From 54f3b551ef9e16a99391a30555d3f67a0a23c52d Mon Sep 17 00:00:00 2001
From: Eberhard Graether <egraether@gmail.com>
Date: Tue, 16 Oct 2018 15:20:48 +0200
Subject: [PATCH] src: Fixed shared memory garbage collector mutex stuck

* Try unlocking mutex 5 times
* Then force ownership
* If everything fails run without garbage collector
---
 src/lib/Application.cpp                       |  2 +-
 src/lib/utility/interprocess/SharedMemory.cpp | 31 +++++++++++++++++--
 src/lib/utility/interprocess/SharedMemory.h   |  2 +-
 .../SharedMemoryGarbageCollector.cpp          | 10 ++++--
 4 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/src/lib/Application.cpp b/src/lib/Application.cpp
index 29979deb..71dc0617 100644
--- a/src/lib/Application.cpp
+++ b/src/lib/Application.cpp
@@ -134,7 +134,7 @@ Application::~Application()
 		m_mainView->saveLayout();
 	}
 
-	SharedMemoryGarbageCollector* collector = SharedMemoryGarbageCollector::createInstance();
+	SharedMemoryGarbageCollector* collector = SharedMemoryGarbageCollector::getInstance();
 	if (collector)
 	{
 		collector->stop();
diff --git a/src/lib/utility/interprocess/SharedMemory.cpp b/src/lib/utility/interprocess/SharedMemory.cpp
index b9974e12..cdfeaeba 100644
--- a/src/lib/utility/interprocess/SharedMemory.cpp
+++ b/src/lib/utility/interprocess/SharedMemory.cpp
@@ -168,9 +168,36 @@ SharedMemory::~SharedMemory()
 	}
 }
 
-void SharedMemory::unlockSharedMutex()
+bool SharedMemory::checkSharedMutex()
 {
-	getMutex().unlock();
+	try
+	{
+		boost::interprocess::named_mutex& mutex = getMutex();
+
+		for (size_t i = 0; i < 5; i++)
+		{
+			{
+				// try to get ownership of the mutex a couple times
+				boost::interprocess::scoped_lock<boost::interprocess::named_mutex> lock(mutex, boost::interprocess::try_to_lock);
+				if (lock.owns()) // mutex successfully locked
+				{
+					return true;
+				}
+			}
+
+			std::this_thread::sleep_for(std::chrono::milliseconds(250));
+		}
+
+		// locking kept failing, try to get ownership
+		boost::interprocess::scoped_lock<boost::interprocess::named_mutex> lock(mutex, boost::interprocess::accept_ownership);
+		return true;
+	}
+	catch (boost::interprocess::interprocess_exception& e)
+	{
+		LOG_ERROR_STREAM(<< "boost exception thrown at shared mutex check: " << e.what());
+	}
+
+	return false;
 }
 
 std::string SharedMemory::getMemoryName() const
diff --git a/src/lib/utility/interprocess/SharedMemory.h b/src/lib/utility/interprocess/SharedMemory.h
index 863a9222..68ad08ef 100644
--- a/src/lib/utility/interprocess/SharedMemory.h
+++ b/src/lib/utility/interprocess/SharedMemory.h
@@ -100,7 +100,7 @@ public:
 		std::string m_memoryName;
 	};
 
-	void unlockSharedMutex();
+	bool checkSharedMutex();
 
 private:
 	static const char* s_memoryNamePrefix;
diff --git a/src/lib/utility/interprocess/SharedMemoryGarbageCollector.cpp b/src/lib/utility/interprocess/SharedMemoryGarbageCollector.cpp
index e6593bda..2281c2c0 100644
--- a/src/lib/utility/interprocess/SharedMemoryGarbageCollector.cpp
+++ b/src/lib/utility/interprocess/SharedMemoryGarbageCollector.cpp
@@ -22,10 +22,17 @@ SharedMemoryGarbageCollector* SharedMemoryGarbageCollector::createInstance()
 		if (!s_instance)
 		{
 			s_instance = std::shared_ptr<SharedMemoryGarbageCollector>(new SharedMemoryGarbageCollector());
+
+			if (!s_instance->m_memory.checkSharedMutex())
+			{
+				LOG_ERROR_STREAM(<< "Shared memory mutex check failed. Shared memory garbage collection disabled.");
+				s_instance.reset();
+			}
 		}
 	}
-	catch (boost::interprocess::interprocess_exception)
+	catch (boost::interprocess::interprocess_exception& e)
 	{
+		LOG_ERROR_STREAM(<< "boost exception thrown at shared memory garbage collector: " << e.what());
 	}
 
 	return s_instance.get();
@@ -40,7 +47,6 @@ SharedMemoryGarbageCollector::SharedMemoryGarbageCollector()
 	: m_memory(getMemoryName(), 65536 /* 64 kB */, SharedMemory::OPEN_OR_CREATE)
 	, m_loopIsRunning(false)
 {
-	m_memory.unlockSharedMutex();
 }
 
 SharedMemoryGarbageCollector::~SharedMemoryGarbageCollector()