Concurrency Coordination Reports

Atomic Guard Coordination Report

Record nonblocking one-shot guard acquisitions and report whether a later attempt was blocked.

compare-and-set guard A coordination report records nonblocking acquire attempts. An `java.util.concurrent.atomic.AtomicBoolean` started at false models an exclusive one-shot guard, and `compareAndSet(false, true)` returns true only for the attempt that flips the flag, so it never blocks. The first acquire flips the flag, so a later attempt in the same run reads true and is reported as blocked. The status line summarizes whether the section stayed idle, guarded, or blocked a later acquire.

Atomic Guard Coordination Report

holds
AtomicGuardCoordinationReport.kt
Replay: real traced execution (multi-file project)
import java.util.concurrent.atomic.AtomicBoolean

fun main() {
    val holds = 1
    val guard = AtomicBoolean(false)
    var acquired = 0
    var blocked = 0

    for (i in 0 until holds) {
        if (guard.compareAndSet(false, true)) {
            acquired++
        } else {
            blocked++
        }
    }

    val status = if (acquired == 0) {
        "idle"
    } else if (blocked > 0) {
        "blocked"
    } else {
        "guarded"
    }

    println("holds=$holds acquired=$acquired blocked=$blocked $status")
}

import java.util.concurrent.atomic.AtomicBoolean

fun main() {
    val holds = 0
    val guard = AtomicBoolean(false)
    var acquired = 0
    var blocked = 0

    for (i in 0 until holds) {
        if (guard.compareAndSet(false, true)) {
            acquired++
        } else {
            blocked++
        }
    }

    val status = if (acquired == 0) {
        "idle"
    } else if (blocked > 0) {
        "blocked"
    } else {
        "guarded"
    }

    println("holds=$holds acquired=$acquired blocked=$blocked $status")
}

import java.util.concurrent.atomic.AtomicBoolean

fun main() {
    val holds = 2
    val guard = AtomicBoolean(false)
    var acquired = 0
    var blocked = 0

    for (i in 0 until holds) {
        if (guard.compareAndSet(false, true)) {
            acquired++
        } else {
            blocked++
        }
    }

    val status = if (acquired == 0) {
        "idle"
    } else if (blocked > 0) {
        "blocked"
    } else {
        "guarded"
    }

    println("holds=$holds acquired=$acquired blocked=$blocked $status")
}

  1. holds ← 1, guard ← false, acquired ← 0, blocked ← 0

    3fun main() {4    val holds→ 1 = 1 //@holds=0, 25    val guard→ false = AtomicBoolean(false)6    var acquired→ 0 = 07    var blocked→ 0 = 0

  2. for (i in 0 until holds)

    9for (i0 in 0 until holds1) {10    if (guard.compareAndSet(false, true)) {

  3. if (guard.compareAndSet(false, true))

    9for (i in 0 until holds) {10    if (guardtrue.compareAndSet(false, true)) {11        acquired0++12    } else {13        blocked++

  4. status ← guarded

    17    val status→ guarded = if (acquired1 == 0) {18        "idle"19    } else if (blocked0 > 0) {20        "blocked"21    } else {22        "guarded"23    }2425    println("holds=$holds1 acquired=$acquired1 blocked=$blocked0 $statusguarded")26}
    outputholds=1 acquired=1 blocked=0 guarded

  1. holds ← 0, guard ← false, acquired ← 0, blocked ← 0, status ← idle

    3fun main() {4    val holds→ 0 = 05    val guard→ false = AtomicBoolean(false)6    var acquired→ 0 = 07    var blocked→ 0 = 089    for (i in 0 until holds) {10        if (guard.compareAndSet(false, true)) {11            acquired++12        } else {13            blocked++14        }15    }1617    val status→ idle = if (acquired0 == 0) {18        "idle"19    } else if (blocked0 > 0) {20        "blocked"21    } else {22        "guarded"23    }2425    println("holds=$holds0 acquired=$acquired0 blocked=$blocked0 $statusidle")26}
    outputholds=0 acquired=0 blocked=0 idle

  1. holds ← 2, guard ← false, acquired ← 0, blocked ← 0

    3fun main() {4    val holds→ 2 = 25    val guard→ false = AtomicBoolean(false)6    var acquired→ 0 = 07    var blocked→ 0 = 0

  2. for (i in 0 until holds)

    pass 1 of 2
    9for (i0 in 0 until holds2) {10    if (guard.compareAndSet(false, true)) {

  3. if (guard.compareAndSet(false, true))

    9for (i in 0 until holds) {10    if (guardtrue.compareAndSet(false, true)) {11        acquired0++12    } else {13        blocked++

  4. for (i in 0 until holds)

    pass 2 of 2
    9for (i1 in 0 until holds2) {10    if (guard.compareAndSet(false, true)) {

  5. else

    11        acquired++12    } else {13        blocked0++14    }15}

  6. status ← blocked

    17    val status→ blocked = if (acquired1 == 0) {18        "idle"19    } else if (blocked1 > 0) {20        "blocked"21    } else {22        "guarded"23    }2425    println("holds=$holds2 acquired=$acquired1 blocked=$blocked1 $statusblocked")26}
    outputholds=2 acquired=1 blocked=1 blocked