Save performing volatile set on LazyValue::set/clear

quarkusio · Jul 13, 2023 · 0728b0e · 0728b0e
1 parent b03e782
commit 0728b0e
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Showing 2 changed files with 34 additions and 8 deletions.
diff --git a/independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/LazyValue.java b/independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/LazyValue.java
@@ -1,5 +1,6 @@
 package io.quarkus.arc.impl;
 
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 import java.util.function.Supplier;
 
 /**
@@ -8,6 +9,9 @@
  */
 public class LazyValue<T> {
 
+    private static final AtomicReferenceFieldUpdater<LazyValue, Object> VALUE_UPDATER = AtomicReferenceFieldUpdater
+            .newUpdater(LazyValue.class, Object.class, "value");
+
     private final Supplier<T> supplier;
 
     private transient volatile T value;
@@ -22,10 +26,14 @@ public T get() {
             return valueCopy;
         }
         synchronized (this) {
-            if (value == null) {
-                value = supplier.get();
+            valueCopy = value;
+            if (valueCopy != null) {
+                return valueCopy;
             }
-            return value;
+            valueCopy = supplier.get();
+            // lazySet == setRelease: it ensure safe publication of the instance
+            VALUE_UPDATER.lazySet(this, valueCopy);
+            return valueCopy;
         }
     }
 
@@ -34,8 +42,13 @@ public T getIfPresent() {
     }
 
     public void clear() {
+        if (value == null) {
+            return;
+        }
         synchronized (this) {
-            value = null;
+            if (value != null) {
+                VALUE_UPDATER.lazySet(this, null);
+            }
         }
     }
 

diff --git a/independent-projects/qute/core/src/main/java/io/quarkus/qute/LazyValue.java b/independent-projects/qute/core/src/main/java/io/quarkus/qute/LazyValue.java
@@ -1,9 +1,13 @@
 package io.quarkus.qute;
 
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 import java.util.function.Supplier;
 
 final class LazyValue<T> {
 
+    private static final AtomicReferenceFieldUpdater<LazyValue, Object> VALUE_UPDATER = AtomicReferenceFieldUpdater
+            .newUpdater(LazyValue.class, Object.class, "value");
+
     private final Supplier<T> supplier;
 
     private transient volatile T value;
@@ -18,10 +22,14 @@ public T get() {
             return valueCopy;
         }
         synchronized (this) {
-            if (value == null) {
-                value = supplier.get();
+            valueCopy = value;
+            if (valueCopy != null) {
+                return valueCopy;
             }
-            return value;
+            valueCopy = supplier.get();
+            // lazySet == setRelease: it ensure safe publication of the instance
+            VALUE_UPDATER.lazySet(this, valueCopy);
+            return valueCopy;
         }
     }
 
@@ -30,8 +38,13 @@ public T getIfPresent() {
     }
 
     public void clear() {
+        if (value == null) {
+            return;
+        }
         synchronized (this) {
-            value = null;
+            if (value != null) {
+                VALUE_UPDATER.lazySet(this, null);
+            }
         }
     }