- harzard pointer:
- The array-based hp in userspace.
 
 
- locked rcu:
- The user space rcu with global reference count.
 
 - classic rcu:
- The kernel space rcu with preemptible kernel.
 - Support sparse checking.
 
 - thrd-based rcu:
- The user space rcu with thread-local-storage reference count.
 - Implement concurrency linked-list.
 - Support sparse checking.
 
 
- seqlock:
- The linux kernel style userspace seqlock.
 
 
- ref:
- The cache friendly concurrency skiplist in the kernel space. It is from Liu Bo and Fusion-io.
 
 - src:
- The sequential program skiplist in userspace.