Re: [PATCH v7 1/3] llist: Add a lock-less list variant terminated by a sentinel node

From: Tejun Heo <tj@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
	cgroups@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, "Ming Lei" <ming.lei@redhat.com>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Michal Koutný" <mkoutny@suse.com>
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	[thread overview]
Message-ID: <YzsUgY4CC0SH8Sl2@slm.duckdns.org> (raw)
In-Reply-To: <006ebc52-ab37-442a-9ba3-e7b8dff53fab@redhat.com>

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