java线程池中为啥使用不可重入锁？

java线程池中为啥使用不可重入锁？

protected boolean tryAcquire(int unused) {
            if (compareAndSetState(0, 1)) {
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }****

https://www.cnblogs.com/theRhyme/p/9133804.html