From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <olivier.matz@6wind.com>
Received: from mail.droids-corp.org (zoll.droids-corp.org [94.23.50.67])
 by dpdk.org (Postfix) with ESMTP id 2354B5961
 for <dev@dpdk.org>; Fri, 11 Apr 2014 11:40:39 +0200 (CEST)
Received: from was59-1-82-226-113-214.fbx.proxad.net ([82.226.113.214]
 helo=platinum.localnet)
 by mail.droids-corp.org with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256)
 (Exim 4.80) (envelope-from <olivier.matz@6wind.com>)
 id 1WYXzl-0001Wh-Vx for dev@dpdk.org; Fri, 11 Apr 2014 11:43:44 +0200
From: Olivier MATZ <olivier.matz@6wind.com>
To: dev@dpdk.org
Date: Fri, 11 Apr 2014 11:41:46 +0200
Message-ID: <2469493.IGjSGz2PDr@platinum>
Organization: 6WIND
User-Agent: KMail/4.11.3 (Linux/3.12.6; KDE/4.11.3; x86_64; ; )
In-Reply-To: <7F861DC0615E0C47A872E6F3C5FCDDBD0109D69F@BPXM14GP.gisp.nec.co.jp>
References: <7F861DC0615E0C47A872E6F3C5FCDDBD0109D69F@BPXM14GP.gisp.nec.co.jp>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Subject: Re: [dpdk-dev] [memnic PATCH] linux: fix race condition
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
X-List-Received-Date: Fri, 11 Apr 2014 09:40:39 -0000

On Thursday, April 03, 2014 07:35:50 AM Hiroshi Shimamoto wrote:
> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> 
> Same as PMD, there is a race condition between host and guest
> in the guest MEMNIC kernel driver.
> 
> Guest PMD                 Host
> Thread-A     Thread-B     vSwitch
> 
>    |idx=0       |idx=0       |p[0] st!=2
>    |cmpxchg     |            |
>    |p[0] st->1  |            |
>    |idx=1       |            |
>    |fill data   |            |
>    |p[0] st->2  |            |p[0] st==2
>    |
>    |            |            |receive data
>    |            |            |p[0] st->0
>    |            |
>    |            |cmpxchg     |
>    |            |success     |p[1] st!=2
>    |            |p[0] st->1  |
> 
>                   This is BAD
> 
> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> ---
>  linux/memnic_net.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Reviewed-by: Olivier Matz <olivier.matz@6wind.com>