设置 onmessage 处理程序时与网络工作者的竞争条件？

发布于 2024-09-09 06:56:32 字数 1439 浏览 9 评论 0原文

请考虑以下代码以及本 Mozilla 教程“使用 Web Worker” 中的说明：

var myWorker = new Worker('my_worker.js');
myWorker.onmessage = function(event) {
  print("Called back by the worker!\n");
};

本例中的第 1 行创建并开始运行工作线程。 第 2 行设置 onmessage 处理程序工人的功能是当worker调用自己的时候被调用 postMessage() 函数。

线程在调用 Worker 构造函数时启动。我想知道设置 onmessage 处理程序时是否可能存在竞争条件。例如，如果网络工作人员在设置 onmessage 之前发布一条消息。

有人对此了解更多吗？

更新：

Andrey 指出，网络工作者应该在收到消息时开始工作，就像 Mozilla 教程中的斐波那契示例一样。但这是否会在 Web Worker 中设置 onmessage 处理程序时产生新的竞争条件？

例如：

主脚本：

var myWorker = new Worker('worker.js');
myWorker.onmessage = function(evt) {..};
myWorker.postMessage('start');

Web Worker 脚本（'worker.js'）

var result = [];
onmessage = function(evt) {..};

然后考虑以下执行路径：

main thread                                  web worker
var worker = new Worker("worker.js");
                                             var result = [];
myWorker.onmessage = ..
myWorker.postMessage('start');
                                             onmessage = ..

“var result = []”行可以省略，它仍然会可以达到同样的效果。

这是一个有效的执行路径，我通过在网络工作者中设置超时来尝试它！目前我不明白如何使用网络工作者而不遇到竞争条件？！

原文

Please consider the following code and the explanation from this Mozilla tutorial "Using web workers":

var myWorker = new Worker('my_worker.js');
myWorker.onmessage = function(event) {
  print("Called back by the worker!\n");
};

Line 1 in this example creates and
starts running the worker thread.
Line 2 sets the onmessage handler for
the worker to a function that is
called when the worker calls its own
postMessage() function.

The thread is started in the moment the Worker constructor is called. I wonder if there might be a race-condition on setting the onmessage handler. For example if the web worker posts a message before onmessage is set.

Does someone know more about this?

Update:

Andrey pointed out that the web worker should start its work, when it receives a message, like in the Fibonacci example in the Mozilla tutorial. But doesn't that create a new race-condition on setting the onmessage handler in the web worker?

For example:

The main script:

var myWorker = new Worker('worker.js');
myWorker.onmessage = function(evt) {..};
myWorker.postMessage('start');

The web worker script ('worker.js')

var result = [];
onmessage = function(evt) {..};

And then consider the following execution path:

main thread                                  web worker
var worker = new Worker("worker.js");
                                             var result = [];
myWorker.onmessage = ..
myWorker.postMessage('start');
                                             onmessage = ..

The "var result = []" line can be left out, it will still be the same effect.

And this is a valid execution path, I tried it out by setting a timeout in the web worker! At the moment I can not see, how to use web workers without running into race-conditions?!

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