http://blog.csdn.net/dog250/article/details/5303424
##pre-ergo
There a lot of subsytem, code segments use RCU in their implement.
It's really need to know the truth of RCU before understanding linux kernel.
##history of RCU
old fasion rcu
premtiable rcu
tree-rcu
##Design pattern
In this article, the paragraph RCV OVERVIEW is the very clearly explaination of RCU. You should understand, I think, a grace period is start at removing the old data(maybe leading by rcu_assign_pointer) !!!
##WFF
##FAQ
In classical RCU, if the entry will be deleted has a previous pointer?
RCU callback function
