如果变量的值改变，则恢复程序 [英] Resume a program if variable's value changes

问题描述

有没有办法在 c / c ++ 暂停一个程序（可能与 SIGSTOP ），然后在另一个线程更改某个变量的值时继续（ SIGCONT ？）？

Is there a way in c/c++ to pause a program (might be with SIGSTOP), and then to continue (SIGCONT ?) it when another thread changes a value of some variable?

例如：

int main(void) {

    int a = 0;
    createThread(&a); //creates a thread which will change a's value

    pauseMyself(); //pauses main process till a's value is changed

    /* main process gets here only when a's value has been changed */

    fprintf(stderr, "a's value has been changed\n");

    return 0;
}

我想看看是否可能，所以我不需要抽样每个间隔 a 的值 - 像 while（）循环，它检查 a 的值每200ms（睡眠200ms）

I want to see if it is possible so I won't need to sample a's value each interval - Like a while() loop which checks a's value each 200ms (sleeps for 200ms)

这个问题的一个可能的解决方案是使用信号量：

One possible solution for this problem is using semaphores:

我应该将信号量初始化为 0 （！），
然后在 main（），而不是 pauseMyself（）我会做 sem_wait（），意味着主进程将停止

I should initialize semaphores value to 0 (!), Then in the main(), instead of pauseMyself() I'll do sem_wait(), means that the main process will stop there.

在线程函数中，我会在更改之后执行 sem_post（） 的价值，所以主要过程将继续。

In the thread function I'll do sem_post() after it changes a's value, so the main process will continue.

还有另一个更好的方法吗？

Is there another, nicer way?

谢谢。

推荐答案

我相信你需要的是 pthread条件变量，同步ation device：

I believe what you need is pthread condition variable, a synchronization device:

条件（条件变量的缩写）是同步设备，允许线程挂起执行并放弃处理器直到满足共享数据的一些谓词。条件的基本操作是：发出条件（当谓词变为真时），并等待条件，挂起线程执行，直到另一个线程发出条件。

A condition (short for ‘‘condition variable’’) is a synchronization device that allows threads to suspend execution and relinquish the processors until some predicate on shared data is satisfied. The basic operations on conditions are: signal the condition (when the predicate becomes true), and wait for the condition, suspending the thread execution until another thread signals the condition.

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