DefaultDispatcher-worker-xx thread state ：TIMED_WAITING (parking)

[yunipingan]

mutillevel coroutines and a lot of requests cause tomcat threads blocking, donnot know the reason, please give a solvment.

this is my code

    @GetMapping("/test")
    fun test() {
        runBlocking {
            println(Thread.currentThread().name)
            async(Dispatchers.Default) {
                println(Thread.currentThread().name)
                runBlocking() {
                    println(Thread.currentThread().name)
                    async(Dispatchers.Default) {
                        println(Thread.currentThread().name)
                    }
                }
            }
        }
    }

deploy and run tomcat , run a single request is normal, but run 10 concurrent requests, the tomcat is always waiting
this is output

http-nio-8866-exec-7
http-nio-8866-exec-2
http-nio-8866-exec-6
http-nio-8866-exec-1
http-nio-8866-exec-5
http-nio-8866-exec-10
http-nio-8866-exec-8
http-nio-8866-exec-9
http-nio-8866-exec-4
http-nio-8866-exec-3
DefaultDispatcher-worker-4
DefaultDispatcher-worker-2
DefaultDispatcher-worker-1
DefaultDispatcher-worker-3
DefaultDispatcher-worker-2
DefaultDispatcher-worker-4
DefaultDispatcher-worker-3
DefaultDispatcher-worker-1

jstack message

"DefaultDispatcher-worker-4" #39 daemon prio=5 os_prio=31 tid=0x00007fd4ca455000 nid=0x9803 waiting on condition [0x0000700009bff000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x0000000798a06340> (a kotlinx.coroutines.BlockingCoroutine)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:82)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:54)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:36)
	at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
	at com.example.web.DemoController$test3$1$1.invokeSuspend(DemoController.kt:98)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.access$runSafely(CoroutineScheduler.kt:60)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:740)

"DefaultDispatcher-worker-3" #38 daemon prio=5 os_prio=31 tid=0x00007fd4cb399800 nid=0x9a03 waiting on condition [0x0000700009afc000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x0000000798b45b60> (a kotlinx.coroutines.BlockingCoroutine)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:82)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:54)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:36)
	at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
	at com.example.web.DemoController$test3$1$1.invokeSuspend(DemoController.kt:98)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.access$runSafely(CoroutineScheduler.kt:60)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:740)

"DefaultDispatcher-worker-2" #37 daemon prio=5 os_prio=31 tid=0x00007fd4ca7e3800 nid=0x6703 waiting on condition [0x00007000099f9000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x00000007988b82e0> (a kotlinx.coroutines.BlockingCoroutine)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:82)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:54)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:36)
	at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
	at com.example.web.DemoController$test3$1$1.invokeSuspend(DemoController.kt:98)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.access$runSafely(CoroutineScheduler.kt:60)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:740)

"DefaultDispatcher-worker-1" #36 daemon prio=5 os_prio=31 tid=0x00007fd4cb389800 nid=0x6503 waiting on condition [0x00007000098f6000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x000000079877eb50> (a kotlinx.coroutines.BlockingCoroutine)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:82)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:54)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:36)
	at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
	at com.example.web.DemoController$test3$1$1.invokeSuspend(DemoController.kt:98)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.access$runSafely(CoroutineScheduler.kt:60)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:740)

[yunipingan]

kotlinx-coroutines-core version

<dependency>
    <groupId>org.jetbrains.kotlinx</groupId>
    <artifactId>kotlinx-coroutines-core</artifactId>
    <version>1.3.2-1.3.60</version>
</dependency>

[fvasco]

Do not use runBlocking inside a launch or async.
In this case the Dispatchers.Default is fully blocked.

Please read carefully the documentation
https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/run-blocking.html

[qwwdfsad]

@fvasco recommendation is correct, closing the issue

[fvasco]

As suggested by @qwwdfsad,
I copy-paste #1861

I found a trouble in the follow code:

import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking

object A {
    var ok = false

    init {
        println(1)
        runBlocking { }
        println(2)
        ok = true
        println(3)
    }

}

fun main() {
    runBlocking {
        launch { println(A.ok) }
        launch { println(A.ok) }
    }
}

I expect:

1
2
3
true
true

but it is:

1
false
2
3
true

openjdk version "11.0.6" 2020-01-14
kotlin 1.3.70
coroutine 1.3.4

Using GlobalScope.futute(Dispatchers.Unconfined) { }.get() is a workaround.

My use case does not result to a TIMED_WAITING or a deadlock, it works always but expose an object in an uninitialized state: ok cannot be false (second row in the response).

[iseki0]

Why it's not a bug? The runBlocking will be returned in future. @qwwdfsad