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/*
* Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
*/
package kotlinx.coroutines.selects
import kotlinx.coroutines.*
import kotlinx.coroutines.sync.*
import org.junit.*
import org.junit.Assert.*
class SelectPhilosophersStressTest : TestBase() {
private val TEST_DURATION = 3000L * stressTestMultiplier
val n = 10 // number of philosophers
private val forks = Array(n) { Mutex() }
private suspend fun eat(id: Int, desc: String) {
val left = forks[id]
val right = forks[(id + 1) % n]
while (true) {
val pair = selectUnbiased<Pair<Mutex, Mutex>> {
left.onLock(desc) { left to right }
right.onLock(desc) { right to left }
}
if (pair.second.tryLock(desc)) break
pair.first.unlock(desc)
pair.second.lock(desc)
if (pair.first.tryLock(desc)) break
pair.second.unlock(desc)
}
assertTrue(left.isLocked && right.isLocked)
// om, nom, nom --> eating!!!
right.unlock(desc)
left.unlock(desc)
}
@Test
fun testPhilosophers() = runBlocking<Unit> {
val timeLimit = System.currentTimeMillis() + TEST_DURATION
val philosophers = List<Deferred<Int>>(n) { id ->
async {
val desc = "Philosopher $id"
var eatsCount = 0
while (System.currentTimeMillis() < timeLimit) {
eat(id, desc)
eatsCount++
yield()
}
println("Philosopher $id done, eats $eatsCount times")
eatsCount
}
}
val debugJob = launch {
delay(3 * TEST_DURATION)
println("Test is failing. Lock states are:")
forks.withIndex().forEach { (id, mutex) -> println("$id: $mutex") }
}
val eats = withTimeout(5 * TEST_DURATION) { philosophers.map { it.await() } }
debugJob.cancel()
eats.withIndex().forEach { (id, eats) ->
assertTrue("$id shall not starve", eats > 0)
}
}
}
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