如何使用暂停然后恢复或替代方法在线程之间同步共享数据 [英] How to synchronize shared data between threads by using pause then resume or alternatives
问题描述
我正在编写一个游戏，其中一个线程 - GameThread - 永远循环，更新我的所有精灵，渲染它们，然后在再次执行之前休眠一段时间.我还有一个定制的事件处理程序，用于处理按键等.
I'm writing a game in which a thread - GameThread - loops forever, updating all my sprites, rendering them, and then sleeping for some time before doing it all again. I also have a custom-made Event handler which deals with key presses etc.
这在大多数情况下都可以正常工作.但是，如果在渲染 GameThread 时抛出事件，我会遇到问题.在极少数情况下，处理事件的处理程序可能会同时更改需要呈现的内容，从而影响 GameThread 呈现的结果.
This all works fine in most cases. However I have a problem if an event is thrown while GameThread is rendering. On rare occasions, the handler that deals with the event may make a concurrent change to what needs to be rendered affecting the results of the GameThread rendering.
为了避免这种情况，我希望事件处理程序立即暂停 GameThread，处理事件，然后恢复 GameThread.
To avoid this, I want the event handler to pause the GameThread immediately, handle the event, then resume GameThread.
suspend()/resume()方法适合我的需要，但它们已被弃用.但是，在我的情况下，由于死锁的可能性很小，无论如何使用它们是否安全?
The
suspend()/resume()methods suit my needs, but they were deprecated. In my case, however, as there is little chance of a deadlock, is it safe to use them regardless?
如果没有，我还有哪些其他没有大量开销的替代方案?
If no, what other alternatives do I have that don't have a huge amount of overhead?
我看到了通过在要暂停的线程中设置标志来请求线程暂停的建议.然而，就我而言，我认为这不是一个可行的选择，因为 GameThread 循环在循环迭代期间可能需要一段时间.在我完成循环之前，我将无法检查标志，然后为时已晚.
I have seen a suggestion of requesting a thread to pause by setting a flag in the Thread to be paused. In my case, however, I don't see that as a viable option since the GameThread loop may take a while during an iteration through the loop. I won't be able to check the flag until I'm done with the loop and by then it is too late.
我需要立即暂停，否则用户会注意到事件处理有延迟.
I need immediate pausing, or else the user will notice a delay in the event handling.
推荐答案
suspend()/resume() 方法适合我的需要，但它们已被弃用.但是，在我的情况下，由于发生僵局的可能性很小，无论如何使用它们是否安全?
The suspend() / resume() methods suit my needs, but they were deprecated. In my case, however, as there is little chance of a deadlock, is it safe to use them regardless?
显然，如果死锁的可能性为零，那么它是安全的.但是有各种意想不到的方法会导致僵局.例如，您可能在初始化一个类时碰巧暂停了一个线程……这将使任何其他试图引用该类的静态字段的线程死锁.(这是 JVM 特定行为的结果.还有其他地方没有指定在引擎盖下进行的锁定/同步.很公平.它不需要......除非你正在考虑使用这些已弃用的方法.)
Obviously, if there is ZERO chance of a deadlock then it is safe. But there are all sorts of unexpected ways to get a deadlock. For instance, you could happen to pause a thread while it is initializing a class ... and that would deadlock any other thread trying to refer to a static field of that class. (This is a consequence of a specified behaviour of the JVM. There are other places where the locking / synchronization that goes on under the hood is not specified. Fair enough. It doesn't need to be ... unless you are contemplating using these deprecated methods.)
所以，现实是很难确定(证明)它是否真的安全.如果你不能确定这一点，那么这是一件有潜在风险的事情.这就是不推荐使用这些方法的原因.
So, the reality is that it is really difficult to determine (prove) if it is actually safe. And if you can't determine this, then it is a potentially risky thing to do. That's WHY the methods are deprecated.
(严格来说，这不是死锁.死锁是指线程永远无法继续执行.在这种情况下，如果您可以恢复暂停的线程，其他线程可以继续执行.)
(Strictly speaking, this is not a deadlock. A deadlock is when the threads can never proceed. In this case, the other threads can proceed if you can resume the paused thread.)
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