• <div><p>I opened this gcode test of 97 million lines to be tested,wait a long time to prepare. http://www.picengrave.com/downloads/darklylabs/Roy%20Rogers%20Metric.zip</p> <p>When I use the latest ...
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  • Long wait time for response

    2020-11-22 13:58:55
    <img alt="image" src="https://img-blog.csdnimg.cn/img_convert/c5ce980baf84455d562d8e7375aed979.png" /></li></ul> <p>Since I upgraded to 1.3.0 I must always wait for over 1 minute for the login-window:...
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  • <div><p><strong>Describe the ...3. wait for eternity <p><strong>Expected behavior If the resolver is not reachable there should be no retries.</p><p>该提问来源于开源项目:heimdal/heimdal</p></div>
  • 在很多讲 waitlong timeout)的例子,都会用下面类似的代码: public class RunA implements Runnable { private Object lock; public RunA(Object lock) { this.lock = lock; } @Override public void run() {...

    在很多讲 wait(long timeout)的例子,都会用下面类似的代码:

    public class RunA implements Runnable {
        private Object lock;
        public RunA(Object lock) {
            this.lock = lock;
       public void run() {
          synchronized (lock){
              try  {
                   System.out.println("A begin----");
    //               lock.wait(); // 永远等待着,不会执行下去【处在等待队列】
    //               lock.wait(0); // 永远等待着,不会执行下去【处在等待队列】
                     lock.wait(2000);// 等待了 2 秒之后,继续执行下去【锁池队列,抢监视器锁】
                  System.out.println("A end----");
              } catch (InterruptedException e) {

    举这样的例子显然是没有任何意义的,在这里用 wait(2000)和 sleep(2000) 有什么区别呢?

    wait 和 sleep 显然是有很大的区别,但区别不只是 wait 会把 lock 释放掉,然我们引入一个新的搅和线程 B

    public class RunB implements Runnable {
        private Object lock;
        public RunB(Object lock) {
            this.lock = lock;
      public void run() {
            synchronized (lock) {
                System.out.println("b come----");
                while (true) {

    B 仅仅是握住锁,然后永远不释放,然后回到我们的主舞台 main 函数:

    public static void main(String[] args) throws InterruptedException {
        Object lock = new Object();
        Thread threadA = new Thread(new RunA(lock));
        Thread threadB = new Thread(new RunB(lock));

    然后再 run 一下,发现 A end ying 永远不会打印了,咦,为啥 wait(2000)之后没有被唤醒执行下去了呢?

    仔细想想 A 显示获得了锁,然后 wait(2000)交出了锁,然后 B 拿到了锁,这个时候过了 2 秒,A 确实是被唤醒了,但很可惜 A 永远也不会得到锁了对于临界区永远只能有一个线程在执行,不可能出现两个临界区同时在执行代码的可能,所以被唤醒之后,还需要去争抢锁,并不是唤醒了就能继续执行代码的


    其它的线程调用 obj.notify(),且当前线程 T,正好是被选中唤醒的。

    其它的线程调用 obj.notifyAll()。

    其它线程中断 T。



    大多数时候我们忽略唤醒之后需要去抢到临界区的锁,是因为 notify 用的多的关系,触发 notify 的线程必然有锁,只会唤醒一个线程,所以被唤醒的线程必然得到锁!于是大家就会产生一个被唤醒一定能执行点的错觉

    而我觉得很多文章没有指明这一点,然当你意识到了这个之后,对 notifyAll 就也不会有一起全部唤醒执行的想当然理解了,notifyAll 只是让大家都去抢临界区,所有的 wait notify,都是为了保护临界区永远只能有一个在执行,分析问题还是从源头入手,见笑。。

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  • 并发编程小知识 object.wait 和 object.wait(long timeout) 通常的理解 相同点: 都会在拥有锁的时候立即释放锁,线程会被系统挂起,失去cpu时间片,得不到调度。 不同点: 后者线程会在指定timeout的时间过去之后被...

    并发编程小知识 object.wait 和 object.wait(long timeout)




    Q: 后者是在timeout的时间之后从wait立即返回吗
    A: 答案是NO, timeout时间只是线程被阻塞的时间,过了这个时间,线程会被重新唤醒,并且去争夺锁。但并不意味着此时线程能从这个方法返回。如果线程没有获得锁依然会放在锁的等待队列里面。所以当前线程依然在这个方法里面等待获取锁,那么只有当从wait方法返回的时候,才是获得到了锁,当然这里没考虑线程被中断的情况。
    所以线程被唤醒 != 线程得到锁。
    在学些Java的并发框架是,理解这点尤其重要。如ReentrantLock的Condition,他的await和await(long timeout)语义上是和object的两个方法是一样的。最简单的理解就是当线程从这两个方法返回的时候,才是一定获得了锁。(这里不考虑中断)

  • m accustomed to publishing taking a few millis on a local broker (Mosquitto), but this simple code needs 1000ms: <pre><code>rust let client_options = MqttOptions::new() .set_client_id("...
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  • Current behavior: When clicking Start to start the server, I must wait a minimum of 5 minutes (sometimes longer, up to 20 minutes) before the server starts. Steps to reproduce: Start the server, and ...
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  • <p>Should probably be in a go routine and reply at the end of the go routine, otoh the long delete means no Request() will tend to wait that long for a response either</p><p>该提问来源于开源项目ÿ...
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  • But what I experience is that the Cloudformation resource takes a long time before it reaches the complete state. Attached is a cloudwatch log when the create has finished: <p><img alt="image" src=...



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