From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next 01/17] net: sched: refactor
 mini_qdisc_pair_swap() to use workqueue
Date: Mon, 12 Nov 2018 09:28:09 -0800 (PST)
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From: Vlad Buslov <vladbu@mellanox.com>
Date: Mon, 12 Nov 2018 09:55:30 +0200

> +void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
> +			  struct tcf_proto *tp_head)
> +{
> +	xchg(&miniqp->tp_head, tp_head);

If you are not checking the return value of xchg(), then this is
simply a store with optionally a memory barrier of some sort
either before or after.