From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <yanmiaobest@gmail.com>
Received: from mail-it1-f169.google.com (mail-it1-f169.google.com
 [209.85.166.169]) by dpdk.org (Postfix) with ESMTP id 22F701B6EB
 for <users@dpdk.org>; Mon, 17 Dec 2018 10:12:10 +0100 (CET)
Received: by mail-it1-f169.google.com with SMTP id h193so18834011ita.5
 for <users@dpdk.org>; Mon, 17 Dec 2018 01:12:10 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025;
 h=mime-version:from:date:message-id:subject:to;
 bh=JHxcUiRv9iiVh6h1C12oEF8v/sFl2kGwTLcx4ZzutR0=;
 b=fK5fGVjd7tvhbkKknK0VmOVgkq0eYbsK6hKuDwET7QgY/+iRT1SDyfXk0appRs5Rf/
 j2zdbWFLSQtwNdLCUi2IsWEry6D9/u8gY05GRKWIpOJZIISi3OkfP21uUwePNlRJCzfI
 68DBkCYKW843QQbYYtUfqboTz+IomaQ4Haok68vrgVQdxm7idi+oLRmbMr+P2r3OKmkY
 DPMR7i7NkTSuCFTO/dtqa7DB9mxxnzegl8TjfJ5fQyrJwWW5EvlBzRt4ktt0urBk9Ucf
 tOK9EhWnesppBsgdc5h2XnNKldfng6yZmaqxVrX1mYjeZfPsaUlmO4Vip83O54tDE8la
 XYCA==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
 d=1e100.net; s=20161025;
 h=x-gm-message-state:mime-version:from:date:message-id:subject:to;
 bh=JHxcUiRv9iiVh6h1C12oEF8v/sFl2kGwTLcx4ZzutR0=;
 b=BxgQtdnuj2N17akYJay05GqimqsVhF3UPKysmG5i4tCQx3xpfEV3cQorAscVgOLWIh
 Gou5viGvCp6QxHYEuEuLqtCi+89klPGJRfg3hIz9PKiR45ktrTNd/nf7auQd5+Bsq/3w
 imm7TmCL+OKK/QbaojrKZIJBOl4nIINR7D2nSw0ADIixmiRKf7BeDkehJxUsHdNfe8Ck
 tUJ2gicCjyewrTb1bOH1rmnTxIee9Fw9sgPf0woWhA3F0KZ6zhslDY6yf9T4gTiu4rM6
 Xv2eCjjeqX9CUBKcyK8e6ntmHN5cWlA1ZWTLJm/leRVx5whkIkYHuolO2Jg5VOBZHl6q
 r4Nw==
X-Gm-Message-State: AA+aEWY0wK5f9D3GsXTtK/KM/Lz++YKoglwGoPlMEelOwSldF2rawbhy
 /U1fXOHeEcUujOq+fj7Di1mNZFPPyRNtmZeEzVdOd7Ux
X-Google-Smtp-Source: AFSGD/X/Mgb9XuRW1HYom1dCqH9jsCa1Aa8BsIuGdi4keif6mmshmLeTteST/kYj4NHlIDTsQpDCgdoBwNwUFkE4sss=
X-Received: by 2002:a24:7596:: with SMTP id y144mr12047444itc.68.1545037929261; 
 Mon, 17 Dec 2018 01:12:09 -0800 (PST)
MIME-Version: 1.0
From: Miao Yan <yanmiaobest@gmail.com>
Date: Mon, 17 Dec 2018 17:12:01 +0800
Message-ID: <CAPc5xaP3YLvhiNWKBkvz_ePnWJGkK05OUOEwPNRnWh1d9q4DHQ@mail.gmail.com>
To: users@dpdk.org
Content-Type: text/plain; charset="UTF-8"
Subject: [dpdk-users] Possible race in bonding driver ?
X-BeenThere: users@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: DPDK usage discussions <users.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/users>,
 <mailto:users-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/users/>
List-Post: <mailto:users@dpdk.org>
List-Help: <mailto:users-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/users>,
 <mailto:users-request@dpdk.org?subject=subscribe>
X-List-Received-Date: Mon, 17 Dec 2018 09:12:10 -0000

Hello Experts,

I am currently working on a project to implement a new team policy
based on the bonding driver. Basically, I have lots of 'ports', each of them
has a ID.  I'd like to use the ID to calculate the hash and distribute
the traffic to different slave ports, similar to round-robin, except
the sender ID
is fixed.

And when looking into bonding driver code, the following code looks like racy:

static uint16_t
bond_ethdev_tx_burst_round_robin(void *queue, struct rte_mbuf **bufs,
uint16_t nb_pkts)
{
...

/* Copy slave list to protect against slave up/down changes during tx
* bursting */
num_of_slaves = internals->active_slave_count;
memcpy(slaves, internals->active_slaves,
sizeof(internals->active_slaves[0]) * num_of_slaves);
[...]
}


void
deactivate_slave(struct rte_eth_dev *eth_dev, uint16_t port_id)
{
[...]
/* If slave was not at the end of the list
* shift active slaves up active array list */
if (slave_pos < active_count) {
    active_count--;
    memmove(internals->active_slaves + slave_pos,
                      internals->active_slaves + slave_pos + 1,
                      (active_count - slave_pos) *
                      sizeof(internals->active_slaves[0]));
 }
[...]
}

What if a core is dumping packets to the bond device and at the same time
a slave is down and another core is handling the deactivation (or it
could be just
another core calling rte_bond_slave_remove). It seems it's possible
for the TX core to see a partially updated  active_slaves array during memmove.

Is this a problem or am I missing something ? Thank you for the help.

Regards,
Miao