Re: [RFC PATCH 1/2] lib/percpu-list: Per-cpu list with associated per-cpu locks

[Peter Zijlstra]

On Wed, Feb 17, 2016 at 11:16:10AM -0500, Waiman Long wrote:
> >So why not use RCU for the list iteration and avoid potentially large
> >lock hold times?
> >
> 
> I know we can use RCU for singly linked list, but I don't think we can use
> that for doubly linked list as there is no easy way to make atomic changes
> to both prev and next pointers simultaneously unless you are taking about
> 16b cmpxchg which is only supported in some architecture.

See include/linux/rculist.h, the only constraint is that reverse
iteration is not allowed, because of what you say.