Dbg:traceContinHistForDeadlock: consult LockUsageDesc::hasBeenReleased

Don't raise the alarm for a deadlock if the lock has already been
released at the moment of checking.

include/spinscale/lockSet.h

@@ -197,15 +197,52 @@ public:
 		allLocksAcquired = false;
 	}
 
-	const LockUsageDesc &getLockUsageDesc(const Qutex &criterionLock) const
+	std::optional<std::reference_wrapper<LockUsageDesc>>
+	findLockUsageDesc(const Qutex &criterionLock)
 	{
 		for (auto& lockUsageDesc : locks)
 		{
 			if (&lockUsageDesc.qutex.get() == &criterionLock) {
-				return lockUsageDesc;
+				return std::ref(lockUsageDesc);
 			}
 		}
 
+		return std::nullopt;
+	}
+
+	std::optional<std::reference_wrapper<const LockUsageDesc>>
+	findLockUsageDesc(const Qutex &criterionLock) const
+	{
+		for (const auto& lockUsageDesc : locks)
+		{
+			if (&lockUsageDesc.qutex.get() == &criterionLock) {
+				return std::cref(lockUsageDesc);
+			}
+		}
+
+		return std::nullopt;
+	}
+
+	LockUsageDesc &getLockUsageDesc(const Qutex &criterionLock)
+	{
+		auto lockUsageDesc = findLockUsageDesc(criterionLock);
+		if (lockUsageDesc.has_value()) {
+			return lockUsageDesc->get();
+		}
+
+		// Should never happen if the LockSet is properly constructed
+		throw std::runtime_error(
+			std::string(__func__) +
+			": Qutex not found in this LockSet");
+	}
+
+	const LockUsageDesc &getLockUsageDesc(const Qutex &criterionLock) const
+	{
+		auto lockUsageDesc = findLockUsageDesc(criterionLock);
+		if (lockUsageDesc.has_value()) {
+			return lockUsageDesc->get();
+		}
+
 		// Should never happen if the LockSet is properly constructed
 		throw std::runtime_error(
 			std::string(__func__) +
@@ -225,8 +262,7 @@ public:
 				": LockSet::releaseQutexEarly() called but allLocksAcquired is false");
 		}
 
-		auto& lockUsageDesc = const_cast<LockUsageDesc&>(
-			getLockUsageDesc(qutex));
+		auto& lockUsageDesc = getLockUsageDesc(qutex);
 
 		if (!lockUsageDesc.hasBeenReleased)
 		{

include/spinscale/serializedAsynchronousContinuation.h

@@ -335,11 +335,12 @@ SerializedAsynchronousContinuation<OriginalCbFnT>
 		auto heldLockSet = currContin->getLockSet();
 		if (!heldLockSet.has_value()) { continue; }
 
-		// Check if the firstFailedQutex is in this continuation's LockSet
-		try {
-			heldLockSet->get().getLockUsageDesc(firstFailedQutex);
-		} catch (const std::runtime_error& e) {
-			std::cerr << __func__ << ": " << e.what() << std::endl;
+			// A miss is expected here; only a hit indicates a potential deadlock.
+			auto lockUsageDesc = heldLockSet->get().findLockUsageDesc(
+				firstFailedQutex);
+			if (!lockUsageDesc.has_value()
+				|| lockUsageDesc->get().hasBeenReleased)
+			{
 				continue;
 			}
 
@@ -434,10 +435,10 @@ SerializedAsynchronousContinuation<OriginalCbFnT>
 			auto heldLockSet = currContin->getLockSet();
 			if (!heldLockSet.has_value()) { continue; }
 
-			// Check if this continuation holds the foreign lock
-			try {
-				const auto& lockUsageDesc = heldLockSet
-					->get().getLockUsageDesc(foreignLock);
+			// A miss is expected here; a hit indicates a potential gridlock.
+			auto lockUsageDesc = heldLockSet->get().findLockUsageDesc(
+				foreignLock);
+			if (!lockUsageDesc.has_value()) { continue; }
 
 			// Matched! We hold a lock that the foreign owner is waiting for
 			std::cout << __func__ << ": Gridlock detected: We hold lock @"
@@ -449,10 +450,6 @@ SerializedAsynchronousContinuation<OriginalCbFnT>
 				<< std::endl;
 
 			return true;
-			} catch (const std::runtime_error& e) {
-				// This continuation doesn't hold the foreign lock. Continue.
-				continue;
-			}
 		}
 	}