diff --git a/core/src/main/java/hudson/CopyOnWrite.java b/core/src/main/java/hudson/CopyOnWrite.java
new file mode 100644
index 0000000000..25443133bb
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+++ b/core/src/main/java/hudson/CopyOnWrite.java
@@ -0,0 +1,31 @@
+package hudson;
+
+import java.lang.annotation.Documented;
+import static java.lang.annotation.ElementType.FIELD;
+import java.lang.annotation.Retention;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+import java.lang.annotation.Target;
+
+/**
+ * Represents fields that are protected for concurrency by the copy-on-write semantics.
+ *
+ * <p>
+ * Fields marked by this annotation always holds on to an immutable collection.
+ * A change to the collection must be done by first creating a new collection
+ * object, making changes, then replacing the reference atomically.
+ *
+ * <p>
+ * This allows code to access the field without synchronization, and
+ * greatly reduces the risk of dead-lock bugs.
+ *
+ * <p>
+ * The field marked with this annotation usually needs to be marked as
+ * <tt>volatile</tt>.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+@Retention(SOURCE)
+@Documented
+@Target(FIELD)
+public @interface CopyOnWrite {
+}