In intrusively linked lists (the one usually used in kernels), you typically already have a pointer to the object, and therefore, to its next/prev pointers. For

In intrusively linked lists (the one usually used in kernels), you typically already have a pointer to the object, and therefore, to its next/prev pointers. For example, removing a task from the scheduler's RUN list and appending to the WAITING list is O(1), because you already have a pointer to the task, because the system's architecture is structured in such a way that you don't have to traverse the RUN list to find the pointer to the task's entry.