Kernel: Introduce spin-locked contended and locked resource concepts

Author: https://github.com/boricj
Commit: https://github.com/SerenityOS/serenity/commit/019ad8a507a
Pull-request: https://github.com/SerenityOS/serenity/pull/8851
Reviewed-by: https://github.com/awesomekling ✅
Reviewed-by: https://github.com/bgianfo

Kernel/Locking/SpinLockProtectedValue.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Locking/SpinLockResource.h>
+
+namespace Kernel {
+
+template<typename T>
+class SpinLockProtectedValue : private T
+    , public SpinLockContendedResource {
+    AK_MAKE_NONCOPYABLE(SpinLockProtectedValue);
+    AK_MAKE_NONMOVABLE(SpinLockProtectedValue);
+
+protected:
+    using LockedConst = SpinLockLockedResource<T const>;
+    using LockedMutable = SpinLockLockedResource<T>;
+
+    LockedConst lock_const() const { return LockedConst(static_cast<T const*>(this), this->SpinLockContendedResource::m_spinlock); }
+    LockedMutable lock_mutable() { return LockedMutable(static_cast<T*>(this), this->SpinLockContendedResource::m_spinlock); }
+
+public:
+    using T::T;
+
+    SpinLockProtectedValue() = default;
+
+    template<typename Callback>
+    decltype(auto) with(Callback callback) const
+    {
+        auto lock = lock_const();
+        return callback(*lock);
+    }
+
+    template<typename Callback>
+    decltype(auto) with(Callback callback)
+    {
+        auto lock = lock_mutable();
+        return callback(*lock);
+    }
+
+    template<typename Callback>
+    void for_each_const(Callback callback) const
+    {
+        with([&](const auto& value) {
+            for (auto& item : value)
+                callback(item);
+        });
+    }
+
+    template<typename Callback>
+    void for_each(Callback callback)
+    {
+        with([&](auto& value) {
+            for (auto& item : value)
+                callback(item);
+        });
+    }
+};
+
+}

Kernel/Locking/SpinLockResource.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/StdLibExtras.h>
+#include <Kernel/Locking/SpinLock.h>
+
+namespace Kernel {
+
+template<typename T>
+class SpinLockLockedResource {
+    AK_MAKE_NONCOPYABLE(SpinLockLockedResource);
+
+public:
+    SpinLockLockedResource(T* value, RecursiveSpinLock& spinlock)
+        : m_value(value)
+        , m_scoped_spinlock(spinlock)
+    {
+    }
+
+    ALWAYS_INLINE T const* operator->() const { return m_value; }
+    ALWAYS_INLINE T const& operator*() const { return *m_value; }
+
+    ALWAYS_INLINE T* operator->() { return m_value; }
+    ALWAYS_INLINE T& operator*() { return *m_value; }
+
+    ALWAYS_INLINE T const* get() const { return m_value; }
+    ALWAYS_INLINE T* get() { return m_value; }
+
+private:
+    T* m_value;
+    ScopedSpinLock<RecursiveSpinLock> m_scoped_spinlock;
+};
+
+class SpinLockContendedResource {
+    template<typename>
+    friend class SpinLockLockedResource;
+
+    AK_MAKE_NONCOPYABLE(SpinLockContendedResource);
+    AK_MAKE_NONMOVABLE(SpinLockContendedResource);
+
+public:
+    SpinLockContendedResource() = default;
+
+protected:
+    mutable RecursiveSpinLock m_spinlock;
+};
+
+}