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Fix a flaky check and a TSan violation in StateFlowStressTest. #4483

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merged 1 commit into from
Jul 31, 2025
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Fix a flaky check and a TSan violation in StateFlowStressTest. #4483

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30 changes: 16 additions & 14 deletions kotlinx-coroutines-core/jvm/test/flow/StateFlowStressTest.kt
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Original file line number Diff line number Diff line change
@@ -1,9 +1,10 @@
package kotlinx.coroutines.flow

import kotlinx.coroutines.testing.*
import java.util.concurrent.atomic.AtomicLongArray
import kotlin.random.*
import kotlinx.coroutines.*
import kotlinx.coroutines.testing.*
import org.junit.*
import kotlin.random.*

class StateFlowStressTest : TestBase() {
private val nSeconds = 3 * stressTestMultiplier
Expand All @@ -17,7 +18,7 @@ class StateFlowStressTest : TestBase() {

fun stress(nEmitters: Int, nCollectors: Int) = runTest {
pool = newFixedThreadPoolContext(nEmitters + nCollectors, "StateFlowStressTest")
val collected = Array(nCollectors) { LongArray(nEmitters) }
val collected = Array(nCollectors) { AtomicLongArray(nEmitters) }
val collectors = launch {
repeat(nCollectors) { collector ->
launch(pool) {
Expand All @@ -37,38 +38,39 @@ class StateFlowStressTest : TestBase() {
}
c[emitter] = current

}.take(batchSize).map { 1 }.sum()
}.take(batchSize).count()
} while (cnt == batchSize)
}
}
}
val emitted = LongArray(nEmitters)
val emitted = AtomicLongArray(nEmitters)
val emitters = launch {
repeat(nEmitters) { emitter ->
launch(pool) {
var current = 1L
while (true) {
state.value = current * nEmitters + emitter
emitted[emitter] = current
current++
if (current % 1000 == 0L) yield() // make it cancellable
state.value = emitted.incrementAndGet(emitter) * nEmitters + emitter
if (emitted[emitter] % 1000 == 0L) yield() // make it cancellable
}
}
}
}
for (second in 1..nSeconds) {
delay(1000)
val cs = collected.map { it.sum() }
println("$second: emitted=${emitted.sum()}, collected=${cs.minOrNull()}..${cs.maxOrNull()}")
println("$second: emitted=${emitted.sum()}, collected=${cs.min()}..${cs.max()}")
}
emitters.cancelAndJoin()
collectors.cancelAndJoin()
// make sure nothing hanged up
require(collected.all { c ->
c.withIndex().all { (emitter, current) -> current > emitted[emitter] / 2 }
})
for (i in 0..<nCollectors) {
check((0..<nEmitters).any { j -> collected[i][j] > emitted[j] * 0.9 }) {
"collector #$i failed to collect any of the most recently emitted values"
}
}
}

private fun AtomicLongArray.sum() = (0..<length()).sumOf(::get)

@Test
fun testSingleEmitterAndCollector() = stress(1, 1)

Expand Down