netdev - Re: [PATCH net] amd-xgbe: Use wmb before updating current descriptor count

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <562A37B8.2090108@amd.com>
Date:	Fri, 23 Oct 2015 08:35:52 -0500
From:	Tom Lendacky <thomas.lendacky@....com>
To:	David Miller <davem@...emloft.net>
CC:	<netdev@...r.kernel.org>, <christoffer.dall@...aro.org>
Subject: Re: [PATCH net] amd-xgbe: Use wmb before updating current descriptor
 count

On 10/23/2015 04:59 AM, David Miller wrote:
> From: Tom Lendacky <thomas.lendacky@....com>
> Date: Wed, 21 Oct 2015 15:37:05 -0500
>
>> The code currently uses the lightweight dma_wmb barrier before updating
>> the current descriptor count. Under heavy load, the Tx cleanup routine
>> was seeing the updated current descriptor count before the updated
>> descriptor information. As a result, the Tx descriptor was being cleaned
>> up before it was used because it was not "owned" by the hardware yet,
>> resulting in a Tx queue hang.
>>
>> Using the wmb barrier insures that the descriptor is updated before the
>> descriptor counter preventing the Tx queue hang. For extra insurance,
>> the Tx cleanup routine is changed to grab the current decriptor count on
>> entry and uses that initial value in the processing loop rather than
>> trying to chase the current value.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> Tested-by: Christoffer Dall <christoffer.dall@...aro.org>
>
> Applied, thanks.

Hi David,

Can you queue this up for stable?  It is applicable to 4.1 and 4.2.

Thanks,
Tom

>
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html