Concurrent, non-blocking, lock-free queue and method, apparatus, and computer program product for implementing same

A dummy node is enqueued to a concurrent, non-blocking, lock-free FIFO queue only when necessary to prevent the queue from becoming empty. The dummy node is only enqueued during a dequeue operation and only when the queue contains a single user node during the dequeue operation. This reduces overhead relative to conventional mechanisms that always keep a dummy node in the queue. User nodes are enqueued directly to the queue and can be immediately dequeued on-demand by any thread. Preferably, the enqueueing and dequeueing operations include the use of load-linked/store conditional (LL/SC) synchronization primitives. This solves the ABA problem without requiring the use a unique number, such as a queue-specific number, and contrasts with conventional mechanisms that include the use of compare-and-swap (CAS) synchronization primitives and address the ABA problem through the use of a unique number. In addition, storage ordering fences are preferably inserted to allow the algorithm to run on weakly consistent processors.