netdev - Re: [PATCH net-next 01/17] net: sched: refactor mini_qdisc_pair

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Date:   Tue, 13 Nov 2018 13:13:19 +0000
From:   Vlad Buslov <vladbu@...lanox.com>
To:     David Miller <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>
Subject: Re: [PATCH net-next 01/17] net: sched: refactor
 mini_qdisc_pair_swap() to use workqueue


On Mon 12 Nov 2018 at 17:28, David Miller <davem@...emloft.net> wrote:
> From: Vlad Buslov <vladbu@...lanox.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.

That was my intention. What would be a better way to atomically
reset a pointer? Should I just change this line to explicit
assignment+barrier?