From 0abcf7ea6ffdf90f4d8c240cd932018ee5186fcd 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 1/2] 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 3e4d8a7cf..20507ac7f 100644
--- a/lib/base/CMakeLists.txt
+++ b/lib/base/CMakeLists.txt
@@ -63,6 +63,7 @@ set(base_SOURCES
   shared.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 */

From b6b3ac0ab8700479fde6e0406c14eddcd2f489b9 Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Fri, 2 Oct 2020 17:53:17 +0200
Subject: [PATCH 2/2] Make ApiListener::m_ConfigSyncStageLock a SpinLock

---
 lib/remote/apilistener-filesync.cpp | 6 +++---
 lib/remote/apilistener.hpp          | 6 ++++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/lib/remote/apilistener-filesync.cpp b/lib/remote/apilistener-filesync.cpp
index ab1d5c728..28d903c19 100644
--- a/lib/remote/apilistener-filesync.cpp
+++ b/lib/remote/apilistener-filesync.cpp
@@ -20,7 +20,7 @@ using namespace icinga;
 
 REGISTER_APIFUNCTION(Update, config, &ApiListener::ConfigUpdateHandler);
 
-boost::mutex ApiListener::m_ConfigSyncStageLock;
+SpinLock ApiListener::m_ConfigSyncStageLock;
 
 /**
  * Entrypoint for updating all authoritative configs from /etc/zones.d, packages, etc.
@@ -321,7 +321,7 @@ void ApiListener::HandleConfigUpdate(const MessageOrigin::Ptr& origin, const Dic
 	/* Only one transaction is allowed, concurrent message handlers need to wait.
 	 * This affects two parent endpoints sending the config in the same moment.
 	 */
-	auto lock (Shared<boost::mutex::scoped_lock>::Make(m_ConfigSyncStageLock));
+	auto lock (Shared<std::unique_lock<SpinLock>>::Make(m_ConfigSyncStageLock));
 
 	String apiZonesStageDir = GetApiZonesStageDir();
 	String fromEndpointName = origin->FromClient->GetEndpoint()->GetName();
@@ -618,7 +618,7 @@ void ApiListener::TryActivateZonesStageCallback(const ProcessResult& pr,
  *
  * @param relativePaths Required for later file operations in the callback. Provides the zone name plus path in a list.
  */
-void ApiListener::AsyncTryActivateZonesStage(const std::vector<String>& relativePaths, const Shared<boost::mutex::scoped_lock>::Ptr& lock)
+void ApiListener::AsyncTryActivateZonesStage(const std::vector<String>& relativePaths, const Shared<std::unique_lock<SpinLock>>::Ptr& lock)
 {
 	VERIFY(Application::GetArgC() >= 1);
 
diff --git a/lib/remote/apilistener.hpp b/lib/remote/apilistener.hpp
index e3a1b0d9a..86a98d23a 100644
--- a/lib/remote/apilistener.hpp
+++ b/lib/remote/apilistener.hpp
@@ -11,6 +11,7 @@
 #include "base/configobject.hpp"
 #include "base/process.hpp"
 #include "base/shared.hpp"
+#include "base/spinlock.hpp"
 #include "base/timer.hpp"
 #include "base/workqueue.hpp"
 #include "base/tcpsocket.hpp"
@@ -20,6 +21,7 @@
 #include <boost/asio/ip/tcp.hpp>
 #include <boost/asio/spawn.hpp>
 #include <boost/asio/ssl/context.hpp>
+#include <mutex>
 #include <set>
 
 namespace icinga
@@ -179,7 +181,7 @@ private:
 	void RemoveStatusFile();
 
 	/* filesync */
-	static boost::mutex m_ConfigSyncStageLock;
+	static SpinLock m_ConfigSyncStageLock;
 
 	void SyncLocalZoneDirs() const;
 	void SyncLocalZoneDir(const Zone::Ptr& zone) const;
@@ -193,7 +195,7 @@ private:
 
 	static void TryActivateZonesStageCallback(const ProcessResult& pr,
 		const std::vector<String>& relativePaths);
-	static void AsyncTryActivateZonesStage(const std::vector<String>& relativePaths, const Shared<boost::mutex::scoped_lock>::Ptr& lock);
+	static void AsyncTryActivateZonesStage(const std::vector<String>& relativePaths, const Shared<std::unique_lock<SpinLock>>::Ptr& lock);
 
 	static String GetChecksum(const String& content);
 	static bool CheckConfigChange(const ConfigDirInformation& oldConfig, const ConfigDirInformation& newConfig);