AQS获取锁过程

tail指向当前线程Node

head = new Node()tail = headnewNode为一个空节点(哨兵节点)

N

tail == null ? 

head指针指向当前Node

设置独占线程

shouldParkAfterFailedAcquire

Y

enq(node)

ReentrantLock获取锁过程

tail == null?

lock.lock()

node.predecessor() == head && tryAcquire

尝试获得锁?

NonFairLock.tryAcquire(1)

LockSupport.park()

acquire(1)

addWaiter()