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Date: Wed, 17 Feb 2016 10:27:59 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
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To: Waiman Long <waiman.long@hpe.com>
cc: Peter Zijlstra <peterz@infradead.org>, Dave Chinner <david@fromorbit.com>,
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        Ingo Molnar <mingo@redhat.com>, Andi Kleen <andi@firstfloor.org>,
        Dave Chinner <dchinner@redhat.com>,
        Scott J Norton <scott.norton@hp.com>,
        Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [RFC PATCH 1/2] lib/percpu-list: Per-cpu list with associated
 per-cpu locks
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On Wed, 17 Feb 2016, Waiman Long wrote:

> 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.

But its supported in the most important architecutes. You can fall back to
spinlocks on the ones that do not support it.