativeWindow_getWidth(window));
         resolution.height = static_cast<u32>(ANativeWindow_getHeight(window));
@@ -23,16 +24,16 @@ namespace skyline::gpu {
 
     void GPU::Loop() {
         if (surfaceUpdate) {
-            if (!state.jvmManager->CheckNull("surface", "Landroid/view/Surface;")) {
-                window = ANativeWindow_fromSurface(state.jvmManager->env, state.jvmManager->GetField("surface", "Landroid/view/Surface;"));
+            if (state.jvmManager->CheckNull(Surface))
+                return;
+            window = ANativeWindow_fromSurface(state.jvmManager->GetEnv(), Surface);
             ANativeWindow_acquire(window);
             resolution.width = static_cast<u32>(ANativeWindow_getWidth(window));
             resolution.height = static_cast<u32>(ANativeWindow_getHeight(window));
             format = ANativeWindow_getFormat(window);
+            surfaceUpdate = true;
         } else
-                return;
-        } else
-            surfaceUpdate = state.jvmManager->CheckNull("surface", "Landroid/view/Surface;");
+            surfaceUpdate = state.jvmManager->CheckNull(Surface);
         if (!bufferQueue.displayQueue.empty()) {
             auto &buffer = bufferQueue.displayQueue.front();
             bufferQueue.displayQueue.pop();

app/src/main/cpp/skyline/jvm.cpp

@@ -1,7 +1,27 @@
 #include "jvm.h"
 
+thread_local JNIEnv *env;
+
 namespace skyline {
-    JvmManager::JvmManager(JNIEnv *env, jobject instance) : env(env), instance(instance), instanceClass(env->GetObjectClass(instance)) {}
+    JvmManager::JvmManager(JNIEnv *environ, jobject instance) : instance(instance), instanceClass(reinterpret_cast<jclass>(environ->NewGlobalRef(environ->GetObjectClass(instance)))) {
+        env = environ;
+        if(env->GetJavaVM(&vm) < 0)
+            throw exception("Cannot get JavaVM from environment");
+    }
+
+    void JvmManager::AttachThread() {
+        if(!env)
+            vm->AttachCurrentThread(&env, nullptr);
+    }
+
+    void JvmManager::DetachThread() {
+        if(env)
+            vm->DetachCurrentThread();
+    }
+
+    JNIEnv* JvmManager::GetEnv() {
+        return env;
+    }
 
     jobject JvmManager::GetField(const char *key, const char *signature) {
         return env->GetObjectField(instance, env->GetFieldID(instanceClass, key, signature));
@@ -10,4 +30,8 @@ namespace skyline {
     bool JvmManager::CheckNull(const char *key, const char *signature) {
         return env->IsSameObject(env->GetObjectField(instance, env->GetFieldID(instanceClass, key, signature)), nullptr);
     }
+
+    bool JvmManager::CheckNull(jobject& object) {
+        return env->IsSameObject(object, nullptr);
+    }
 }

app/src/main/cpp/skyline/jvm.h

@@ -9,7 +9,7 @@ namespace skyline {
      */
     class JvmManager {
       public:
-        JNIEnv *env; //!< A pointer to the JNI environment
+        JavaVM *vm{}; //!< A pointer to the Java VM
         jobject instance; //!< A reference to the activity
         jclass instanceClass; //!< The class of the activity
 
@@ -19,6 +19,21 @@ namespace skyline {
          */
         JvmManager(JNIEnv *env, jobject instance);
 
+        /**
+         * @brief Attach the current thread to the Java VM
+         */
+        void AttachThread();
+
+        /**
+         * @brief Detach the current thread to the Java VM
+         */
+        void DetachThread();
+
+        /**
+         * @brief Returns a pointer to the JNI environment for the current thread
+         */
+        JNIEnv* GetEnv();
+
         /**
          * @brief Retrieves a specific field of the given type from the activity
          * @tparam objectType The type of the object in the field
@@ -27,6 +42,7 @@ namespace skyline {
          */
         template<typename objectType>
         inline objectType GetField(const char *key) {
+            JNIEnv *env = GetEnv();
             if constexpr(std::is_same<objectType, jboolean>())
                 return env->GetBooleanField(instance, env->GetFieldID(instanceClass, key, "Z"));
             else if constexpr(std::is_same<objectType, jbyte>())
@@ -60,5 +76,12 @@ namespace skyline {
          * @return If the field is null or not
          */
         bool CheckNull(const char *key, const char *signature);
+
+        /**
+         * @brief Checks if a specific jobject is null or not
+         * @param object The jobject to check
+         * @return If the object is null or not
+         */
+        bool CheckNull(jobject &object);
     };
 }

app/src/main/cpp/skyline/nce.cpp

@@ -6,10 +6,9 @@
 #include "guest.h"
 
 extern bool Halt;
-extern std::mutex jniMtx;
+extern skyline::Mutex jniMtx;
 
 namespace skyline {
-
     namespace instr {
         /**
          * @brief A bit-field struct that encapsulates a BRK instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/brk-breakpoint-instruction.
@@ -205,7 +204,7 @@ namespace skyline {
     void NCE::Execute() {
         int status = 0;
         while (!Halt && !state.os->processMap.empty()) {
-            jniMtx.lock();
+            std::lock_guard jniGd(jniMtx);
             for (const auto &process : state.os->processMap) {
                 state.os->thisProcess = process.second;
                 state.os->thisThread = process.second->threadMap.at(process.first);
@@ -263,8 +262,6 @@ namespace skyline {
             }
             state.os->serviceManager.Loop();
             state.gpu->Loop();
-            Halt = state.jvmManager->GetField<jboolean>("halt");
-            jniMtx.unlock();
         }
         for (const auto &process : state.os->processMap) {
             state.os->KillThread(process.first);
@@ -406,8 +403,7 @@ namespace skyline {
         u32 *end = address + (code.size() / sizeof(u32));
         i64 patchOffset = offset;
 
-        std::vector<u32> patch;
-        patch.resize((guest::saveCtxSize + guest::loadCtxSize) / sizeof(u32));
+        std::vector<u32> patch((guest::saveCtxSize + guest::loadCtxSize) / sizeof(u32));
         std::memcpy(patch.data(), reinterpret_cast<void*>(&guest::saveCtx), guest::saveCtxSize);
         offset += guest::saveCtxSize;
 

app/src/main/java/emu/skyline/GameActivity.kt

@@ -24,13 +24,12 @@ class GameActivity : AppCompatActivity(), SurfaceHolder.Callback, InputQueue.Cal
     private lateinit var preferenceFd: ParcelFileDescriptor
     private lateinit var logFd: ParcelFileDescriptor
     private var surface: Surface? = null
-    private var inputQueue: Long? = null
+    private var inputQueue: Long = 0L
     private lateinit var gameThread: Thread
-    private var halt: Boolean = false
 
     private external fun executeRom(romString: String, romType: Int, romFd: Int, preferenceFd: Int, logFd: Int)
-    private external fun lockMutex()
-    private external fun unlockMutex()
+    private external fun setHalt(halt: Boolean)
+    private external fun setSurface(surface: Surface?)
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -56,7 +55,7 @@ class GameActivity : AppCompatActivity(), SurfaceHolder.Callback, InputQueue.Cal
 
     override fun onDestroy() {
         super.onDestroy()
-        halt = true
+        setHalt(true)
         gameThread.join()
         romFd.close()
         preferenceFd.close()
@@ -65,9 +64,8 @@ class GameActivity : AppCompatActivity(), SurfaceHolder.Callback, InputQueue.Cal
 
     override fun surfaceCreated(holder: SurfaceHolder?) {
         Log.d("surfaceCreated", "Holder: ${holder.toString()}")
-        lockMutex()
         surface = holder!!.surface
-        unlockMutex()
+        setSurface(surface)
     }
 
     override fun surfaceChanged(holder: SurfaceHolder?, format: Int, width: Int, height: Int) {
@@ -76,9 +74,8 @@ class GameActivity : AppCompatActivity(), SurfaceHolder.Callback, InputQueue.Cal
 
     override fun surfaceDestroyed(holder: SurfaceHolder?) {
         Log.d("surfaceDestroyed", "Holder: ${holder.toString()}")
-        lockMutex()
         surface = null
-        unlockMutex()
+        setSurface(surface)
     }
 
     override fun onInputQueueCreated(queue: InputQueue?) {
@@ -86,10 +83,12 @@ class GameActivity : AppCompatActivity(), SurfaceHolder.Callback, InputQueue.Cal
         val clazz = Class.forName("android.view.InputQueue")
         val method: Method = clazz.getMethod("getNativePtr")
         inputQueue = method.invoke(queue)!! as Long
+        //setQueue(inputQueue)
     }
 
     override fun onInputQueueDestroyed(queue: InputQueue?) {
         Log.d("onInputQueueDestroyed", "InputQueue: ${queue.toString()}")
-        inputQueue = null
+        inputQueue = 0L
+        //setQueue(inputQueue)
     }
 }

build.gradle

@@ -8,7 +8,7 @@ buildscript {
 
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.5.2'
+        classpath 'com.android.tools.build:gradle:3.5.3'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong