在Linux中等效的WaitForSingleObject和WaitForMultipleObjects? [英] WaitForSingleObject and WaitForMultipleObjects equivalent in Linux?

问题描述

我正在将应用程序从Windows迁移到Linux.我在WaitForSingleObject和WaitForMultipleObjects接口方面遇到问题.

I am migrating an applciation from windows to linux. I am facing problem with respect to WaitForSingleObject and WaitForMultipleObjects interfaces.

在我的应用程序中，我产生了多个线程，其中所有线程都等待父进程的事件或每t秒定期运行一次.

In my application I spawn multiple threads where all threads wait for events from parent process or periodically run for every t seconds.

我已经检查了pthread_cond_timedwait，但是我们必须为此指定绝对时间.

I have checked pthread_cond_timedwait, but we have to specify absolute time for this.

如何在Unix中实现呢?

How can I implement this in Unix?

推荐答案

粘贴到pthread_cond_timedwait并使用clock_gettime.例如:

struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
ts.tv_sec += 10; // ten seconds
while (!some_condition && ret == 0)
    ret = pthread_cond_timedwait(&cond, &mutex, &ts);

如果需要，可以将其包装在函数中.

Wrap it in a function if you wish.

更新:根据我们的评论对答案进行补充.

UPDATE: complementing the answer based on our comments.

POSIX没有像Windows那样的单一API来等待事件/对象的所有类型".每个人都有其自己的功能.通知线程终止的最简单方法是使用原子变量/操作.例如:

POSIX doesn't have a single API to wait for "all types" of events/objects as Windows does. Each one has its own functions. The simplest way to notify a thread for termination is using atomic variables/operations. For example:

主线程:

// Declare it globally (argh!) or pass by argument when the thread is created
atomic_t must_terminate = ATOMIC_INIT(0);

// "Signal" termination by changing the initial value
atomic_inc(&must_terminate); 

辅助线程:

// While it holds the default value
while (atomic_read(&must_terminate) == 0) {
    // Keep it running...
}
// Do proper cleanup, if needed
// Call pthread_exit() providing the exit status

另一种选择是使用pthread_cancel发送取消请求.被取消的线程必须已调用pthread_cleanup_push来注册任何必要的清除处理程序.这些处理程序以与注册时相反的顺序调用.切勿从清理处理程序中调用pthread_exit，因为它是未定义的行为.已取消线程的退出状态为PTHREAD_CANCELED.如果您选择这种替代方法，我建议您主要阅读有关取消点和类型的信息.

Another alternative is to send a cancellation request using pthread_cancel. The thread being cancelled must have called pthread_cleanup_push to register any necessary cleanup handler. These handlers are invoked in the reverse order they were registered. Never call pthread_exit from a cleanup handler, because it's undefined behaviour. The exit status of a cancelled thread is PTHREAD_CANCELED. If you opt for this alternative, I recommend you to read mainly about cancellation points and types.

最后但并非最不重要的一点是，调用pthread_join将使当前线程阻塞，直到由参数传递的线程终止.作为奖励，您将获得线程的退出状态.

And last but not least, calling pthread_join will make the current thread block until the thread passed by argument terminates. As bonus, you'll get the thread's exit status.

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