From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <gaetan.rivet@6wind.com> Received: from mail-wm1-f66.google.com (mail-wm1-f66.google.com [209.85.128.66]) by dpdk.org (Postfix) with ESMTP id 394562B87 for <dev@dpdk.org>; Thu, 7 Mar 2019 12:50:42 +0100 (CET) Received: by mail-wm1-f66.google.com with SMTP id x7so8993854wmj.0 for <dev@dpdk.org>; Thu, 07 Mar 2019 03:50:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=6wind-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=mrV9X0J+3d8P8r68WdnBrKicwA5D4pyplgrvQvwnayo=; b=vJxToczbArPwTewgF1eVxIZCaU/mJfMe0E2X02PMmexD6ehsdyquscXZrra1JQb0/C TrFqZV80BunXkq4Tg7PmTb/Hcb0VOPB84iaAqJk9SckQuo1K1q4/Z4bN0SxFgDDndNRI Zr6n3w1/8drz0eF0po7GUcScktfWU/XjkqhfEmdkvoxyLfuSL1gXu+IqFHSQyqk9QjjR RM0foiOyPVc0Q4vhH2foY10MJh8Ma0YCmpjZFsihMHb43I3ad4ax7go7aJbONkiUs5Ez 9mMrmwmfSp6h5QtE9IEUAlo3hzDn8rpBbHh1qyq9oHkTle1bwMLaIK2WKK/YgGSmcc6J X8Nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=mrV9X0J+3d8P8r68WdnBrKicwA5D4pyplgrvQvwnayo=; b=Jj5eAPp/OvBZ/RKgjcocr1vz9Szro2etW46xNnv+rWFM0X0SzI9ncAhmKzQdbVFj4Y t67KyfWm3LT02DSRJTUypU4Ok/4RXtpfRFRq+X66VkkwyHl/iaaD5/vzInYVPSiue6VJ mqf2p7Vxf60zTpVVx2eHm32i4/0UYgDkjthrfrbzRADhHj0bVIxI7KY2Seo/ll7zplrn PO4UJc4ZYkDG71tgDKbAJdlW/9J4deKgDmKIdrYhmF9Qd5MTbmRoUB8nZt2r1IbrbsW4 AU3+0GWNLC3Q9bOSBRmbOut1lDi36RRHOlqn4T0mNTaPJdc41v9YlISzp/nnGVsvxEtn 8ESQ== X-Gm-Message-State: APjAAAWGw4aJdWdSNNQNRhfnyfaYILo771MgchZRnTjo46iv+5H6SHlX hFiMuMbBTeQL5EDOwXcmuGrwag== X-Google-Smtp-Source: APXvYqyAdf6CRuclcr7BgCsmWKRhkaP15f5bSDesPXamDUkDJXM3aSz5jwC769rrHtB/68FuTFGdBA== X-Received: by 2002:a1c:a186:: with SMTP id k128mr5382023wme.54.1551959441593; Thu, 07 Mar 2019 03:50:41 -0800 (PST) Received: from bidouze.vm.6wind.com (host.78.145.23.62.rev.coltfrance.com. [62.23.145.78]) by smtp.gmail.com with ESMTPSA id p5sm4777171wme.14.2019.03.07.03.50.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 07 Mar 2019 03:50:40 -0800 (PST) Date: Thu, 7 Mar 2019 12:50:38 +0100 From: =?iso-8859-1?Q?Ga=EBtan?= Rivet <gaetan.rivet@6wind.com> To: Raslan Darawsheh <rasland@mellanox.com> Cc: Thomas Monjalon <thomas@monjalon.net>, "dev@dpdk.org" <dev@dpdk.org>, "stephen@networkplumber.org" <stephen@networkplumber.org> Message-ID: <20190307115038.rwomp3jlcxikhj5y@bidouze.vm.6wind.com> References: <1551779507-10857-1-git-send-email-rasland@mellanox.com> <172443910.dRk5910QrU@xps> <20190306104632.fia2r2sz5yajvkne@bidouze.vm.6wind.com> <6541291.VHOuPfexjb@xps> <AM6PR05MB59265B8B39776EE53753BE26C24C0@AM6PR05MB5926.eurprd05.prod.outlook.com> <20190307094757.56db3w74ftqkra7d@bidouze.vm.6wind.com> <AM6PR05MB59269CF2F1AE80B0635E3836C24C0@AM6PR05MB5926.eurprd05.prod.outlook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <AM6PR05MB59269CF2F1AE80B0635E3836C24C0@AM6PR05MB5926.eurprd05.prod.outlook.com> User-Agent: NeoMutt/20170113 (1.7.2) Subject: Re: [dpdk-dev] [PATCH v2 3/4] net/failsafe: replace local sub-device with shared data X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Thu, 07 Mar 2019 11:50:42 -0000 On Thu, Mar 07, 2019 at 11:34:42AM +0000, Raslan Darawsheh wrote: > Hi, > > > -----Original Message----- > > From: Gaëtan Rivet <gaetan.rivet@6wind.com> > > Sent: Thursday, March 7, 2019 11:48 AM > > To: Raslan Darawsheh <rasland@mellanox.com> > > Cc: Thomas Monjalon <thomas@monjalon.net>; dev@dpdk.org; > > stephen@networkplumber.org > > Subject: Re: [dpdk-dev] [PATCH v2 3/4] net/failsafe: replace local sub-device > > with shared data > > > > On Thu, Mar 07, 2019 at 08:43:01AM +0000, Raslan Darawsheh wrote: > > > Hi, > > > > > > > -----Original Message----- > > > > From: Thomas Monjalon <thomas@monjalon.net> > > > > Sent: Wednesday, March 6, 2019 8:02 PM > > > > To: Gaëtan Rivet <gaetan.rivet@6wind.com>; Raslan Darawsheh > > > > <rasland@mellanox.com> > > > > Cc: dev@dpdk.org; stephen@networkplumber.org > > > > Subject: Re: [dpdk-dev] [PATCH v2 3/4] net/failsafe: replace local > > > > sub-device with shared data > > > > > > > > 06/03/2019 11:46, Gaëtan Rivet: > > > > > On Tue, Mar 05, 2019 at 06:58:04PM +0100, Thomas Monjalon wrote: > > > > > > 05/03/2019 18:38, Gaëtan Rivet: > > > > > > > What happens when a primary process closes a device before a > > > > secondary? > > > > > > > Is the secondary unable to stop / close its own then? Isn't > > > > > > > there some missing uninit? > > > > > > > > > > > > Is the secondary process supposed to do any closing? > > > > > > The device management should be done only by the primary process. > > > > > > > > > > > > Note: anyway all this hotplug related code should be dropped > > > > > > from failsafe to be replaced by EAL hotplug management. > > > > > > > > > > > > > > > > I don't know, I've never used secondary process. > > > > > However, cursory reading the code of rte_eth_dev_close(), I don't > > > > > see a guard against calling it from a secondary process? > > > > > > > > Yes indeed, there is no guard. > > > > That's something not clear in DPDK, previously we were attaching > > > > some vdevs in secondary only. > > > > > > > > > Reading code like > > > > > > > > > > rte_free(dev->data->rx_queues); > > > > > dev->data->rx_queues = NULL; > > > > > > > > > > within makes me think the issue has been seen at least once, where > > > > > shared data is freed multiple times, so I guessed some secondary > > > > > processes were calling it. Maybe they are not meant to, but what > > > > > prevents them from being badly written? > > > > > > > > > > Also, given rte_dev_remove IPC call to transfer the order to the > > > > > primary, it seems that at least secondary processes are expected > > > > > to call > > > > > rte_dev_remove() at some point? So are they only authorized to > > > > > call > > > > > rte_dev_remove() (to manage hotplug), but not rte_eth_dev_close()? > > > > > Is there a specific documentation detailing the design of > > > > > secondary process and the related responsibilities in the lifetime of a > > device? > > > > > How are they synching their rte_eth_devices list if they are not > > > > > calling rte_eth_dev_close(), ever? > > > > > > > > All these calls should be done in primary. > > > > The IPC mechanism calls the attach/detach in secondary at EAL level. > > > > The PMDs does the bridge between EAL device and ethdev port status. > > > > But you are right, there can be a sync issue if closing an ethdev > > > > port and not removing the EAL device. > > > > This is a generic question about deciding whether we want all ethdev > > > > ports to be synced in multi-process or not. > > > > > > > > In failsafe context, we are closing the EAL device and change the > > > > state of the sub-device accordingly. So I think there is no issue. > > > > > > > > > > > This seems dangerous to me. Why not instead allocating a > > > > > > > per-process slab of memory that would hold the relevant > > > > > > > references and outlive the shared data (a per-process rte_eth_dev > > private data...). > > > > > > > > > > > > Which data do you think should be allocated per process? > > > > > > > > > > > > > > > > > > > > > > [-------- SHARED SPACE --------------] [-- PER-PROCESS --------] > > > > > +--------------------------------------------------------------+ > > > > > | +------------------+ +- rte_eth_devices[n] -+ | > > > > > | |rte_eth_dev_data |<---------------+ data | | PRIMARY > > > > > | | | +dev_priv-+ | | | > > > > > | | dev_private +-->| | | | | > > > > > | | ... | | | | | | > > > > > | | port_id | | | | | | > > > > > | | | | | | | | > > > > > | | | | | | | | > > > > > | | | | | +----------------------+ | > > > > > | | | | | +- rte_eth_devices[n] -+ | > > > > > | | | | | | | | SECONDARY > > > > > | | | | | | | | > > > > > | | | | | | | | > > > > > | | | | | | | | > > > > > | | | +---------+ | | | > > > > > | | |<---------------+ data | | > > > > > | +------------------+ +----------------------+ | > > > > > +--------------------------------------------------------------+ > > > > > > > > > > Here port_id is used within fail-safe to get back to rte_eth_devices[n]. > > > > > This disappears once a device is closed, as all shared space is zeroed. > > > > > > > > > > This means that sometimes ETH(sdev) and PORT_ID(sdev) is correct, > > > > > and at some point it is not anymore, once a sub-device has been closed. > > > > > This seems dangerous. > > > > > > > > The state of the sub-device is changed. > > > > I don't see any issue. > > > > > > > > > I was thinking initially that allocating a place where each sdev > > > > > would store their rte_eth_devices / port_id back-reference could > > > > > alleviate the issue, meaning that the fail-safe would not zero it > > > > > on sdev_close(), and it would remain valid for the lifetime of a > > > > > sub-device, so even when a sub-device is in DEV_PROBED state. > > > > > > > > > > But now that I think about it, it could probably be simpler: > > > > > instead of using (ETH(sdev)->data->port_id) for the port_id of an > > > > > sdev (meaning that it is dependent on the lifetime of the sdev, > > > > > instead of the lifetime of the failsafe), the port-id itself > > > > > should be stored in the sub_device structure. This structure will > > > > > be available for the lifetime of the failsafe, and the port_id is correct > > accross all processes. > > > > > > > > > > So PORT_ID(sdev) would be defined to something like > > > > > (sdev->port_id), and > > > > > ETH(sdev) would be (&rte_eth_devices[PORT_ID(sdev)]). It would > > > > > remain correct even once the primary has closed the sub-device. > > > > > > > > > > What do you think? Do you agree that the current state is > > > > > dangerous, and do you think the solution would alleviate the > > > > > issue? Maybe the concern is unfounded and the only issue is within > > fs_dev_remove(). > > > > > > > > Yes it is only seen in fs_dev_remove(). > > > > I discussed about your proposal with Raslan, and we agree we could > > > > change from sub_device.data to sub_device.port_id, it may be more > > future-proof. > > > > > > > > I have only one doubt: look at the macro in this patch: > > > > > > > > #define ETH(sdev) \ > > > > ((sdev)->data == NULL ? NULL : &rte_eth_devices[(sdev)->data- > > > > >port_id]) > > > > > > > > The NULL check cannot be done with a port id. > > > > I think it was needed to manage one case. Raslan? > > > > > > That's right since we need it for fs_tx_unsafe, to add a protection for > > plugged out devices during TX. > > > > Ok, thanks for your insights Thomas and Raslan. Sorry about the rambling > > above I needed to write down the stuff to think about it. > > > > You can use RTE_MAX_ETHPORTS as a sentinel value for port_id, this way the > > value is kept unsigned and there are several checks against this specific value > > otherwise. > > > > so ETH(sdev) could be > > > > (PORT_ID(sdev) >= RTE_MAX_ETHPORTS ? NULL : > > &rte_eth_devices[PORT_ID(sdev)]) > > > But, this mean that you have to explicitly set the port id to RTE_MAX_ETH_PORTS in the sdev after fs_dev_remove and you shouldn't rely on the port ID anymore. > Yes, once a sub-device has completely finished its removal (from the fail-safe PoV), the fail-safe marks the sub-device as not used anymore. This seems correct. If the fail-safe used the sdev->data->port_id instead, it would return 0, which is a valid port_id that is probably still used by another port. > > -- > > > Gaëtan Rivet > > 6WIND > > Kindest regards > Raslan Darawsheh -- Gaëtan Rivet 6WIND