1 files changed, 136 insertions, 0 deletions
diff --git a/Kernel/SpinLock.h b/Kernel/SpinLock.h
new file mode 100644
index 0000000000..fa2c5d9dfc
--- /dev/null
+++ b/Kernel/SpinLock.h
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <AK/Atomic.h>
+#include <Kernel/Forward.h>
+#include <Kernel/Arch/i386/CPU.h>
+
+namespace Kernel {
+
+template <typename BaseType = u32>
+class SpinLock
+{
+    AK::Atomic<BaseType> m_lock{0};
+
+public:
+    SpinLock() = default;
+    SpinLock(const SpinLock&) = delete;
+    SpinLock(SpinLock&&) = delete;
+
+    ALWAYS_INLINE void lock()
+    {
+        BaseType expected;
+        do {
+            expected = 0;
+        } while (!m_lock.compare_exchange_strong(expected, 1, AK::memory_order_acq_rel));
+        
+    }
+
+    ALWAYS_INLINE void unlock()
+    {
+        ASSERT(is_locked());
+        m_lock.store(0, AK::memory_order_release);
+    }
+
+    ALWAYS_INLINE bool is_locked() const
+    {
+        return m_lock.load(AK::memory_order_consume) != 0;
+    }
+
+    ALWAYS_INLINE void initialize()
+    {
+        m_lock.store(0, AK::memory_order_release);
+    }
+};
+
+template <typename BaseType = u32, typename LockType = SpinLock<BaseType>>
+class ScopedSpinLock
+{
+    LockType* m_lock;
+    bool m_have_lock{false};
+    bool m_flag{false};
+
+public:
+    ScopedSpinLock() = delete;
+
+    ScopedSpinLock(LockType& lock):
+        m_lock(&lock)
+    {
+        ASSERT(m_lock);
+        m_flag = cli_and_save_interrupt_flag();
+        m_lock->lock();
+        m_have_lock = true;
+    }
+
+    ScopedSpinLock(ScopedSpinLock&& from):
+        m_lock(from.m_lock),
+        m_have_lock(from.m_have_lock),
+        m_flag(from.m_flag)
+    {
+        from.m_lock = nullptr;
+        from.m_have_lock = false;
+        from.m_flag = false;
+    }
+
+    ScopedSpinLock(const ScopedSpinLock&) = delete;
+
+    ~ScopedSpinLock()
+    {
+        if (m_lock && m_have_lock) {
+            m_lock->unlock();
+            restore_interrupt_flag(m_flag);
+        }
+    }
+
+    ALWAYS_INLINE void lock()
+    {
+        ASSERT(m_lock);
+        ASSERT(!m_have_lock);
+        m_flag = cli_and_save_interrupt_flag();
+        m_lock->lock();
+        m_have_lock = true;
+    }
+
+    ALWAYS_INLINE void unlock()
+    {
+        ASSERT(m_lock);
+        ASSERT(m_have_lock);
+        m_lock->unlock();
+        m_have_lock = false;
+        restore_interrupt_flag(m_flag);
+        m_flag = false;
+    }
+
+    ALWAYS_INLINE bool have_lock() const
+    {
+        return m_have_lock;
+    }
+};
+
+}