check for and handle instances of sun.misc.Cleaner during GC

OpenJDK uses an alternative to Object.finalize for resource cleanup in
the form of sun.misc.Cleaner.  Normally, OpenJDK's
java.lang.ref.Reference.ReferenceHandler thread handles this, calling
Cleaner.clean on any instances it finds in its "pending" queue.
However, Avian handles reference queuing internally, so it never
actually adds anything to that queue, so the VM must call
Cleaner.clean itself.

classpath/sun/misc/Cleaner.java

@@ -0,0 +1,13 @@
+/* Copyright (c) 2011, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package sun.misc;
+
+public class Cleaner { }

src/machine.cpp

@@ -379,26 +379,33 @@ referenceTargetUnreachable(Thread* t, Heap::Visitor* v, object* p)
   v->visit(p);
   jreferenceTarget(t, *p) = 0;
 
-  if (jreferenceQueue(t, *p)
+  if (objectClass(t, *p) == type(t, Machine::CleanerType)) {
-      and t->m->heap->status(jreferenceQueue(t, *p)) != Heap::Unreachable)
+    object reference = *p;
-  {
+    *p = jreferenceVmNext(t, reference);
-    // queue is reachable - add the reference
+    jreferenceVmNext(t, reference) = t->m->cleanerQueue;
+    t->m->cleanerQueue = reference;
+  } else {
+    if (jreferenceQueue(t, *p)
+        and t->m->heap->status(jreferenceQueue(t, *p)) != Heap::Unreachable)
+    {
+      // queue is reachable - add the reference
 
-    v->visit(&jreferenceQueue(t, *p));
+      v->visit(&jreferenceQueue(t, *p));
 
-    object q = jreferenceQueue(t, *p);
+      object q = jreferenceQueue(t, *p);
 
-    if (referenceQueueFront(t, q)) {
+      if (referenceQueueFront(t, q)) {
-      set(t, *p, JreferenceJNext, referenceQueueFront(t, q));
+        set(t, *p, JreferenceJNext, referenceQueueFront(t, q));
-    } else {
+      } else {
-      set(t, *p, JreferenceJNext, *p);
+        set(t, *p, JreferenceJNext, *p);
+      }
+      set(t, q, ReferenceQueueFront, *p);
+
+      jreferenceQueue(t, *p) = 0;
     }
-    set(t, q, ReferenceQueueFront, *p);
 
-    jreferenceQueue(t, *p) = 0;
+    *p = jreferenceVmNext(t, *p);
   }
-
-  *p = jreferenceVmNext(t, *p);
 }
 
 void
@@ -446,6 +453,7 @@ postVisit(Thread* t, Heap::Visitor* v)
   bool major = m->heap->collectionType() == Heap::MajorCollection;
 
   assert(t, m->finalizeQueue == 0);
+  assert(t, m->cleanerQueue == 0);
 
   object firstNewTenuredFinalizer = 0;
   object lastNewTenuredFinalizer = 0;
@@ -611,13 +619,13 @@ invoke(Thread* t, uintptr_t* arguments)
 }
 
 void
-finalizeObject(Thread* t, object o)
+finalizeObject(Thread* t, object o, const char* name)
 {
   for (object c = objectClass(t, o); c; c = classSuper(t, c)) {
     for (unsigned i = 0; i < arrayLength(t, classMethodTable(t, c)); ++i) {
       object m = arrayBody(t, classMethodTable(t, c), i);
 
-      if (vm::strcmp(reinterpret_cast<const int8_t*>("finalize"),
+      if (vm::strcmp(reinterpret_cast<const int8_t*>(name),
                      &byteArrayBody(t, methodName(t, m), 0)) == 0
           and vm::strcmp(reinterpret_cast<const int8_t*>("()V"),
                          &byteArrayBody(t, methodSpec(t, m), 0)) == 0)
@@ -2254,19 +2262,36 @@ doCollect(Thread* t, Heap::CollectionType type)
   if (not stress) atomicAnd(&(t->flags), ~Thread::StressFlag);
 #endif
 
-  object f = t->m->finalizeQueue;
+  object finalizeQueue = t->m->finalizeQueue;
+  PROTECT(t, finalizeQueue);
   t->m->finalizeQueue = 0;
-  for (; f; f = finalizerNext(t, f)) {
+  for (; finalizeQueue; finalizeQueue = finalizerNext(t, finalizeQueue)) {
     void (*function)(Thread*, object);
-    memcpy(&function, &finalizerFinalize(t, f), BytesPerWord);
+    memcpy(&function, &finalizerFinalize(t, finalizeQueue), BytesPerWord);
     if (function) {
-      function(t, finalizerTarget(t, f));
+      function(t, finalizerTarget(t, finalizeQueue));
     } else {
-      setRoot(t, Machine::ObjectsToFinalize, makePair
+      setRoot(t, Machine::ObjectsToFinalize, makeFinalizeNode
-              (t, finalizerTarget(t, f), root(t, Machine::ObjectsToFinalize)));
+              (t, finalizerTarget(t, finalizeQueue),
+               const_cast<char*>("finalize"),
+               root(t, Machine::ObjectsToFinalize)));
     }
   }
 
+  object cleanerQueue = t->m->cleanerQueue;
+  PROTECT(t, cleanerQueue);
+  t->m->cleanerQueue = 0;
+  while (cleanerQueue) {
+    setRoot(t, Machine::ObjectsToFinalize, makeFinalizeNode
+            (t, cleanerQueue,
+             const_cast<char*>("clean"),
+             root(t, Machine::ObjectsToFinalize)));
+
+    object tmp = cleanerQueue;
+    cleanerQueue = jreferenceVmNext(t, cleanerQueue);
+    jreferenceVmNext(t, tmp) = 0;
+  }
+
   if (root(t, Machine::ObjectsToFinalize) and m->finalizeThread == 0) {
     m->finalizeThread = m->processor->makeThread
       (m, root(t, Machine::FinalizerThread), m->rootThread);
@@ -2330,6 +2355,7 @@ Machine::Machine(System* system, Heap* heap, Finder* bootFinder,
   finalizers(0),
   tenuredFinalizers(0),
   finalizeQueue(0),
+  cleanerQueue(0),
   weakReferences(0),
   tenuredWeakReferences(0),
   unsafe(false),
@@ -4099,8 +4125,10 @@ runFinalizeThread(Thread* t)
       }
     }
 
-    for (; list; list = pairSecond(t, list)) {
+    for (; list; list = finalizeNodeNext(t, list)) {
-      finalizeObject(t, pairFirst(t, list));
+      finalizeObject
+        (t, finalizeNodeTarget(t, list),
+         static_cast<const char*>(finalizeNodeMethodName(t, list)));
     }
   }
 }

src/machine.h

@@ -1311,6 +1311,7 @@ class Machine {
   object finalizers;
   object tenuredFinalizers;
   object finalizeQueue;
+  object cleanerQueue;
   object weakReferences;
   object tenuredWeakReferences;
   bool unsafe;

src/types.def

@@ -106,6 +106,11 @@
   (void* finalize)
   (nogc object next))
 
+(type finalizeNode
+  (object target)
+  (void* methodName)
+  (object next))
+
 (type hashMap
   (uint32_t size)
   (object array))
@@ -294,6 +299,8 @@
 
 (type phantomReference java/lang/ref/PhantomReference)
 
+(type cleaner sun/misc/Cleaner)
+
 (type byteArray [B
   (extends jobject)
   (array int8_t body))