kotlin - 为什么协程首先在调用者线程上运行，但在第一个挂起点之后它在 “Dispatchers.Unconfined” 中的 DefaultExecutor 上运行？

Question

下面的代码打印

import kotlinx.coroutines.*

    fun main() = runBlocking<Unit> {
        launch(Dispatchers.Unconfined) {
            // not confined -- will work with main thread
            println("thread ${Thread.currentThread().name}")
            delay(500)
            println("thread ${Thread.currentThread().name}")
        }
    }

第一次在调用者线程上运行，但在第一个挂起点之后，它在“Dispatchers.Unconfined”中的 DefaultExecutor 上运行

 thread main
 thread kotlinx.coroutines.DefaultExecutor

Answer 1

阅读Dispatchers.Unconfined的描述，它准确地解释了这种行为:

A coroutine dispatcher that is not confined to any specific thread. It executes initial continuation of the coroutine immediately in the current call-frame and lets the coroutine resume in whatever thread that is used by the corresponding suspending function, without mandating any specific threading policy. Note: use with extreme caution, not for general code.