<https://pl.kotl.in/kbrTePWXD> the following runs into a deadlock(?) in kotlin 1.3.72; all the defa...

# coroutines

[vineethraj49]

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?

[vineethraj49]

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]

Looks like the code of a lazy delegate….

[vineethraj49]

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

[streetsofboston]

What happens if you decrease the concurrency value to 64 (or a bit less)?

[vineethraj49]

reducing concurrency works

[vineethraj49]

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

[vineethraj49]

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

[streetsofboston]

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…

[streetsofboston]

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]

that works ¯\_(ツ)_/¯

[vineethraj49]

but Obj init is a bit costly 😞

[wasyl]

What if you used a lazy Deferred instead?

[vineethraj49]

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

[vineethraj49]

which I can't

[wasyl]

From non-suspending context you could have a delegated by lazy { runBlocking { …. Just throwing ideas

[streetsofboston]

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]

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