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

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Message-ID: <alpine.DEB.2.20.1602171027310.14247@east.gentwo.org>
Date:	Wed, 17 Feb 2016 10:27:59 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Waiman Long <waiman.long@....com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Dave Chinner <david@...morbit.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jan Kara <jack@...e.com>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Tejun Heo <tj@...nel.org>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Chinner <dchinner@...hat.com>,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [RFC PATCH 1/2] lib/percpu-list: Per-cpu list with associated
 per-cpu locks

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.