The first state shows a linked list containing elements , , and . All three elements are colored red to indicate that an RCU reader might reference any of them at any time. Using to remove element from this list transitions to the second state. Note that the link from element B to C is left intact in order to allow readers currently referencing element to traverse the remainder of the list. Readers accessing the link from element will either obtain a reference to element or element , but either way, each reader will see a valid and correctly formatted linked list. Element is now colored yellow to indicate that while pre-existing readers might still have a reference to element , new readers have no way to obtain a reference. A wait-for-readers operation transitions to the third state. Note that this wait-for-readers operation need only wait for pre-existing readers, but not new readers. Element is now colored green to indicate that readers can no longer be referencing it. Therefore, it is now safe for the updater to free element , thus transitioning to the fourth and final state.