--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/lang/invoke/VolatileCallSite.java	Wed Mar 23 23:02:31 2011 -0700
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.lang.invoke;
+
+/**
+ * A {@code VolatileCallSite} is a {@link CallSite} whose target acts like a volatile variable.
+ * An {@code invokedynamic} instruction linked to a {@code VolatileCallSite} sees updates
+ * to its call site target immediately, even if the update occurs in another thread.
+ * There may be a performance penalty for such tight coupling between threads.
+ * <p>
+ * Unlike {@code MutableCallSite}, there is no
+ * {@linkplain MutableCallSite#syncAll syncAll operation} on volatile
+ * call sites, since every write to a volatile variable is implicitly
+ * synchronized with reader threads.
+ * <p>
+ * In other respects, a {@code VolatileCallSite} is interchangeable
+ * with {@code MutableCallSite}.
+ * @see MutableCallSite
+ * @author John Rose, JSR 292 EG
+ */
+public class VolatileCallSite extends CallSite {
+    /**
+     * Creates a call site with a volatile binding to its target.
+     * The initial target is set to a method handle
+     * of the given type which will throw an {@code IllegalStateException} if called.
+     * @param type the method type that this call site will have
+     * @throws NullPointerException if the proposed type is null
+     */
+    public VolatileCallSite(MethodType type) {
+        super(type);
+    }
+
+    /**
+     * Creates a call site with a volatile binding to its target.
+     * The target is set to the given value.
+     * @param target the method handle that will be the initial target of the call site
+     * @throws NullPointerException if the proposed target is null
+     */
+    public VolatileCallSite(MethodHandle target) {
+        super(target);
+    }
+
+    /**
+     * Returns the target method of the call site, which behaves
+     * like a {@code volatile} field of the {@code VolatileCallSite}.
+     * <p>
+     * The interactions of {@code getTarget} with memory are the same
+     * as of a read from a {@code volatile} field.
+     * <p>
+     * In particular, the current thread is required to issue a fresh
+     * read of the target from memory, and must not fail to see
+     * a recent update to the target by another thread.
+     *
+     * @return the linkage state of this call site, a method handle which can change over time
+     * @see #setTarget
+     */
+    @Override public final MethodHandle getTarget() {
+        return getTargetVolatile();
+    }
+
+    /**
+     * Updates the target method of this call site, as a volatile variable.
+     * The type of the new target must agree with the type of the old target.
+     * <p>
+     * The interactions with memory are the same as of a write to a volatile field.
+     * In particular, any threads is guaranteed to see the updated target
+     * the next time it calls {@code getTarget}.
+     * @param newTarget the new target
+     * @throws NullPointerException if the proposed new target is null
+     * @throws WrongMethodTypeException if the proposed new target
+     *         has a method type that differs from the previous target
+     * @see #getTarget
+     */
+    @Override public void setTarget(MethodHandle newTarget) {
+        checkTargetChange(getTargetVolatile(), newTarget);
+        setTargetVolatile(newTarget);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public final MethodHandle dynamicInvoker() {
+        return makeDynamicInvoker();
+    }
+}