c++ - 使用仅在单个线程中调用的 io_service::run() 序列化 io_service::post() 执行

Question

如果我io_service::run()只在一个线程中运行，那么io_service::post()调用是在我要求它们执行的顺序相同，或者它们可以按任意顺序执行，我仍然需要使用 strand 来强制序列化执行？

Answer 1

这个问题之前已经处理过，例如

• Does boost::asio::io_service preserve the order of handlers? ？
• 文档:Oreder Of Handler Invocations

写的很清楚

if any of the following conditions are true:

• s.post(a) happens-before s.post(b)
• ...

then asio_handler_invoke(a1, &a1) happens-before asio_handler_invoke(b1, &b1).

请注意，单个 IO 线程会创建隐式链(文档)

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注意 关于另一个答案:当处理程序调用在异步操作完成时隐式完成时，当然这不成立。

Note that in the following case:

async_op_1(..., s.wrap(a));
async_op_2(..., s.wrap(b));

the completion of the first async operation will perform s.dispatch(a), and the second will perform s.dispatch(b), but the order in which those are performed is unspecified. That is, you cannot state whether one happens-before the other. Therefore none of the above conditions are met and no ordering guarantee is made.