I have: ```private suspend fun awaitX(arg1: String): X? = suspendCancellableCoroutine { functio...

# coroutines

[Wai-Wai Ng]

I have:

private suspend fun awaitX(arg1: String): X? = suspendCancellableCoroutine { 
    functionThatExecutesCallback{ result -> println("test"); it.resume(result) }
}

and for some reason, the function that calls this never resumes execution even though test does get printed. Any obvious ideas as to what to check? IntelliJ isn't showing the Coroutine debugger tab so I'm somewhat limited to debugging by printing...

[Zach Klippenstein (he/him) [MOD]]

Is the job cancelled for some reason before you resume? Which dispatcher are you using?

[Wai-Wai Ng]

No, definitely not cancelled. Dispatcher is Dispatchers.IO

[Zach Klippenstein (he/him) [MOD]]

Any chance the IO pool is saturated? Just throwing out guesses. I would probably start debugging into the coroutines code itself at this point

[Wai-Wai Ng]

It turns out the issue was a runBlocking inside functionThatExecutesCallback that launched a separate coroutine that never finished. I'm not sure this is strictly intuitive behaviour but at the same time I'm not persuaded it's definitely wrong.

[Zach Klippenstein (he/him) [MOD]]

This is why runBlocking is generally considered Very Bad. One perfectly innocent little use and suddenly you’ve got a deadlock in code a mile away