What does `Dispatchers.Unconfined` do if it ever ...

# coroutines

[mbonnin]

What does Dispatchers.Unconfined do if it ever needs to dispatch ?

runBlocking {
      withContext(Dispatchers.Unconfined) {
        withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
          // do something in IO here
        }
        // I am still in an IO thread
        delay(10) // dispatch
        // what thread am I here?
      }
    }

[Adam Powell]

you're running synchronously in the call to continuation.resume() from whatever caused it to be resumed

[mbonnin]

But what thread is going to call continuation.resume() after the 10ms delay?

[mbonnin]

I get the withContext(<http://Dispatchers.IO|Dispatchers.IO>) {} calls me back in IO context. But the delay , I'm not sure how it's going to resume. I would somehow expect to fallback to the dispatcher from the initial runBlocking but that doesn't seem to be the case.

[Adam Powell]

probably this: https://github.com/Kotlin/kotlinx.coroutines/blob/master/kotlinx-coroutines-core/jvm/src/DefaultExecutor.kt#L10

[mbonnin]

Actually, I can reduce the snippet to

runBlocking {
      withContext(Dispatchers.Unconfined) {
        delay(10) // dispatch
        // what thread am I here?
      }
    }

[mbonnin]

Yep, Default is what I'm observing

[mbonnin]

Just not sure if that's a thing I should be relying on or if it's in the "dangerous" zone...

[Adam Powell]

basically if you're asking this question for anything other than idle curiosity you probably don't want to be using Dispatchers.Unconfined 🙂

[mbonnin]

Yea, looks like it 🙂

[mbonnin]

Thanks for the pointers!