解锁流程源码

    public void unlock() {
        sync.release(1);
    }

    public final boolean release(int arg) {
        if (tryRelease(arg)) {
            Node h = head;
            //waitStatus =-1 表示自己有义务去唤醒别人
            if (h != null && h.waitStatus != 0)
                unparkSuccessor(h);
            return true;
        }
        return false;
    }

        protected final boolean tryRelease(int releases) {
            int c = getState() - releases;
            if (Thread.currentThread() != getExclusiveOwnerThread())
                //基本不会发生
                throw new IllegalMonitorStateException();
            boolean free = false;
            if (c == 0) {
                free = true;
                setExclusiveOwnerThread(null);
            }
            setState(c);
            return free;
        }

unparkSuccessor

    private void unparkSuccessor(Node node) {

        int ws = node.waitStatus;
        if (ws < 0)
            //将waitstatus由-1改成0，防止多线程情况下的访问导致需要额外唤醒别的线程
            com 

        Node s = node.next;
        //非正常情况 下一个节点被中断
        if (s == null || s.waitStatus > 0) {
            s = null;
            for (Node t = tail; t != null && t != node; t = t.prev)
                if (t.waitStatus <= 0)
                    s = t;
        }
         //正常情况
        if (s != null)
            LockSupport.unpark(s.thread);
    }