From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v7 1/3] llist: Add a lock-less list variant terminated by
 a sentinel node
Date: Mon, 3 Oct 2022 06:57:37 -1000
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To: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ming Lei <ming.lei-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny-IBi9RG/b67k@public.gmane.org>

On Mon, Oct 03, 2022 at 12:55:24PM -0400, Waiman Long wrote:
> That was my original plan. However, after looking at some existing users of
> lockless list, they have coded in the dependency on the fact that a lockless
> list is empty if it is NULL. I guess I can make this true also for the new
> lockless list with sentinel at the expense of a bit more overhead in the
> entry insertion path and deletion path. I will take a further look at that.

There aren't that many users of llist. Maybe it'd be easier / cleaner to
introduce a macro to test whether a llist is empty and replace the NULL
tests?

Thanks.

-- 
tejun