refactor ReferenceCountedMutex

 - remove synchronisation when removing mutex from map since the mutex
   is only removed once when decrementing the rc to 0
   - this is now guaranteed since the rc cannot increment once reaching
     0 anymore

Author: robinfriedli

README.md

@@ -13,7 +13,7 @@ repositories {
 }
 
 dependencies {
-    implementation "net.robinfriedli:exec:1.1"
+    implementation "net.robinfriedli:exec:1.2"
 }
 ```
 
@@ -22,7 +22,7 @@ dependencies {
 <dependency>
   <groupId>net.robinfriedli</groupId>
   <artifactId>exec</artifactId>
-  <version>1.1</version>
+  <version>1.2</version>
   <type>pom</type>
 </dependency>
 

build.gradle

@@ -6,7 +6,7 @@ plugins {
 }
 
 group = "net.robinfriedli"
-version = "1.1"
+version = "1.2"
 sourceCompatibility = "8"
 targetCompatibility = "8"
 

src/main/kotlin/net/robinfriedli/exec/MutexSync.kt

@@ -28,13 +28,11 @@ class MutexSync<K> {
             }
         }
 
-        // -- thread C is here
         synchronized(mutex) {
             return try {
-                toRun.call() // - thread B is still here
+                toRun.call()
             } finally {
                 mutex.decrementRc()
-                // -- thread A is here (without reference counting it would have removed the mutex)
             }
         }
     }

src/main/kotlin/net/robinfriedli/exec/ReferenceCountedMutex.kt

@@ -10,8 +10,6 @@ class ReferenceCountedMutex<T>(private val key: T, private val containingMap: Mu
 
     private val rc = AtomicInteger(Int.MIN_VALUE)
 
-    private var destroyed = false
-
     fun incrementRc(): Int {
         return rc.updateAndGet { i ->
             when {
@@ -35,13 +33,8 @@ class ReferenceCountedMutex<T>(private val key: T, private val containingMap: Mu
      */
     fun decrementRc(): Boolean {
         val currentRc = rc.decrementAndGet()
-        if (currentRc <= 0) {
-            synchronized(this) {
-                if (!destroyed) {
-                    destroyed = containingMap.remove(key) != null
-                    return destroyed
-                }
-            }
+        if (currentRc == 0) {
+            return containingMap.remove(key) != null
         }
         return false
     }