如何在运行时替换线程应等待的WaitHandle [英] How to substitute at runtime the WaitHandle that a thread should wait on

问题描述

我想知道如何在运行时安全地更改线程应等待的EventWaitHandle.

I'm wondering how to safely change at runtime the EventWaitHandle that a thread should wait on.

例如，假设有两个线程(A和C)通过EventWaitHandles同步. A周期性地执行其工作，C一直等待，直到它从A接收到可以开始执行其工作的通知(例如通过AutoResetEvent).模式是A-C-A-C ...

Suppose for instance that there are two threads (A and C) that are synchronized through EventWaitHandles. A does its job cyclically and C waits until it receives notification from A that it can start doing its job (e.g. by the AutoResetEvent). The pattern is A-C-A-C...

稍后在新线程(B)上启动(例如，通过用户操作)，并且应以这种方式在两个预先存在的线程之间执行其作业:A进行其作业，然后发出信号B，一旦B完成，则发出信号C .现在的模式是ABCABC ...

Later on a new thread (B) is launched (e.g. by user action) and its job should be executed in between the two preexistent threads in this way: A makes its job, then signals B and once B finishes it signals C. Now the pattern is A-B-C-A-B-C...

因此，在线程C等待与A共享的EventWaitHandle之后，应该有一个安全的机制使C等待与B共享的另一个EventWaitHandle.在我看来，棘手的部分是替换C使用的EventWaitHandle，因为一旦完成，我应该很容易就能启动B，它将使用EventWaitHandle等待A作业，并使用EventWaitHandle发出信号通知C作业.该机制还应该提供一种安全卸载线程B的方法，并返回到只有线程A和C在工作的初始状态.

So before thread C was waiting on the EventWaitHandle shared with A and later there should be a safe mechanism that makes C waiting on another EventWaitHandle shared with B. It seems to me that the tricky part is substituting the EventWaitHandle used by C, since once this is done I should easily be able to launch B that will use a EventWaitHandle to wait on A job and a EventWaitHandle to signal for C job. The mechanism should also provide a way to safely unmount thread B and to go back to the initial situation where only thread A and C are working.

是否存在使用EventWaitHandle完成此操作的安全方法?如果没有，将不胜感激.

Is there a safe way to accomplish this with EventWaitHandle ? If not, any other suggestion would be appreciated.

推荐答案

如果任务A知道更改，则让任务C拥有该事件.如果下一个任务C，则任务A发出任务C的事件信号；如果下一个任务B，则任务B发出信号.

If task A knows about the change, then have task C own the event. Task A signals task C's event if C is to be next, or task B's event if task B is to be next.

或者，使用与更改任何其他共享数据相同的机制:在对句柄的所有访问中获取互斥量.例如任务C获取锁，读取句柄，释放锁，等待句柄.要对其进行更改，您需要让UI线程获取该锁，更改该句柄，然后释放该锁.

Alternatively, use the same mechanism as for changing any other shared data: acquire a mutex across all accesses to the handle. e.g. task C acquires the lock, reads the handle, releases the lock, waits on the handle. To change it you have the UI thread acquire the lock, change the handle, release the lock.

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