From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas.monjalon@6wind.com>
Subject: Re: [PATCH RFC v3 0/3] Thread safe
	rte_vhost_enqueue_burst().
Date: Fri, 18 Mar 2016 10:34:56 +0100
Message-ID: <3519170.fnd0yd7nVF@xps13>
References: <1456314438-4021-1-git-send-email-i.maximets@samsung.com>
 <9470086.ZYvecjaNVJ@xps13> <20160318091614.GT979@yliu-dev.sh.intel.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7Bit
Cc: dev@dpdk.org, Ilya Maximets <i.maximets@samsung.com>,
 Huawei Xie <huawei.xie@intel.com>, bruce.richardson@intel.com,
 Dyasly Sergey <s.dyasly@samsung.com>,
 Jerin Jacob <jerin.jacob@caviumnetworks.com>,
 Jianbo Liu <jianbo.liu@linaro.org>, Tetsuya Mukawa <mukawa@igel.co.jp>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Return-path: <dev-bounces@dpdk.org>
Received: from mail-wm0-f50.google.com (mail-wm0-f50.google.com [74.125.82.50])
 by dpdk.org (Postfix) with ESMTP id B284C2C67
 for <dev@dpdk.org>; Fri, 18 Mar 2016 10:36:27 +0100 (CET)
Received: by mail-wm0-f50.google.com with SMTP id p65so60205200wmp.1
 for <dev@dpdk.org>; Fri, 18 Mar 2016 02:36:27 -0700 (PDT)
In-Reply-To: <20160318091614.GT979@yliu-dev.sh.intel.com>
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>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

2016-03-18 17:16, Yuanhan Liu:
> On Fri, Mar 18, 2016 at 09:09:04AM +0100, Thomas Monjalon wrote:
> > 2016-03-18 16:00, Yuanhan Liu:
> > > On Thu, Mar 17, 2016 at 04:29:32PM +0100, Thomas Monjalon wrote:
> > > > 2016-02-24 14:47, Ilya Maximets:
> > > > > Implementation of rte_vhost_enqueue_burst() based on lockless ring-buffer
> > > > > algorithm and contains almost all to be thread-safe, but it's not.
> > > > > 
> > > > > This set adds required changes.
> > > > > 
> > > > > First patch in set is a standalone patch that fixes many times discussed
> > > > > issue with barriers on different architectures.
> > > > > 
> > > > > Second and third adds fixes to make rte_vhost_enqueue_burst thread safe.
> > > > 
> > > > My understanding is that we do not want to pollute Rx/Tx with locks.
> > > > 
> > > > Huawei, Yuanhan, Bruce, do you confirm?
> > > 
> > > Huawei would like to do that, and I'm behind that. Let's do it.
> > 
> > I'm not sure to understand. What do you want to do exactly?
> 
> I was thinking we are on the same page :(

Yes we are on the same page.
But it's better to make things explicit.

There should be no lock in Rx/Tx drivers (including vhost).
The locking must be done by the caller (application level).
That's why this series "Thread safe rte_vhost_enqueue_burst" is rejected.

> "do not want to pollute Rx/Tx with locks" == "remove lockless Rx/Tx, the
> proposal from Huawei", right?
> 
> In another way, I'm behind the following patch from Huawei:
> 
>     http://dpdk.org/dev/patchwork/patch/9740/

The patch "vhost: remove lockless enqueue to the virtio ring" must me
reworked in 2 patches:
1/ announce API change
2/ remove locks

Please avoid talking about removing "lockless" when actually removing locks.

Thanks