Recently implemented a fixed-size memory pool with spinlocks and now I'm wondering - how would one implement them without a spinlock? Edit: Maybe I'm confusing

Recently implemented a fixed-size memory pool with spinlocks and now I'm wondering - how would one implement them without a spinlock? Edit: Maybe I'm confusing terminology. What I'm doing is looping until other threads returned memory, but I'm also doing a short sleep during each loop iteration.