From 3412d4c0dd5250f14cc6fe594355bdf2ff976417 Mon Sep 17 00:00:00 2001
From: Per Minborg <pminborg@openjdk.org>
Date: Sat, 25 Jul 2026 07:54:18 +0000
Subject: [PATCH] 8387722: The race during initialization or lazy constants in
 and Map/Set

Reviewed-by: jvernee
---
 src/java.base/share/classes/java/util/LazyCollections.java | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/java.base/share/classes/java/util/LazyCollections.java b/src/java.base/share/classes/java/util/LazyCollections.java
index e15721db2ce..f74fbad358b 100644
--- a/src/java.base/share/classes/java/util/LazyCollections.java
+++ b/src/java.base/share/classes/java/util/LazyCollections.java
@@ -675,6 +675,12 @@ final class LazyCollections {
         final long offset = offsetFor(index);
         final Object mutex = mutexes.acquireMutex(offset);
         if (mutex == null) {
+            // There might be a race where the value is already computed and
+            // the mutex is cleared, so we need to re-check the value again
+            final T t = (T) UNSAFE.getReferenceAcquire(array, offset);
+            if (t != null) {
+                return t;
+            }
             throwIfPreviousException(index, throwables, input);
             // There must be an exception
             throw cannotReachHere(functionHolder, input);