A system includes, in a first memory location, a pointer to a next one of the plurality of memory locations and a respective reference counter, in each of respective ones of a plurality of memory locations, a pointer to a next one of the plurality of memory locations, a pointer to a previous one of the plurality of memory locations, and a reference counter, and in a last memory location, a pointer to a previous one of the plurality of memory locations and a respective reference counter, and atomically incrementing and decrementing of a reference counter stored in one of the plurality of memory locations.