IoUringAssmEngn: detect assembly end condition w/eventfdDesc validity

We can simplify and universalize the logic here by acknowledging that
assemblyCycleComplete() will always destroy the current eventfdDesc
object, so we can just check that to see whether we should continue
the assembly cycle.

stimBuffApis/livoxGen1/ioUringAssemblyEngine.cpp

@@ -309,7 +309,7 @@ void IoUringAssemblyEngine::assemblyCycleComplete()
 {
 	// Cancel in-flight stall timeout timer
 	stallTimer.cancel();
-	onCqeReadyCallback = std::move([](void *, int, bool&){});
+	onCqeReadyCallback = std::move([](void *, int){});
 
 	if (frameAssemblyDesc)
 	{
@@ -441,8 +441,7 @@ public:
 		engine.resetAndAssembleFrame(
 			std::bind(&AssembleFrameReq::assembleFrameReq2_2,
 				context.get(), context,
-				std::placeholders::_1, std::placeholders::_2,
-				std::placeholders::_3));
+				std::placeholders::_1, std::placeholders::_2));
 
 		// Set up timeout timer for CONFIG_STIMBUFF_FRAME_PERIOD_MS/2 ms
 		engine.stallTimer.expires_from_now(
@@ -485,13 +484,12 @@ public:
 
 		// Set timer fired flag
 		context->timerFired.store(true);
-		bool dummyStopListening = false;  // Timer path doesn't need this
-		context->assembleFrameReq3(context, dummyStopListening);
+		context->assembleFrameReq3(context);
 	}
 
 	void assembleFrameReq2_2(
 		std::shared_ptr<AssembleFrameReq> context,
-		void *user_data, int cqe_result, bool& stopListeningOnEventFd)
+		void *user_data, int cqe_result)
 	{
 		// NB: The lock was acquired by onEventFdRead before calling this func
 		if (!context->engine.shouldAcceptRequests)
@@ -515,13 +513,12 @@ public:
 			success))
 		{
 			// Loop is complete, call oracle function
-			context->assembleFrameReq3(context, stopListeningOnEventFd);
+			context->assembleFrameReq3(context);
 		}
 	}
 
 	void assembleFrameReq3(
-		std::shared_ptr<AssembleFrameReq> context,
-		bool& stopListeningOnEventFd
+		std::shared_ptr<AssembleFrameReq> context
 		)
 	{
 		/**	EXPLANATION:
@@ -533,7 +530,6 @@ public:
 		if (context->handlerExecuted.exchange(true)) { return; }
 		// Cancel the timer, stop the engine and process frame, if any.
 		context->engine.assemblyCycleComplete();
-		stopListeningOnEventFd = true;
 
 		/**	EXPLANATION:
 		 * Timeout doesn't necessarily mean error.
@@ -665,7 +661,6 @@ void IoUringAssemblyEngine::onEventfdRead(
 	 */
 
 	// Process all available CQEs and call callback for each one
-	bool stopListeningOnEventFd = false;
 	struct io_uring_cqe *cqe;
 	while (io_uring_peek_cqe(&ring, &cqe) == 0)
 	{
@@ -689,7 +684,7 @@ void IoUringAssemblyEngine::onEventfdRead(
 		 * because of this.
 		 */
 		if (onCqeReadyCallback) {
-			onCqeReadyCallback(user_data, cqe_result, stopListeningOnEventFd);
+			onCqeReadyCallback(user_data, cqe_result);
 		}
 	}
 
@@ -697,7 +692,11 @@ void IoUringAssemblyEngine::onEventfdRead(
 	 * But we do put a `return` here because we know that at this point, the
 	 * caller's callback has already been invoked.
 	 */
-	if (!shouldAcceptRequests || stopListeningOnEventFd) { return; }
+	if (!shouldAcceptRequests
+		|| eventfdDesc == nullptr || !eventfdDesc->is_open())
+	{
+		return;
+	}
 
 	// Re-arm the eventfd read for next CQE notification
 	eventfdDesc->async_read_some(

stimBuffApis/livoxGen1/ioUringAssemblyEngine.h

@@ -47,7 +47,7 @@ public:
 		{ return nSucceeded != 0 && nTotal != 0 && nSucceeded != nTotal; }
 
 private:
-	typedef std::function<void(void*, int, bool&)> resetAndAssembleFrameCbFn;
+	typedef std::function<void(void*, int)> resetAndAssembleFrameCbFn;
 	void resetAndAssembleFrame(resetAndAssembleFrameCbFn onCqeReady);
 	void assemblyCycleComplete();
 	bool stop();