Remove workaround for bug in Java's ReferenceQueue

Sun's Java 5, 6, 7 implementation had a bug [1] where a Reference can be
enqueued and dequeued twice on the same reference queue due to a race
condition within ReferenceQueue.enqueue(Reference).

This bug was fixed for Java 8 [2] hence remove the workaround.

[1] http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6837858
[2] http://hg.openjdk.java.net/jdk8/jdk8/jdk/rev/858c75eb83b5

Change-Id: I2deeb607e3d237f9f825a207533acdee305c7e73
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/WindowCache.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/WindowCache.java
index a525c851167c26cfa28cd28e327d4a6f854e6fdc..61960068bedfbe135ff9dc3134e31d657aeb7419 100644 (file)
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/WindowCache.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/WindowCache.java
@@ -496,31 +496,16 @@ public class WindowCache {
        private void gc() {
                Ref r;
                while ((r = (Ref) queue.poll()) != null) {
-                       // Sun's Java 5 and 6 implementation have a bug where a Reference
-                       // can be enqueued and dequeued twice on the same reference queue
-                       // due to a race condition within ReferenceQueue.enqueue(Reference).
-                       //
-                       // http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6837858
-                       //
-                       // We CANNOT permit a Reference to come through us twice, as it will
-                       // skew the resource counters we maintain. Our canClear() check here
-                       // provides a way to skip the redundant dequeues, if any.
-                       //
-                       if (r.canClear()) {
-                               clear(r);
-
-                               boolean found = false;
-                               final int s = slot(r.pack, r.position);
-                               final Entry e1 = table.get(s);
-                               for (Entry n = e1; n != null; n = n.next) {
-                                       if (n.ref == r) {
-                                               n.dead = true;
-                                               found = true;
-                                               break;
-                                       }
-                               }
-                               if (found)
+                       clear(r);
+
+                       final int s = slot(r.pack, r.position);
+                       final Entry e1 = table.get(s);
+                       for (Entry n = e1; n != null; n = n.next) {
+                               if (n.ref == r) {
+                                       n.dead = true;
                                        table.compareAndSet(s, e1, clean(e1));
+                                       break;
+                               }
                        }
                }
        }
@@ -581,8 +566,6 @@ public class WindowCache {
 
                long lastAccess;
 
-               private boolean cleared;
-
                protected Ref(final PackFile pack, final long position,
                                final ByteWindow v, final ReferenceQueue<ByteWindow> queue) {
                        super(v, queue);
@@ -590,13 +573,6 @@ public class WindowCache {
                        this.position = position;
                        this.size = v.size();
                }
-
-               final synchronized boolean canClear() {
-                       if (cleared)
-                               return false;
-                       cleared = true;
-                       return true;
-               }
        }
 
        private static final class Lock {