<https pl kotl in kbrTePWXD> the following runs into a deadl kotlinlang #coroutines

https://pl.kotl.in/kbrTePWXD the following runs into a deadlock(?) in kotlin 1.3.72; all the default dispatcher worker threads are in a MONITOR state 🤔 can someone point me in the direction to figuring this out?

return synchronized(lock) {

val _v2 = _value

if (_v2 !== UNINITIALIZED_VALUE) {

@Suppress("UNCHECKED_CAST") (_v2 as T)

} else {

val typedValue = initializer!!() <-- gets till this invocation and then blocked

_value = typedValue

initializer = null

typedValue

streetsofboston

08/14/2020, 1:32 PM

Looks like the code of a

lazy

delegate….

vineethraj49

08/14/2020, 1:33 PM

yes, i was setting a debug point to see how far it got

streetsofboston

08/14/2020, 1:35 PM

What happens if you decrease the

concurrency

value to 64 (or a bit less)?

vineethraj49

08/14/2020, 1:35 PM

reducing concurrency works

whatever kotlin version play.kotlinlang is on, also works regardless of concurrency

so I'm assuming there's a workaround for 1.3.72 🤞

streetsofboston

08/14/2020, 1:36 PM

I have such a nagging feeling that all (at least 64 of them) the asyncs (the 128 of them) are executing and suspending. Then a blocking

lazy{ .. }

is executed for the

lz

variable that can’t finish, since there are no threads left to run that

test

function…

If the many

async

were to be scheduled in a bit more sequential fashion, not all 64 IO threads would be unavailable? What happens if you don’t make

lz

lazy, but just

val lz = Obj()

vineethraj49

08/14/2020, 1:42 PM

that works ¯\_(ツ)_/¯

but Obj init is a bit costly 😞

wasyl

08/14/2020, 1:50 PM

What if you used a lazy

Deferred

instead?

vineethraj49

08/14/2020, 1:51 PM

then I'll have to change a bunch of legacy code to be suspend so I can do a .await

👍 1

which I can't

wasyl

08/14/2020, 1:53 PM

From non-suspending context you could have a delegated

by lazy { runBlocking { …

. Just throwing ideas

streetsofboston

08/14/2020, 2:08 PM

Couldn’t you move

val lz = Obj()

as the first statement in the GlobalScope.launch?

GlobalScope.launch {
    val lz = with(<http://Dispatchers.IO|Dispatchers.IO>) { Obj() } // use IO, since creation of Obj() is blocking
    val concurrency = 128
    ...
}

vineethraj49

08/14/2020, 2:15 PM

I figure this is happening because Dispatchers.IO is "full" (64 already running) and another withContext/runBlocking(Dispatchers.IO) cannot start up but why does the same code work on 1.4

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