ReentrantLock公平性参数(ReentrantLock fairness parameter)

 这个问题是完全理论化的，对不起，但这次我无法回避。 我正在学习ReentrantLock并阅读 ： 
 
 
 
 但请注意，锁的公平性并不能保证线程调度的公平性。 
 
 
 这是什么意思？ 我怎么能想象这个？ 
 
 我们假设现在没有人持有锁： 
 
 
 
 线程调度程序唤醒t1线程（谁不是最长的等待线程） 
 
 
 t1试图获得锁定 
 
 
 锁定拒绝t1因为t1不是最长的等待线程 
 
 
 t1进入睡眠状态 
 
 
 线程调度程序唤醒一个线程 
 
 
 Java是这样工作的吗？ 在一个非常不成功的情况下，这将意味着大量的上下文切换（导致吞吐量低，这在文档中写下）。 

This question is full theoretical, I'm sorry but I cannot avoid this time. I'm learning about ReentrantLock and read this:
 
 
 
Note however, that fairness of locks does not guarantee fairness of thread scheduling.
 
 
What does this mean? How can I imagine this? 
 
Let's suppose that the lock is not held by anyone right now:
 
 
 
thread scheduler wakes up t1 thread (who is not the longest waiting thread) 
 
 
t1 tries to acquire the lock
 
 
lock rejects t1 because t1 is not the longest waiting thread
 
 
t1 goes to sleep
 
 
thread scheduler wakes up a thread
 
 
Does Java work this way? In a very unsuccesful case this would mean lots of context switching (that leads to poor throughput, that is written down in the documentation).

原文：https://stackoverflow.com/questions/47473650