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.

smocore/lockSet.cpp

@@ -47,7 +47,9 @@ void LockSet<OriginalCbFnT>::registerInQutexQueues(
 }
 
 template <class OriginalCbFnT>
-bool LockSet<OriginalCbFnT>::tryAcquireOrBackOff(LockerAndInvokerBase &lockvoker)
+bool LockSet<OriginalCbFnT>::tryAcquireOrBackOff(
+	LockerAndInvokerBase &lockvoker, Qutex *firstFailedQutex
+	)
 {
 	if (!registeredInQutexQueues)
 	{
@@ -72,6 +74,10 @@ bool LockSet<OriginalCbFnT>::tryAcquireOrBackOff(LockerAndInvokerBase &lockvoker
 		if (!lockUsageDesc.first.get().tryAcquire(
 			lockvoker, nRequiredLocks))
 		{
+			// Set the first failed qutex for debugging
+			if (firstFailedQutex) {
+				*firstFailedQutex = &lockUsageDesc.first.get();
+			}
 			break;
 		}