From 4af450141b960666d2aebf164c51170ea9a074df Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Fri, 2 Oct 2020 17:41:12 +0200
Subject: [PATCH] Introduce SpinLock

---
 lib/base/CMakeLists.txt |  1 +
 lib/base/spinlock.cpp   | 22 ++++++++++++++++++++++
 lib/base/spinlock.hpp   | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 lib/base/spinlock.cpp
 create mode 100644 lib/base/spinlock.hpp

diff --git a/lib/base/CMakeLists.txt b/lib/base/CMakeLists.txt
index 108ca27c1..c1f28a06d 100644
--- a/lib/base/CMakeLists.txt
+++ b/lib/base/CMakeLists.txt
@@ -64,6 +64,7 @@ set(base_SOURCES
   shared-object.hpp
   singleton.hpp
   socket.cpp socket.hpp
+  spinlock.cpp spinlock.hpp
   stacktrace.cpp stacktrace.hpp
   statsfunction.hpp
   stdiostream.cpp stdiostream.hpp
diff --git a/lib/base/spinlock.cpp b/lib/base/spinlock.cpp
new file mode 100644
index 000000000..03de2e6be
--- /dev/null
+++ b/lib/base/spinlock.cpp
@@ -0,0 +1,22 @@
+/* Icinga 2 | (c) 2020 Icinga GmbH | GPLv2+ */
+
+#include "base/spinlock.hpp"
+#include <atomic>
+
+using namespace icinga;
+
+void SpinLock::lock()
+{
+	while (m_Locked.test_and_set(std::memory_order_acquire)) {
+	}
+}
+
+bool SpinLock::try_lock()
+{
+	return !m_Locked.test_and_set(std::memory_order_acquire);
+}
+
+void SpinLock::unlock()
+{
+	m_Locked.clear(std::memory_order_release);
+}
diff --git a/lib/base/spinlock.hpp b/lib/base/spinlock.hpp
new file mode 100644
index 000000000..d6da5876e
--- /dev/null
+++ b/lib/base/spinlock.hpp
@@ -0,0 +1,35 @@
+/* Icinga 2 | (c) 2020 Icinga GmbH | GPLv2+ */
+
+#ifndef SPINLOCK_H
+#define SPINLOCK_H
+
+#include <atomic>
+
+namespace icinga
+{
+
+/**
+ * A spin lock.
+ *
+ * @ingroup base
+ */
+class SpinLock
+{
+public:
+	SpinLock() = default;
+	SpinLock(const SpinLock&) = delete;
+	SpinLock& operator=(const SpinLock&) = delete;
+	SpinLock(SpinLock&&) = delete;
+	SpinLock& operator=(SpinLock&&) = delete;
+
+	void lock();
+	bool try_lock();
+	void unlock();
+
+private:
+	std::atomic_flag m_Locked = ATOMIC_FLAG_INIT;
+};
+
+}
+
+#endif /* SPINLOCK_H */