Implement KCriticalSection (mostly)

mesosphere/source/threading/KCriticalSection.cpp

@@ -0,0 +1,45 @@
+#include <mesosphere/threading/KCriticalSection.hpp>
+#include <mesosphere/threading/KScheduler.hpp>
+#include <mesosphere/core/KCoreContext.hpp>
+
+namespace mesosphere
+{
+
+bool KCriticalSection::try_lock()
+{
+    KThread *curThread = KCoreContext::GetCurrentInstance().GetCurrentThread();
+    if (curThread == lockingThread) {
+        ++lockCount;
+        return true;
+    } else if (KInterruptSpinLock<false>::try_lock()) {
+        lockingThread = curThread;
+        lockCount = 1;
+        return true;
+    } else {
+        return false;
+    }
+}
+
+void KCriticalSection::lock()
+{
+    KThread *curThread = KCoreContext::GetCurrentInstance().GetCurrentThread();
+    if (curThread == lockingThread) {
+        ++lockCount;
+    } else {
+        KInterruptSpinLock<false>::lock();
+        lockingThread = curThread;
+        lockCount = 1;
+    }
+}
+
+void KCriticalSection::unlock()
+{
+    if (--lockCount == 0) {
+        lockingThread = nullptr;
+        KScheduler::HandleCriticalSectionLeave();
+    } else {
+        KInterruptSpinLock<false>::unlock();
+    }
+}
+
+}