From d178a7404f8ed3896dbf7b72826aa8ec2438ee61 Mon Sep 17 00:00:00 2001
From: "David M. Lloyd" <david.lloyd@redhat.com>
Date: Fri, 25 Aug 2023 09:47:15 -0500
Subject: [PATCH] Allow reaper threads to be started at run time

---
 ref/pom.xml                                   |  4 ++
 .../smallrye/common/ref/PhantomReference.java |  2 +-
 .../io/smallrye/common/ref/References.java    | 46 ++++++++++++++-----
 .../io/smallrye/common/ref/SoftReference.java |  2 +-
 .../io/smallrye/common/ref/WeakReference.java |  2 +-
 5 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/ref/pom.xml b/ref/pom.xml
index 44ef7736..a7ddac7a 100644
--- a/ref/pom.xml
+++ b/ref/pom.xml
@@ -17,6 +17,10 @@
             <groupId>${project.groupId}</groupId>
             <artifactId>smallrye-common-constraint</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.graalvm.sdk</groupId>
+            <artifactId>graal-sdk</artifactId>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/ref/src/main/java/io/smallrye/common/ref/PhantomReference.java b/ref/src/main/java/io/smallrye/common/ref/PhantomReference.java
index 67722743..d7a13321 100644
--- a/ref/src/main/java/io/smallrye/common/ref/PhantomReference.java
+++ b/ref/src/main/java/io/smallrye/common/ref/PhantomReference.java
@@ -36,7 +36,7 @@ public PhantomReference(final T referent, final A attachment, final ReferenceQue
      * @param reaper the reaper to use
      */
     public PhantomReference(final T referent, final A attachment, final Reaper<T, A> reaper) {
-        super(referent, References.ReaperThread.REAPER_QUEUE);
+        super(referent, References.ReaperThread.getReaperQueue());
         this.reaper = reaper;
         this.attachment = attachment;
     }
diff --git a/ref/src/main/java/io/smallrye/common/ref/References.java b/ref/src/main/java/io/smallrye/common/ref/References.java
index 1ac18f1b..52a626e0 100644
--- a/ref/src/main/java/io/smallrye/common/ref/References.java
+++ b/ref/src/main/java/io/smallrye/common/ref/References.java
@@ -6,6 +6,8 @@
 import java.security.PrivilegedAction;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import org.graalvm.nativeimage.ImageInfo;
+
 import io.smallrye.common.constraint.Assert;
 
 /**
@@ -17,27 +19,47 @@ private References() {
 
     private static final Reference<?, ?> NULL = new StrongReference<>(null);
 
-    static final class ReaperThread extends Thread {
+    static final class BuildTimeHolder {
         static final ReferenceQueue<Object> REAPER_QUEUE = new ReferenceQueue<Object>();
+    }
+
+    static final class ReaperThread extends Thread {
+        static ReferenceQueue<Object> getReaperQueue() {
+            return BuildTimeHolder.REAPER_QUEUE;
+        }
 
         static {
-            final AtomicInteger cnt = new AtomicInteger(1);
-            final PrivilegedAction<Void> action = () -> {
-                final ReaperThread thr = new ReaperThread();
-                thr.setName("Reference Reaper #" + cnt.getAndIncrement());
-                thr.setDaemon(true);
-                thr.start();
-                return null;
-            };
-            for (int i = 0; i < 3; i++) {
-                doPrivileged(action);
+            if (isBuildTime()) {
+                // do nothing (class should be reinitialized)
+            } else {
+                final AtomicInteger cnt = new AtomicInteger(1);
+                final PrivilegedAction<Void> action = () -> startThreadAction(cnt.getAndIncrement());
+                for (int i = 0; i < 3; i++) {
+                    doPrivileged(action);
+                }
+            }
+        }
+
+        private static boolean isBuildTime() {
+            try {
+                return ImageInfo.inImageBuildtimeCode();
+            } catch (Throwable ignored) {
+                return false;
             }
         }
 
+        private static Void startThreadAction(int id) {
+            final ReaperThread thr = new ReaperThread();
+            thr.setName("Reference Reaper #" + id);
+            thr.setDaemon(true);
+            thr.start();
+            return null;
+        }
+
         public void run() {
             for (;;)
                 try {
-                    final java.lang.ref.Reference<?> ref = REAPER_QUEUE.remove();
+                    final java.lang.ref.Reference<?> ref = ReaperThread.getReaperQueue().remove();
                     if (ref instanceof CleanerReference) {
                         ((CleanerReference<?, ?>) ref).clean();
                     }
diff --git a/ref/src/main/java/io/smallrye/common/ref/SoftReference.java b/ref/src/main/java/io/smallrye/common/ref/SoftReference.java
index 93b82209..211a1d05 100644
--- a/ref/src/main/java/io/smallrye/common/ref/SoftReference.java
+++ b/ref/src/main/java/io/smallrye/common/ref/SoftReference.java
@@ -55,7 +55,7 @@ public SoftReference(final T referent, final A attachment, final ReferenceQueue<
      * @param reaper the reaper to use
      */
     public SoftReference(final T referent, final A attachment, final Reaper<T, A> reaper) {
-        super(referent, References.ReaperThread.REAPER_QUEUE);
+        super(referent, References.ReaperThread.getReaperQueue());
         this.reaper = reaper;
         this.attachment = attachment;
     }
diff --git a/ref/src/main/java/io/smallrye/common/ref/WeakReference.java b/ref/src/main/java/io/smallrye/common/ref/WeakReference.java
index 688970a2..fc7c33f6 100644
--- a/ref/src/main/java/io/smallrye/common/ref/WeakReference.java
+++ b/ref/src/main/java/io/smallrye/common/ref/WeakReference.java
@@ -55,7 +55,7 @@ public WeakReference(final T referent, final A attachment, final ReferenceQueue<
      * @param reaper the reaper to use
      */
     public WeakReference(final T referent, final A attachment, final Reaper<T, A> reaper) {
-        super(referent, References.ReaperThread.REAPER_QUEUE);
+        super(referent, References.ReaperThread.getReaperQueue());
         this.attachment = attachment;
         this.reaper = reaper;
     }