From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH] net/mlx4_en: ensure rx_desc updating reaches HW before
 prod db updating
Date: Fri, 12 Jan 2018 13:21:59 -0800
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To: Saeed Mahameed <saeedm@mellanox.com>, Jason Gunthorpe <jgg@ziepe.ca>, Jianchao Wang <jianchao.w.wang@oracle.com>
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On Fri, 2018-01-12 at 13:01 -0800, Saeed Mahameed wrote:

> which is better to grasp ?:
> 
> update_doorbell() {
>     dma_wmb();
>     ring->db = prod;
> }

This one is IMO the most secure one (least surprise)

Considering the time it took to discover this bug, I would really play
safe.

But obviously I do not maintain mlx4.