From 282f8fd17397bb026de4845fed1de34c84716fac Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Fri, 15 Feb 2019 15:43:58 +0100
Subject: [PATCH] IoEngine: explicitly join I/O threads

---
 lib/base/io-engine.cpp | 21 ++++++++++++++++++---
 lib/base/io-engine.hpp |  9 +++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/lib/base/io-engine.cpp b/lib/base/io-engine.cpp
index daad42df0..0079ca251 100644
--- a/lib/base/io-engine.cpp
+++ b/lib/base/io-engine.cpp
@@ -99,7 +99,7 @@ boost::asio::io_service& IoEngine::GetIoService()
 	return m_IoService;
 }
 
-IoEngine::IoEngine() : m_IoService(), m_KeepAlive(m_IoService), m_AlreadyExpiredTimer(m_IoService)
+IoEngine::IoEngine() : m_IoService(), m_KeepAlive(m_IoService), m_Threads(decltype(m_Threads)::size_type(std::thread::hardware_concurrency())), m_AlreadyExpiredTimer(m_IoService)
 {
 	m_AlreadyExpiredTimer.expires_at(boost::posix_time::neg_infin);
 
@@ -111,8 +111,21 @@ IoEngine::IoEngine() : m_IoService(), m_KeepAlive(m_IoService), m_AlreadyExpired
 		m_CpuBoundSemaphore.store(concurrency - 1u);
 	}
 
-	for (auto i (std::thread::hardware_concurrency()); i; --i) {
-		std::thread(&IoEngine::RunEventLoop, this).detach();
+	for (auto& thread : m_Threads) {
+		thread = std::thread(&IoEngine::RunEventLoop, this);
+	}
+}
+
+IoEngine::~IoEngine()
+{
+	for (auto& thread : m_Threads) {
+		m_IoService.post([]() {
+			throw TerminateIoThread();
+		});
+	}
+
+	for (auto& thread : m_Threads) {
+		thread.join();
 	}
 }
 
@@ -122,6 +135,8 @@ void IoEngine::RunEventLoop()
 		try {
 			m_IoService.run();
 
+			break;
+		} catch (const TerminateIoThread&) {
 			break;
 		} catch (const std::exception& e) {
 			Log(LogCritical, "IoEngine", "Exception during I/O operation!");
diff --git a/lib/base/io-engine.hpp b/lib/base/io-engine.hpp
index e383b2e42..05610ca6f 100644
--- a/lib/base/io-engine.hpp
+++ b/lib/base/io-engine.hpp
@@ -22,7 +22,10 @@
 
 #include "base/lazy-init.hpp"
 #include <atomic>
+#include <exception>
 #include <memory>
+#include <thread>
+#include <vector>
 #include <boost/asio/deadline_timer.hpp>
 #include <boost/asio/io_service.hpp>
 #include <boost/asio/spawn.hpp>
@@ -82,6 +85,7 @@ public:
 	IoEngine(IoEngine&&) = delete;
 	IoEngine& operator=(const IoEngine&) = delete;
 	IoEngine& operator=(IoEngine&&) = delete;
+	~IoEngine();
 
 	static IoEngine& Get();
 
@@ -96,8 +100,13 @@ private:
 
 	boost::asio::io_service m_IoService;
 	boost::asio::io_service::work m_KeepAlive;
+	std::vector<std::thread> m_Threads;
 	boost::asio::deadline_timer m_AlreadyExpiredTimer;
 	std::atomic_uint_fast32_t m_CpuBoundSemaphore;
 };
 
+class TerminateIoThread : public std::exception
+{
+};
+
 #endif /* IO_ENGINE_H */