netdev - Re: [PATCH] net/mlx4_en: ensure rx_desc updating reaches HW before prod db updating

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Date:   Mon, 15 Jan 2018 13:50:34 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Tariq Toukan <tariqt@...lanox.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc:     junxiao.bi@...cle.com, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [PATCH] net/mlx4_en: ensure rx_desc updating reaches HW before
 prod db updating

Hi Tariq

Thanks for your kindly response.

On 01/14/2018 05:47 PM, Tariq Toukan wrote:
> Thanks Jianchao for your patch.
> 
> And Thank you guys for your reviews, much appreciated.
> I was off-work on Friday and Saturday.
> 
> On 14/01/2018 4:40 AM, jianchao.wang wrote:
>> Dear all
>>
>> Thanks for the kindly response and reviewing. That's really appreciated.
>>
>> On 01/13/2018 12:46 AM, Eric Dumazet wrote:
>>>> Does this need to be dma_wmb(), and should it be in
>>>> mlx4_en_update_rx_prod_db ?
>>>>
>>> +1 on dma_wmb()
>>>
>>> On what architecture bug was observed ?
>> This issue was observed on x86-64.
>> And I will send a new patch, in which replace wmb() with dma_wmb(), to customer
>> to confirm.
> 
> +1 on dma_wmb, let us know once customer confirms.
> Please place it within mlx4_en_update_rx_prod_db as suggested.
Yes, I have recommended it to customer.
Once I get the result, I will share it here.
> All other calls to mlx4_en_update_rx_prod_db are in control/slow path so I prefer being on the safe side, and care less about bulking the barrier.
> 
> Thanks,
> Tariq
>