From 0728b0eb0f2dbd037b4b371048803b205640ae38 Mon Sep 17 00:00:00 2001
From: franz1981 <nigro.fra@gmail.com>
Date: Mon, 3 Jul 2023 14:49:30 +0200
Subject: [PATCH] Save performing volatile set on LazyValue::set/clear

---
 .../java/io/quarkus/arc/impl/LazyValue.java   | 21 +++++++++++++++----
 .../main/java/io/quarkus/qute/LazyValue.java  | 21 +++++++++++++++----
 2 files changed, 34 insertions(+), 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
index 5c383b25516eb..2618a82938d65 100644
--- 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
index 53f3195feedba..713f83998ee56 100644
--- 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);
+            }
         }
     }