From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <thomas@monjalon.net> Received: from out3-smtp.messagingengine.com (out3-smtp.messagingengine.com [66.111.4.27]) by dpdk.org (Postfix) with ESMTP id 5434B7D52 for <dev@dpdk.org>; Fri, 8 Dec 2017 12:35:20 +0100 (CET) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id CACDB20CF3; Fri, 8 Dec 2017 06:35:19 -0500 (EST) Received: from frontend2 ([10.202.2.161]) by compute1.internal (MEProxy); Fri, 08 Dec 2017 06:35:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-sender :x-me-sender:x-sasl-enc; s=mesmtp; bh=fRZIU9yIcSUIIWQvaONoUQLLX2 vt3zT4C8nO6tsfP6s=; b=RuZqEejxuYrGEcINOUO63UQT4SW/1O8kFsa8rpTljL KuyMa/3/33RFLNCiFX0H0//yJG29bhxikxLeJKzBVzm6Dfa+qWz6Onop8ajjNjIF OzdisPctNbek9Sv8/d0lsQt2V9NTjvQVAbhjSy7Thp54pOa8CmzrdKeK+B9k9IXd 8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; bh=fRZIU9 yIcSUIIWQvaONoUQLLX2vt3zT4C8nO6tsfP6s=; b=RSY9u4irC+XqUPrJbXAOSV uzQ/7rQLwGpa69GKGt9C47SLHsC1hNaQf/Wk/Zr4WvmGLgl0i3KIAerZ0SbrtRE5 pR3uXR+5Dys6y4EfuxNGhwn6TUqaKoI2tMVag9XJGjhFp/PkCHDHYM+5Ko8AG1tZ SqhMxM8VihmuI1TQyS5ULhJB+J82dAaXccrTtPh8fc9xmWjJYTReR2x6nW8ZxtwA 3wc2O0Y3Rw1kQPmI5K4LQXsA26wzl16GnicEoN5ZKmA8Dd/9T2KIAhy5e4TUl8YA 3HfUIOY0bAiLD5PqncLbON2tuhWNNrhiH8T7Lr0/2pvT5T0KdR3kbQJ+tytQaHZg == X-ME-Sender: <xms:93gqWqxsAwJoCEWjQ49F4k5XThl8DWAb_m_zyKoKzJDFA6WGy8wyOA> Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id 7882024136; Fri, 8 Dec 2017 06:35:19 -0500 (EST) From: Thomas Monjalon <thomas@monjalon.net> To: Bruce Richardson <bruce.richardson@intel.com> Cc: Matan Azrad <matan@mellanox.com>, Neil Horman <nhorman@tuxdriver.com>, "Ananyev, Konstantin" <konstantin.ananyev@intel.com>, =?ISO-8859-1?Q?Ga=EBtan?= Rivet <gaetan.rivet@6wind.com>, "Wu, Jingjing" <jingjing.wu@intel.com>, dev@dpdk.org Date: Fri, 08 Dec 2017 12:35:18 +0100 Message-ID: <5212147.QN8ImyqEg2@xps> In-Reply-To: <20171205100542.GA7492@bricha3-MOBL3.ger.corp.intel.com> References: <20171130123611.GA20914@hmswarspite.think-freely.org> <HE1PR0502MB3659563360991F8F0C650D0DD23D0@HE1PR0502MB3659.eurprd05.prod.outlook.com> <20171205100542.GA7492@bricha3-MOBL3.ger.corp.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH 2/5] ethdev: add port ownership X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions <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, 08 Dec 2017 11:35:20 -0000 05/12/2017 11:05, Bruce Richardson: > > I think you suggest to make all the ethdev configuration race safe, it > > is behind to this thread. Current ethdev implementation leave the > > race management to applications, so port ownership as any other port > > configurations should be designed in the same method. > > One key difference, though, being that port ownership itself could be > used to manage the thread-safety of the ethdev configuration. It's also > a little different from other APIs in that I find it hard to come up > with a scenario where it would be very useful to an application without > also having some form of locking present in it. For other config/control > APIs we can have the control plane APIs work without locks e.g. by > having a single designated thread/process manage all configuration > updates. However, as Neil points out, in such a scenario, the ownership > concept doesn't provide any additional benefit so can be skipped > completely. I'd view it a bit like the reference counting of mbufs - > we can provide a lockless/non-atomic version, but for just about every > real use-case, you want the atomic version. I think we need to clearly describe what is the tread-safety policy in DPDK (especially in ethdev as a first example). Let's start with obvious things: 1/ A queue is not protected for races with multiple Rx or Tx - no planned change because of performance purpose 2/ The list of devices is racy - to be fixed with atomics 3/ The configuration of different devices is thread-safe - the configurations are different per-device 4/ The configuration of a given device is racy - can be managed by the owner of the device 5/ The device ownership is racy - to be fixed with atomics What am I missing? I am also wondering whether the device ownership can be a separate library used in several device class interfaces?