1.6.0-native-mt broken with shareIn

[PaulWoitaschek]

The following example:

  @Test
  fun sharingTest() {
    runBlocking {
      flowOf(Unit).shareIn(GlobalScope, SharingStarted.WhileSubscribed())
        .collect { println(it) }
    }
  }

Throws an exception on native (tried on iosSimulatorArm64) using Kotlin 1.6.10 and coroutines 1.6.0. This was working fine with kotlin 1.5.2.

kotlin.IllegalStateException: Cannot start an undispatched coroutine in another thread DefaultDispatcher from current MainThread
kotlin.IllegalStateException: Cannot start an undispatched coroutine in another thread DefaultDispatcher from current MainThread
	at kotlin.Throwable#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Throwable.kt:24)
	at kotlin.Exception#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:23)
	at kotlin.RuntimeException#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:34)
	at kotlin.IllegalStateException#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:70)
	at kotlinx.coroutines.startCoroutine#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:136)
	at kotlinx.coroutines#startAbstractCoroutine(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:118)
	at kotlinx.coroutines.AbstractCoroutine#start(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/AbstractCoroutine.kt:130)
	at kotlinx.coroutines#launch__at__kotlinx.coroutines.CoroutineScope(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/Builders.common.kt:56)
	at kotlinx.coroutines.flow.launchSharing#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/flow/operators/Share.kt:209)
	at kotlinx.coroutines.flow#shareIn__at__kotlinx.coroutines.flow.Flow<0:0>(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/flow/operators/Share.kt:147)
	at kotlinx.coroutines.flow#shareIn$default__at__kotlinx.coroutines.flow.Flow<0:0>(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/flow/operators/Share.kt:135)
	at com.yazio.shared.common.property.FrozenPropertyTest.$sharingTest$lambda-1COROUTINE$0.invokeSuspend#internal(/Users/ph1b/repos/yazio/shared/common/src/commonTest/kotlin/com.yazio.shared.common.property/FrozenPropertyTest.kt:29)
	at kotlin.coroutines.native.internal.BaseContinuationImpl#resumeWith(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/coroutines/ContinuationImpl.kt:30)
	at kotlinx.coroutines.DispatchedTask#run(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Debug.kt:17)
	at kotlinx.coroutines.EventLoopImplBase#processNextEvent(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/EventLoop.common.kt:281)
	at kotlinx.coroutines#runEventLoop(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:87)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:74)
	at kotlinx.coroutines#runBlocking(/opt/buildAgent/work/6326934d18cfe24e/kotlin/libraries/stdlib/src/kotlin/contracts/ContractBuilder.kt:56)
	at kotlinx.coroutines#runBlocking$default(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:35)
	at com.yazio.shared.common.property.FrozenPropertyTest#sharingTest(/Users/ph1b/repos/yazio/shared/common/src/commonTest/kotlin/com.yazio.shared.common.property/FrozenPropertyTest.kt:28)
	at com.yazio.shared.common.property.$FrozenPropertyTest$test$0.$sharingTest$FUNCTION_REFERENCE$4.invoke#internal(/Users/ph1b/repos/yazio/shared/common/src/commonTest/kotlin/com.yazio.shared.common.property/FrozenPropertyTest.kt:27)
	at com.yazio.shared.common.property.$FrozenPropertyTest$test$0.$sharingTest$FUNCTION_REFERENCE$4.$<bridge-UNNN>invoke(/Users/ph1b/repos/yazio/shared/common/src/commonTest/kotlin/com.yazio.shared.common.property/FrozenPropertyTest.kt:27)
	at kotlin.native.internal.test.BaseClassSuite.TestCase#run(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/TestSuite.kt:85)
	at kotlin.native.internal.test.TestRunner.run#internal(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/TestRunner.kt:245)
	at kotlin.native.internal.test.TestRunner.runIteration#internal(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/TestRunner.kt:271)
	at kotlin.native.internal.test.TestRunner#run(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/TestRunner.kt:286)
	at kotlin.native.internal.test#testLauncherEntryPoint(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/Launcher.kt:30)
	at kotlin.native.internal.test#main(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/Launcher.kt:34)
	at <global>.Konan_start(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/Launcher.kt:33)

[petarmarijanovicfive]

Same here

[PaulWoitaschek]

Can we get a hotfix for this? This forces us to stay on 1.5

[qwwdfsad]

We're aiming to release 1.6.1 along with 1.6.1-native-mt next wekk

[PaulWoitaschek]

@qwwdfsad
Next week has passed, do you have any news on this?

[qwwdfsad]

Sorry for the delay, we had to postpone the release for now. Please stay tuned for the updates

[petarmarijanovicfive]

@qwwdfsad maybe an ETA for this? It pops up from time to time and we have to create some partial hotfixes because we are waiting for the fix in the new version

[qwwdfsad]

1.6.1-native-mt is out

[chippmann]

@qwwdfsad As of 1.6.3-native-mt this issue still exists if one enables the new memory manager:

    targets
        .filterIsInstance<org.jetbrains.kotlin.gradle.plugin.mpp.KotlinNativeTarget>()
        .forEach { kotlinNativeTarget ->
            with(kotlinNativeTarget) {
                binaries.all {
                        // enabling experimental memory model because ktor 2.x does not work otherwise on native atm: https://youtrack.jetbrains.com/issue/KTOR-4260/Ktor-client-Curl-engine-crash
                        binaryOptions["memoryModel"] = "experimental"
                        // because we need the new memory model for native targets because of the issue outlined above, we also want to enable the experimental concurrent mark and sweep gc to reduce gc pauses as much as possible
                        // see: https://kotlinlang.org/docs/whatsnew1620.html#concurrent-implementation-for-the-sweep-phase-in-new-memory-manager
                        freeCompilerArgs += "-Xgc=cms"

                        // better native stacktraces with libbacktrace: https://kotlinlang.org/docs/whatsnew1620.html#better-stack-traces-with-libbacktrace
                        // disadvantage: slightly slower link times; but the better output definitely makes up for it!
                        binaryOptions["sourceInfoType"] = "libbacktrace"
                }
            }
        }

Edit: I just realized that with the new memory manager, coroutines are multithreaded even without the native-mt version.
Sorry for the useless ping. But could you quickly confirm/deny my finding?

[LouisCAD]

Yup, and the new memory manager is becoming the default in 1.7.20 (there's an ongoing RC)

[petarmarijanovicfive]

@chippmann And yes, you don't need to use the native-mt version anymore 😁

[sigma-stochanskyi]

Working with 1.6.3-native-mt version on KMM. Facing same issue on iOS. Does someone else have this issue or is there any fix for that?

[LouisCAD]

Stop using the native-mt, not needed anymore with Kotlin 1.7.20+

[remcomokveld]

Would probably be good to update the documentation here then. Also it is now referring to a 1.6.4-native-mt which doesn't exist

[LouisCAD]

I bet you could get a doc updating PR accepted 🙂