Debug:Qutex: Add deadlock detection based on elapsed time

We now detect that a deadlock is likely when
CONFIG_DEBUG_QUTEX_DEADLOCK_TIMEOUT_MS has elapsed. This is the
preliminary work required to do a backtrace through the call
stack and figure out if a deadlock has really occured.

To do this, we'd have to go through the async call chain and
search for a previous caller which acquired the same qutex as
the one that first failed during this Lockvoker LockSet acquisition
attempt.

include/serializedAsynchronousContinuation.h

@@ -4,6 +4,8 @@
 #include <functional>
 #include <memory>
 #include <atomic>
+#include <chrono>
+#include <iostream>
 #include <componentThread.h>
 #include <lockSet.h>
 #include <asynchronousContinuation.h>
@@ -63,7 +65,8 @@ public:
 		:	LockerAndInvokerBase(&serializedContinuation),
 		serializedContinuation(serializedContinuation),
 		target(target),
-		invocationTarget(std::move(invocationTarget))
+		invocationTarget(std::move(invocationTarget)),
+		creationTimestamp(std::chrono::steady_clock::now())
 		{
 			firstWake();
 		}
@@ -81,11 +84,28 @@ public:
 					"executing on wrong ComponentThread");
 			}
 
+			Qutex *firstFailedQutexPtr = nullptr;
+			bool isDeadlockLikely = isDeadlockLikely();
+
 			if (!serializedContinuation.requiredLocks.tryAcquireOrBackOff(
-				*this))
+				*this, (isDeadlockLikely ? &firstFailedQutexPtr : nullptr)))
 			{
 				// Just allow this lockvoker to be dropped from its io_service.
 				allowAwakening();
+
+				if (!isDeadlockLikely)
+					{ return; }
+
+				Qutex &firstFailedQutex = *firstFailedQutexPtr;
+
+				std::cerr << __func__ << ": Deadlock likely: "
+					<< "Lockvoker has been waiting for "
+					<< std::chrono::duration_cast<std::chrono::milliseconds>(
+						std::chrono::steady_clock::now() - creationTimestamp)
+						.count()
+					<< "ms, failed on qutex @" << &firstFailedQutex
+					<< " (" << firstFailedQutex.name << ")" << std::endl;
+
 				return;
 			}
 
@@ -137,9 +157,8 @@ public:
 			target->getIoService().post(*this);
 		}
 
-		/**
-		 * @brief Allow awakening by resetting the awake flag
-		 */
+	private:
+		// Allow awakening by resetting the awake flag
 		void allowAwakening()
 			{ serializedContinuation.isAwakeOrBeingAwakened.store(false); }
 
@@ -158,11 +177,21 @@ public:
 			awaken(true);
 		}
 
+		// Check if CONFIG_QUTEX_DEADLOCK_TIMEOUT_MS has elapsed since creation
+		bool isDeadlockLikely() const
+		{
+			auto now = std::chrono::steady_clock::now();
+			auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(
+				now - creationTimestamp);
+			return elapsed.count() >= DEBUG_CONFIG_QUTEX_DEADLOCK_TIMEOUT_MS;
+		}
+
 	private:
 		SerializedAsynchronousContinuation<OriginalCbFnT>
 			&serializedContinuation;
 		InvocationTargetT invocationTarget;
 		std::shared_ptr<ComponentThread> target;
+		std::chrono::steady_clock::time_point creationTimestamp;
 	};
 };