From f97515bd7ea7dc439adfc089e6a737ad16a0283e Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 17 Dec 2022 10:52:40 +0100
Subject: [PATCH] Kernel: Add Spinlock and LockedValue<T>

---
 kernel/CMakeLists.txt          |  1 +
 kernel/src/thread/Spinlock.cpp | 22 +++++++++
 kernel/src/thread/Spinlock.h   | 86 ++++++++++++++++++++++++++++++++++
 3 files changed, 109 insertions(+)
 create mode 100644 kernel/src/thread/Spinlock.cpp
 create mode 100644 kernel/src/thread/Spinlock.h

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index f4a7e678..89c601ee 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -12,6 +12,7 @@ set(SOURCES
     src/boot/Init.cpp
     src/arch/Serial.cpp
     src/arch/Timer.cpp
+    src/thread/Spinlock.cpp
     src/thread/Thread.cpp
     src/thread/Scheduler.cpp
 )
diff --git a/kernel/src/thread/Spinlock.cpp b/kernel/src/thread/Spinlock.cpp
new file mode 100644
index 00000000..7c70e08f
--- /dev/null
+++ b/kernel/src/thread/Spinlock.cpp
@@ -0,0 +1,22 @@
+#include "thread/Spinlock.h"
+#include "Log.h"
+#include "arch/CPU.h"
+
+void Spinlock::lock()
+{
+    int expected = -1;
+    while (!m_lock.compare_exchange_strong(expected, 0))
+    {
+        expected = -1;
+        CPU::pause();
+    }
+}
+
+void Spinlock::unlock()
+{
+    int expected = 0;
+    if (!m_lock.compare_exchange_strong(expected, -1))
+    {
+        kwarnln("Spinlock::unlock() called on an unlocked lock with value %d", expected);
+    }
+}
\ No newline at end of file
diff --git a/kernel/src/thread/Spinlock.h b/kernel/src/thread/Spinlock.h
new file mode 100644
index 00000000..984b6ce3
--- /dev/null
+++ b/kernel/src/thread/Spinlock.h
@@ -0,0 +1,86 @@
+#pragma once
+#include <luna/Atomic.h>
+
+class Spinlock
+{
+  public:
+    void lock();
+    void unlock();
+
+    bool is_locked() const
+    {
+        return m_lock.load() != -1;
+    }
+
+    // Call this before use if the Spinlock is a global variable.
+    void init()
+    {
+        m_lock = -1;
+    }
+
+  private:
+    Atomic<int> m_lock{-1};
+};
+
+template <typename T> class LockedValue
+{
+    struct LockedValueGuard
+    {
+        LockedValueGuard(LockedValue& value_ref) : m_value_ref(value_ref)
+        {
+        }
+
+        ~LockedValueGuard()
+        {
+            m_value_ref.m_lock.unlock();
+        }
+
+        T& ref()
+        {
+            return m_value_ref.m_value;
+        }
+
+        void set(const T& other)
+        {
+            ref() = other;
+        }
+
+        T* operator->()
+        {
+            return &ref();
+        }
+
+        T& operator*()
+        {
+            return ref();
+        }
+
+      private:
+        LockedValue& m_value_ref;
+    };
+
+  public:
+    LockedValue() : m_value()
+    {
+    }
+
+    LockedValue(T value) : m_value(value)
+    {
+    }
+
+    // Call this before use if the LockedValue is a global variable.
+    void init()
+    {
+        m_lock.init();
+    }
+
+    LockedValueGuard lock()
+    {
+        m_lock.lock();
+        return {*this};
+    }
+
+  private:
+    T m_value;
+    Spinlock m_lock;
+};
\ No newline at end of file