Small cleanup in FinalizationService

* Clarify what happens when removing the last FinalizerReference.

Author: eregon

src/main/java/org/truffleruby/core/FinalizationService.java

@@ -55,6 +55,8 @@ public DynamicObject getRoot() {
 
     public static class FinalizerReference extends PhantomReference<Object> {
 
+        private static FinalizerReference first = null;
+
         /**
          * All accesses to this Deque must be synchronized by taking the
          * {@link FinalizationService} monitor, to avoid concurrent access.
@@ -63,8 +65,6 @@ public static class FinalizerReference extends PhantomReference<Object> {
         private FinalizerReference next = null;
         private FinalizerReference prev = null;
 
-        private static FinalizerReference first = null;
-
         private FinalizerReference(Object object, ReferenceQueue<? super Object> queue) {
             super(object, queue);
         }
@@ -98,19 +98,13 @@ private void collectRoots(Collection<DynamicObject> roots) {
     }
 
     private final RubyContext context;
-
     private final ReferenceQueue<Object> finalizerQueue = new ReferenceQueue<>();
-
     private DynamicObject finalizerThread;
 
     public FinalizationService(RubyContext context) {
         this.context = context;
     }
 
-    public FinalizerReference addFinalizer(Object object, FinalizerReference ref, Class<?> owner, Runnable action) {
-        return addFinalizer(object, ref, owner, action, null);
-    }
-
     public synchronized FinalizerReference addFinalizer(Object object, FinalizerReference finalizerReference, Class<?> owner, Runnable action, DynamicObject root) {
 
         if (finalizerReference == null) {
@@ -163,17 +157,18 @@ private void createFinalizationThread() {
 
         threadManager.initialize(finalizerThread, null, "finalizer", () -> {
             while (true) {
-                final FinalizerReference finalizerReference = (FinalizerReference) threadManager.runUntilResult(null,
-                        finalizerQueue::remove);
+                final FinalizerReference finalizerReference =
+                        (FinalizerReference) threadManager.runUntilResult(null, finalizerQueue::remove);
 
                 runFinalizer(finalizerReference);
             }
         });
     }
 
     private void runFinalizer(FinalizerReference finalizerReference) {
+        FinalizationService.remove(finalizerReference);
+
         try {
-            FinalizationService.remove(finalizerReference);
             while (!context.isFinalizing()) {
                 final Finalizer finalizer;
                 synchronized (this) {
@@ -213,7 +208,7 @@ public synchronized FinalizerReference removeFinalizers(Object object, Finalizer
         }
     }
 
-    static synchronized void remove(FinalizerReference ref) {
+    private static synchronized void remove(FinalizerReference ref) {
         if (ref.next == ref) {
             // Already removed.
             return;
@@ -223,7 +218,8 @@ static synchronized void remove(FinalizerReference ref) {
             if (ref.next != null) {
                 FinalizerReference.first = ref.next;
             } else {
-                FinalizerReference.first = ref.prev;
+                // The list becomes empty
+                FinalizerReference.first = null;
             }
         }
 
@@ -239,7 +235,7 @@ static synchronized void remove(FinalizerReference ref) {
         ref.prev = ref;
     }
 
-    static synchronized void add(FinalizerReference newRef) {
+    private static synchronized void add(FinalizerReference newRef) {
         if (FinalizerReference.first != null) {
             newRef.next = FinalizerReference.first;
             FinalizerReference.first.prev = newRef;

src/main/java/org/truffleruby/extra/ffi/Pointer.java

@@ -248,7 +248,7 @@ public synchronized void enableAutorelease(FinalizationService finalizationServi
 
         // We must be careful here that the finalizer does not capture the Pointer itself that we'd
         // like to finalize.
-        finalizerRef = finalizationService.addFinalizer(this, finalizerRef, Pointer.class, new FreeAddressFinalizer(address));
+        finalizerRef = finalizationService.addFinalizer(this, finalizerRef, Pointer.class, new FreeAddressFinalizer(address), null);
 
         autorelease = true;
     }