Glassthought

Example Race Condition

1 min read

With Threads

Race condition With Threads

package com.glassthought.sandbox
 
class RaceConditionInducer {
  private var value = 0
 
  
  // @Synchronized // would fix this example race condition.
  fun incrementValue() {
    val storedValue = value
 
    Thread.sleep(10)
 
    println("Incrementing value from storedValue=$storedValue to ${storedValue + 1}")
    value = storedValue + 1
  }
 
  fun getValue() = value
}
 
fun main() {
  val raceConditionInducer = RaceConditionInducer()
 
  val threads = (1..10).map {
    Thread { raceConditionInducer.incrementValue() }
  }
  threads.forEach { it.start() }
  threads.forEach { it.join() }
 
  println("Value: ${raceConditionInducer.getValue()}")
}

Command to reproduce:

gt.sandbox.checkout.commit 0b65495f3299ff186efc \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew run"

Recorded output of command:

> Task :app:checkKotlinGradlePluginConfigurationErrors SKIPPED
> Task :app:processResources NO-SOURCE
> Task :app:compileKotlin
> Task :app:compileJava NO-SOURCE
> Task :app:classes UP-TO-DATE
 
> Task :app:run
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Value: 1
 
BUILD SUCCESSFUL in 1s
2 actionable tasks: 2 executed
Link to original

With CoRoutines

Race Condition With Coroutines

package com.glassthought.sandbox
 
import kotlinx.coroutines.*
import kotlin.random.Random
 
class RaceConditionInducer {
  private var value = 0
 
  // Suspending function to simulate some work and induce a race condition
  suspend fun incrementValue() {
    val storedValue = value
 
    // Simulate delay to increase the likelihood of race conditions
    delay(10)
 
    println("Incrementing value from storedValue=$storedValue to ${storedValue + 1}")
    value = storedValue + 1
  }
 
  fun getValue() = value
}
 
fun main() = runBlocking {
  val raceConditionInducer = RaceConditionInducer()
 
  // Launch multiple coroutines to increment the value
  val jobs = List(10) {
    GlobalScope.launch {
      raceConditionInducer.incrementValue()
    }
  }
 
  // Wait for all coroutines to complete
  jobs.forEach { it.join() }
 
  println("Final Value: ${raceConditionInducer.getValue()}")
}

Command to reproduce:

gt.sandbox.checkout.commit a82a70441214360361c9 \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew run"

Recorded output of command:

> Task :app:checkKotlinGradlePluginConfigurationErrors SKIPPED
> Task :app:compileKotlin UP-TO-DATE
> Task :app:compileJava NO-SOURCE
> Task :app:processResources NO-SOURCE
> Task :app:classes UP-TO-DATE
 
> Task :app:run
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Incrementing value from storedValue=0 to 1
Final Value: 1
 
BUILD SUCCESSFUL in 704ms
2 actionable tasks: 1 executed, 1 up-to-date
Link to original

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