What does `Dispatchers Unconfined` do if it ever needs to di kotlinlang #coroutines

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

06/01/2021, 6:18 PM

you're running synchronously in the call to

continuation.resume()

from whatever caused it to be resumed

mbonnin

06/01/2021, 6:20 PM

But what thread is going to call

continuation.resume()

after the 10ms delay?

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

06/01/2021, 6:24 PM

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

👍 1

mbonnin

06/01/2021, 6:24 PM

Actually, I can reduce the snippet to

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

Yep,

Default

is what I'm observing

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

Adam Powell

06/01/2021, 6:25 PM

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

Dispatchers.Unconfined

🙂

👍 1

mbonnin

06/01/2021, 6:26 PM

Yea, looks like it 🙂

Thanks for the pointers!

👍 1

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