Locking:Qutex: Skeleton for Qutex class

include/qutex.h

@@ -0,0 +1,139 @@
+#ifndef QUTEX_H
+#define QUTEX_H
+
+#include <list>
+#include <atomic>
+#include <memory>
+#include <spinLock.h>
+
+namespace smo {
+
+// Forward declarations
+class LockerAndInvoker;
+
+/**
+ * @brief Qutex - Queue-based mutex for asynchronous lock management
+ *
+ * A Qutex combines a spinlock, an ownership flag, and a queue of waiting
+ * lockvokers to provide efficient asynchronous lock management with
+ * priority-based acquisition for LockSets.
+ */
+class Qutex
+{
+public:
+	typedef std::list<std::shared_ptr<LockerAndInvoker>> LockerAndInvokerList;
+
+	/**
+	 * @brief Constructor
+	 */
+	Qutex()
+	{
+		// TODO: Initialize member variables
+	}
+
+	/**
+	 * @brief Register a lockvoker in the queue
+	 * @param lockvoker The lockvoker to register
+	 * @return Iterator pointing to the registered lockvoker in the queue
+	 */
+	LockerAndInvokerList::iterator registerInQueue(
+		const std::shared_ptr<LockerAndInvoker> &lockvoker
+		)
+	{
+		// TODO: Implement registration logic
+		// - Acquire the spinlock
+		// - Insert lockvoker at the rear of the queue
+		// - Return iterator to the inserted element
+		// - Release the spinlock
+		lock.acquire();
+		auto it = queue.insert(queue.end(), lockvoker);
+		lock.release();
+		return it;
+	}
+
+	/**
+	 * @brief Unregister a lockvoker from the queue
+	 * @param it Iterator pointing to the lockvoker to unregister
+	 */
+	void unregisterFromQueue(LockerAndInvokerList::iterator it)
+	{
+		// TODO: Implement unregistration logic
+		// - Acquire the spinlock
+		// - Erase the element at the given iterator
+		// - Release the spinlock
+		(void)it;  // Suppress unused parameter warning
+	}
+
+	/**
+	 * @brief Try to acquire the lock for a lockvoker
+	 * @param tryingLockvoker The lockvoker attempting to acquire the lock
+	 * @param nRequiredLocks Number of locks required by the lockvoker's LockSet
+	 * @return true if the lock was successfully acquired, false otherwise
+	 */
+	bool tryAcquire(LockerAndInvoker &tryingLockvoker, int nRequiredLocks)
+	{
+		// TODO: Implement acquisition logic
+		// - Acquire the spinlock
+		// - Check if lock is already owned
+		// - For single-lock requests, grant immediately if available
+		// - For multi-lock requests, check if in top X% of queue
+		// - Set isOwned flag if successful
+		// - Release the spinlock
+		// - Return success/failure
+		(void)tryingLockvoker;  // Suppress unused parameter warning
+		(void)nRequiredLocks;   // Suppress unused parameter warning
+		return false;  // Placeholder return value
+	}
+
+	/**
+	 * @brief Handle backoff when a lockvoker fails to acquire all required locks
+	 * @param failedAcquirer The lockvoker that failed to acquire all locks
+	 */
+	void backoff(LockerAndInvoker &failedAcquirer)
+	{
+		// TODO: Implement backoff logic
+		// - Acquire the spinlock
+		// - If failedAcquirer is at front, rotate queue items
+		// - Move failedAcquirer to appropriate position in queue
+		// - Release the spinlock
+		// - Wake up the new front item
+		(void)failedAcquirer;  // Suppress unused parameter warning
+	}
+
+	/**
+	 * @brief Release the lock and wake up the next waiting lockvoker
+	 * @param prevOwner The lockvoker that previously owned the lock
+	 */
+	void release(LockerAndInvoker &prevOwner)
+	{
+		// TODO: Implement release logic
+		// - Acquire the spinlock
+		// - Unregister the previous owner from the queue
+		// - Clear the isOwned flag
+		// - Get the new front item
+		// - Release the spinlock
+		// - Wake up the new front item (conditionally)
+		(void)prevOwner;  // Suppress unused parameter warning
+	}
+
+	/**
+	 * @brief Wake up a specific lockvoker
+	 * @param lockvoker The lockvoker to wake up
+	 */
+	void wakeUp(LockerAndInvoker &lockvoker)
+	{
+		// TODO: Implement wake-up logic
+		// - Post the lockvoker's invocation to its io_service
+		// - This will cause the lockvoker to retry acquisition
+		(void)lockvoker;  // Suppress unused parameter warning
+	}
+
+public:
+	SpinLock lock;
+	std::atomic<bool> isOwned;
+	LockerAndInvokerList queue;
+};
+
+} // namespace smo
+
+#endif // QUTEX_H