IoUringAssmEngn: add assembleFrameReq

Invoke it instimFrameProductionTimesliceInd.

Also, we discovered:
* stream_descriptor::release() doesn't fully release all metadata
  from the fd it was assigned. This suggests that we should go
  through the codebase and do: release()=>reset() whenever we
  wish to release().
* We've confirmed that spinlocks can be used to prevent race
  conditions between stop() and handler methods.

stimBuffApis/livoxGen1/ioUringAssemblyEngine.cpp

@@ -1,3 +1,5 @@
+#include <config.h>
+#include <opts.h>
 #include <boostAsioLinkageFix.h>
 #include <cstring>
 #include <stdexcept>
@@ -11,6 +13,11 @@
 #include <boost/system/error_code.hpp>
 #include <livoxProto1/device.h>
 #include <livoxProto1/livoxProto1.h>
+#include <asynchronousContinuation.h>
+#include <asynchronousLoop.h>
+#include <asynchronousBridge.h>
+#include <callback.h>
+#include <spinLock.h>
 #include "ioUringAssemblyEngine.h"
 #include "pcloudStimulusBuffer.h"
 #include "livoxGen1.h"
@@ -41,7 +48,8 @@ IoUringAssemblyEngine::IoUringAssemblyEngine(PcloudStimulusBuffer& parent_)
 frameAssemblyDesc(nullptr), ring{},
 isSetup(false),
 eventfdFd(-1), eventfdDesc(nullptr), eventfd_value(0),
-stallTimer(parent_.device->componentThread->getIoService())
+stallTimer(parent_.device->componentThread->getIoService()),
+isAssembling(false)
 {}
 
 bool IoUringAssemblyEngine::setup()
@@ -139,7 +147,7 @@ void IoUringAssemblyEngine::finalize()
 }
 
 void IoUringAssemblyEngine::resetAndAssembleFrame(
-	std::function<void(void*)> onCqeReady)
+	resetAndAssembleFrameCbFn onCqeReady)
 {
 	if (!onCqeReady)
 	{
@@ -236,6 +244,8 @@ void IoUringAssemblyEngine::resetAndAssembleFrame(
 			+ " (errno=" + std::to_string(errno) + ")");
 	}
 
+	// Set assembly flag
+	isAssembling = true;
 	// Start listening for CQE notifications on eventfd
 	eventfdDesc->async_read_some(
 		boost::asio::buffer(&eventfd_value, sizeof(eventfd_value)),
@@ -245,8 +255,35 @@ void IoUringAssemblyEngine::resetAndAssembleFrame(
 			std::placeholders::_2));
 }
 
-void IoUringAssemblyEngine::stop()
+void IoUringAssemblyEngine::stop(bool doAcquireLock)
 {
+	// Clear assembly flag first to signal onEventfdRead to stop re-arming
+	// Acquire and release lock tightly around setting the flag
+	if (doAcquireLock)
+	{
+		SpinLock::Guard lock(isAssemblingLock);
+		isAssembling = false;
+	} else {
+		isAssembling = false;
+	}
+
+	/**	FIXME:
+	 * There's a problem with this bridge here.
+	 *
+	 * We can't delay during every call to stop because under normal operating
+	 * conditions, this whole assembly process should be able to move as fast
+	 * as possible and to receive as much data as possible without maximum
+	 * throughput.
+	 *
+	 * Yet we need to delay briefly here to ensure that the onEventfdRead loop
+	 * has a chance to see the flag and halt.
+	 *
+	 * We need to analyze this carefully and figure out what the correct
+	 * conditions are for being certain that we aren't destroying state while
+	 * the eventfdRead loop is still running; and we need to figure out how to
+	 * ensure that we only delay when absolutely necessary.
+	 */
+
 	// Cancel in-flight stall timeout timer
 	stallTimer.cancel();
 
@@ -290,7 +327,7 @@ void IoUringAssemblyEngine::stop()
 			}
 		}
 
-		if (!sawCancelCqe) {
+		if (!sawCancelCqe && OptionParser::getOptions().verbose) {
 			std::cerr << __func__ << ": no CQE seen for cancel operation\n";
 		}
 	}
@@ -307,12 +344,178 @@ cleanup_eventfd:
 		 * itself in the next resetAndAssembleFrame() cycle, so we call
 		 * release() instead of reset() to ensure that the underlying fd
 		 * is not closed.
+		 *
+		 * However, we need to close the descriptor's association with the
+		 * io_service before releasing it, otherwise Boost.Asio will complain
+		 * when we try to create a new descriptor with the same fd.
 		 */
 		eventfdDesc->cancel();
-		eventfdDesc.release();
+		eventfdDesc->release();
+		/* Destroy the descriptor object (now that it's unregistered, destroying
+		 * it won't close the fd since release() transferred ownership back)
+		 */
+		eventfdDesc.reset();
+	}
+}
+
+// Continuation class for assembleFrameReq
+class IoUringAssemblyEngine::AssembleFrameReq
+:	public PostedAsynchronousContinuation<
+		IoUringAssemblyEngine::assembleFrameReqCbFn>
+{
+public:
+	AssembleFrameReq(
+		IoUringAssemblyEngine& engine_,
+		const std::shared_ptr<ComponentThread>& caller,
+		Callback<IoUringAssemblyEngine::assembleFrameReqCbFn> cb)
+	:	PostedAsynchronousContinuation<
+			IoUringAssemblyEngine::assembleFrameReqCbFn>(caller, cb),
+	engine(engine_),
+	loop(engine_.frameAssemblyDesc->numSlots),
+	timerFired(false), handlerExecuted(false)
+	{}
+
+public:
+	void assembleFrameReq1_posted(
+		std::shared_ptr<AssembleFrameReq> context)
+	{
+		if (!engine.frameAssemblyDesc)
+		{
+			throw std::runtime_error(std::string(__func__)
+				+ ": frameAssemblyDesc is null");
 		}
 
-	onCqeReadyCallback = nullptr;
+		// Initialize loop with number of slots
+		context->loop = AsynchronousLoop(engine.frameAssemblyDesc->numSlots);
+
+		/**	FIXME:
+		 * I'm suspicious of this std::bind return object here. What if us
+		 * setting it to null inside of stop() doesn't actually cause the
+		 * object to be destroyed? This would cause this contin's sh_ptr's
+		 * reference count to never reach 0, causing a memory leak.
+		 */
+		engine.resetAndAssembleFrame(
+			std::bind(&AssembleFrameReq::assembleFrameReq2_2,
+				context.get(), context,
+				std::placeholders::_1, std::placeholders::_2));
+
+		// Set up timeout timer for CONFIG_STIMBUFF_FRAME_PERIOD_MS/2 ms
+		engine.stallTimer.expires_from_now(
+			boost::posix_time::milliseconds(
+				CONFIG_STIMBUFF_FRAME_PERIOD_MS / 2));
+		engine.stallTimer.async_wait(
+			std::bind(&AssembleFrameReq::assembleFrameReq2_1,
+				context.get(), context,
+				std::placeholders::_1));
+	}
+
+	void assembleFrameReq2_1(
+		std::shared_ptr<AssembleFrameReq> context,
+		const boost::system::error_code& error)
+	{
+		// Check if timer was cancelled (ignore if operation_aborted)
+		if (error == boost::asio::error::operation_aborted) { return; }
+
+		// Set timer fired flag
+		context->timerFired.store(true);
+		context->assembleFrameReq3(context);
+	}
+
+	void assembleFrameReq2_2(
+		std::shared_ptr<AssembleFrameReq> context,
+		void *user_data, int cqe_result)
+	{
+		(void)user_data;  // Not used - we just track success/failure counts
+
+		// Caller decides success: result >= 0 means success
+		bool success = (cqe_result >= 0);
+		if (context->loop.incrementSuccessOrFailureAndTestForCompletionDueTo(
+			success))
+		{
+			// Loop is complete, call oracle function
+			context->assembleFrameReq3(context);
+		}
+	}
+
+	void assembleFrameReq3(std::shared_ptr<AssembleFrameReq> context)
+	{
+		// Ensure we only execute once using atomic exchange
+		if (context->handlerExecuted.exchange(true)) { return; }
+		// Cancel the timer, stop the engine and process frame, if any.
+		context->engine.stop(false);
+
+		/**	EXPLANATION:
+		 * Timeout doesn't necessarily mean error.
+		 *
+		 * If we received zero dgrams from the device, that is indeed an error.
+		 * But if we received some dgrams, but not all, that is not an error:
+		 * it just means we didn't receive as much data as we would have liked.
+		 */
+
+		// Error: no slots succeeded - no data received successfully.
+		if (context->loop.nSucceeded.load() == 0)
+		{
+			context->callOriginalCb(false, context->loop);
+			return;
+		}
+
+		if (context->loop.nSucceeded.load() >= context->loop.nTotal)
+		{
+			// Success: all or more slots succeeded
+			if (context->loop.nSucceeded.load() > context->loop.nTotal)
+			{
+				std::cerr << __func__ << ": nSucceeded > nTotal: succ ("
+					<< context->loop.nSucceeded.load()
+					<< ") > nTotal (" << context->loop.nTotal << ")\n";
+			}
+
+			context->callOriginalCb(true, context->loop);
+			return;
+		}
+
+		if (context->loop.nSucceeded.load() < context->loop.nTotal)
+		{
+			// Success: some slots succeeded (less than total)
+			// Note: dummy fill for un-assembled slots will be implemented later
+			context->callOriginalCb(true, context->loop);
+			return;
+		}
+
+		if (OptionParser::getOptions().verbose)
+		{
+			std::cerr << __func__ << ": Invalid state: nSucceeded ("
+				<< context->loop.nSucceeded.load()
+				<< ") < nTotal (" << context->loop.nTotal << ")" << std::endl;
+		}
+
+		context->callOriginalCb(false, context->loop);
+		return;
+	}
+
+public:
+	IoUringAssemblyEngine& engine;
+	AsynchronousLoop loop;
+	std::atomic<bool> timerFired;
+	std::atomic<bool> handlerExecuted;
+};
+
+void IoUringAssemblyEngine::assembleFrameReq(
+	Callback<assembleFrameReqCbFn> cb)
+{
+	if (!frameAssemblyDesc)
+	{
+		throw std::runtime_error(std::string(__func__)
+			+ ": frameAssemblyDesc is null");
+	}
+
+	const auto& caller = smoHooksPtr->ComponentThread_getSelf();
+	auto request = std::make_shared<AssembleFrameReq>(
+		*this, caller, std::move(cb));
+
+	parent.device->componentThread->getIoService().post(
+		std::bind(
+			&AssembleFrameReq::assembleFrameReq1_posted,
+			request.get(), request));
 }
 
 void IoUringAssemblyEngine::onEventfdRead(
@@ -322,8 +525,15 @@ void IoUringAssemblyEngine::onEventfdRead(
 	(void)bytes_transferred;
 
 	// Ignore cancellation errors
-	if (error == boost::asio::error::operation_aborted)
-		{ return; }
+	if (error == boost::asio::error::operation_aborted) { return; }
+
+	/**	EXPLANATION:
+	 * This lock should be held throughout this method to ensure that the
+	 * IoUringAssemblyEngine's per-assembly state isn't destroyed while this
+	 * handler is running.
+	 */
+	SpinLock::Guard lock(isAssemblingLock);
+	if (!isAssembling) { return; }
 
 	/**	FIXME:
 	 * It may be necessary to specifically check for and handle the cancel op
@@ -336,11 +546,14 @@ void IoUringAssemblyEngine::onEventfdRead(
 	{
 		// Get user_data from the CQE
 		void* user_data = io_uring_cqe_get_data(cqe);
+		// Get result from the CQE
+		int cqe_result = cqe->res;
 		// Mark the CQE as seen
 		io_uring_cqe_seen(&ring, cqe);
 
 		/**	EXPLANATION:
-		 * Call the user-provided callback for this CQE with its user_data.
+		 * Call the user-provided callback for this CQE with its user_data and
+		 * result.
 		 *
 		 * 1. Notice that we call the caller's cb *after* marking the CQE as
 		 * seen. We may later need to change this if the caller needs
@@ -351,16 +564,18 @@ void IoUringAssemblyEngine::onEventfdRead(
 		 * because of this.
 		 */
 		if (onCqeReadyCallback) {
-			onCqeReadyCallback(user_data);
+			onCqeReadyCallback(user_data, cqe_result);
 		}
 	}
 
 	// Re-arm the eventfd read for next CQE notification
+	// Only re-arm if assembly is still active (stop() hasn't been called)
 	if (eventfdDesc && eventfdFd >= 0)
 	{
 		eventfdDesc->async_read_some(
 			boost::asio::buffer(&eventfd_value, sizeof(eventfd_value)),
-			std::bind(&IoUringAssemblyEngine::onEventfdRead, this,
+			std::bind(
+				&IoUringAssemblyEngine::onEventfdRead, this,
 				std::placeholders::_1,
 				std::placeholders::_2));
 	}

stimBuffApis/livoxGen1/ioUringAssemblyEngine.h

@@ -14,6 +14,10 @@
 #include <boost/asio/deadline_timer.hpp>
 #include <boost/asio/posix/stream_descriptor.hpp>
 #include <livoxProto1/device.h>
+#include <asynchronousContinuation.h>
+#include <asynchronousLoop.h>
+#include <callback.h>
+#include <spinLock.h>
 #include "frameAssemblyDesc.h"
 
 namespace smo {
@@ -29,9 +33,13 @@ public:
 
 	bool setup();
 	void finalize();
-	void resetAndAssembleFrame(
-		std::function<void(void*)> onCqeReady);
-	void stop();
+
+	typedef std::function<void(void*, int)> resetAndAssembleFrameCbFn;
+	void resetAndAssembleFrame(resetAndAssembleFrameCbFn onCqeReady);
+	void stop(bool doAcquireLock = true);
+
+	typedef std::function<void(bool, AsynchronousLoop)> assembleFrameReqCbFn;
+	void assembleFrameReq(Callback<assembleFrameReqCbFn> cb);
 
 	// Telemetry helpers
 	static size_t computePointsPerDgram(int returnMode);
@@ -57,12 +65,19 @@ private:
 
 	// Stall detection timer
 	boost::asio::deadline_timer stallTimer;
-	// Callback for CQE notifications (called with user_data from each CQE)
-	std::function<void(void*)> onCqeReadyCallback;
+	// Callback for CQE ntfns (called with user_data+result from each CQE)
+	resetAndAssembleFrameCbFn onCqeReadyCallback;
+	// Flag to indicate assembly is in progress (cleared by stop())
+	// Protected by isAssemblingLock
+	SpinLock isAssemblingLock;
+	bool isAssembling;
 
 	void cancelIncompleteAndFillDummies();
 	void onEventfdRead(
 		const boost::system::error_code& error, std::size_t bytes_transferred);
+
+	class AssembleFrameReq;
+	friend class AssembleFrameReq;
 };
 
 } // namespace stim_buff

stimBuffApis/livoxGen1/livoxGen1.h

@@ -30,6 +30,8 @@ struct LivoxProto1DllState
 
 extern LivoxProto1DllState livoxProto1;
 
+extern const SmoCallbacks* smoHooksPtr;
+
 } // namespace stim_buff
 } // namespace smo
 

stimBuffApis/livoxGen1/pcloudStimulusBuffer.cpp

@@ -68,6 +68,16 @@ void PcloudStimulusBuffer::stop()
 
 void PcloudStimulusBuffer::stimFrameProductionTimesliceInd()
 {
+	ioUringAssemblyEngine.assembleFrameReq(
+		{nullptr, [this](bool success, AsynchronousLoop loop) {
+			if (!success) {
+				std::cerr << __func__ << ": Failed to assemble frame" << std::endl;
+			} else {
+				std::cout << __func__ << ": Successfully assembled frame "
+					<< loop.nSucceeded.load() << " slots succeeded "
+					<< "out of " << loop.nTotal << " total slots" << std::endl;
+			}
+		}});
 	// Release the spinlock for now
 	frameAssemblyRateLimiter.release();
 }