Move Lock from AK to Kernel, since it only works inside the kernel.

Kernel/Lock.h

@@ -0,0 +1,113 @@
+#pragma once
+
+#include <AK/Assertions.h>
+#include <AK/Types.h>
+#include <Kernel/i386.h>
+#include <Kernel/Scheduler.h>
+
+class Process;
+extern Process* current;
+
+static inline dword CAS(volatile dword* mem, dword newval, dword oldval)
+{
+    dword ret;
+    asm volatile(
+        "cmpxchgl %2, %1"
+        :"=a"(ret), "+m"(*mem)
+        :"r"(newval), "0"(oldval)
+        :"cc", "memory");
+    return ret;
+}
+
+class Lock {
+public:
+    Lock(const char* name = nullptr) : m_name(name) { }
+    ~Lock() { }
+
+    void lock();
+    void unlock();
+
+    const char* name() const { return m_name; }
+
+private:
+    volatile dword m_lock { 0 };
+    dword m_level { 0 };
+    Process* m_holder { nullptr };
+    const char* m_name { nullptr };
+};
+
+class Locker {
+public:
+    [[gnu::always_inline]] inline explicit Locker(Lock& l) : m_lock(l) { lock(); }
+    [[gnu::always_inline]] inline ~Locker() { unlock(); }
+    [[gnu::always_inline]] inline void unlock() { m_lock.unlock(); }
+    [[gnu::always_inline]] inline void lock() { m_lock.lock(); }
+
+private:
+    Lock& m_lock;
+};
+
+[[gnu::always_inline]] inline void Lock::lock()
+{
+    if (!are_interrupts_enabled()) {
+        kprintf("Interrupts disabled when trying to take Lock{%s}\n", m_name);
+        hang();
+    }
+    ASSERT(!Scheduler::is_active());
+    for (;;) {
+        if (CAS(&m_lock, 1, 0) == 0) {
+            if (!m_holder || m_holder == current) {
+                m_holder = current;
+                ++m_level;
+                memory_barrier();
+                m_lock = 0;
+                return;
+            }
+            m_lock = 0;
+        }
+        Scheduler::donate_to(m_holder, m_name);
+    }
+}
+
+inline void Lock::unlock()
+{
+    for (;;) {
+        if (CAS(&m_lock, 1, 0) == 0) {
+            ASSERT(m_holder == current);
+            ASSERT(m_level);
+            --m_level;
+            if (m_level) {
+                memory_barrier();
+                m_lock = 0;
+                return;
+            }
+            m_holder = nullptr;
+            memory_barrier();
+            m_lock = 0;
+            return;
+        }
+        Scheduler::donate_to(m_holder, m_name);
+    }
+}
+
+#define LOCKER(lock) Locker locker(lock)
+
+template<typename T>
+class Lockable {
+public:
+    Lockable() { }
+    Lockable(T&& resource) : m_resource(move(resource)) { }
+    Lock& lock() { return m_lock; }
+    T& resource() { return m_resource; }
+
+    T lock_and_copy()
+    {
+        LOCKER(m_lock);
+        return m_resource;
+    }
+
+private:
+    T m_resource;
+    Lock m_lock;
+};
+