From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2A67C433B4 for ; Tue, 20 Apr 2021 03:22:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8EBF661360 for ; Tue, 20 Apr 2021 03:22:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233867AbhDTDXW (ORCPT ); Mon, 19 Apr 2021 23:23:22 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:16140 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229566AbhDTDXU (ORCPT ); Mon, 19 Apr 2021 23:23:20 -0400 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FPTSh5TwJzmdTc; Tue, 20 Apr 2021 11:19:48 +0800 (CST) Received: from [10.174.177.26] (10.174.177.26) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.498.0; Tue, 20 Apr 2021 11:22:41 +0800 Subject: Re: [PATCH] bonding: 3ad: update slave arr after initialize To: Jay Vosburgh CC: , , , , , , , , References: <1618537982-454-1-git-send-email-jinyiting@huawei.com> <17733.1618547307@famine> From: jin yiting Message-ID: <1165c45f-ae7f-48c1-5c65-a879c7bf978a@huawei.com> Date: Tue, 20 Apr 2021 11:22:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <17733.1618547307@famine> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.26] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/4/16 12:28, Jay Vosburgh 写道: > jinyiting wrote: > >> From: jin yiting >> >> The bond works in mode 4, and performs down/up operations on the bond >> that is normally negotiated. The probability of bond-> slave_arr is NULL >> >> Test commands: >> ifconfig bond1 down >> ifconfig bond1 up >> >> The conflict occurs in the following process： >> >> __dev_open (CPU A) >> --bond_open >> --queue_delayed_work(bond->wq,&bond->ad_work,0); >> --bond_update_slave_arr >> --bond_3ad_get_active_agg_info >> >> ad_work(CPU B) >> --bond_3ad_state_machine_handler >> --ad_agg_selection_logic >> >> ad_work runs on cpu B. In the function ad_agg_selection_logic, all >> agg->is_active will be cleared. Before the new active aggregator is >> selected on CPU B, bond_3ad_get_active_agg_info failed on CPU A, >> bond->slave_arr will be set to NULL. The best aggregator in >> ad_agg_selection_logic has not changed, no need to update slave arr. >> >> Signed-off-by: jin yiting >> --- >> drivers/net/bonding/bond_3ad.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c >> index 6908822..d100079 100644 >> --- a/drivers/net/bonding/bond_3ad.c >> +++ b/drivers/net/bonding/bond_3ad.c >> @@ -2327,6 +2327,12 @@ void bond_3ad_state_machine_handler(struct work_struct *work) >> >> aggregator = __get_first_agg(port); >> ad_agg_selection_logic(aggregator, &update_slave_arr); >> + if (!update_slave_arr) { >> + struct aggregator *active = __get_active_agg(aggregator); >> + >> + if (active && active->is_active) >> + update_slave_arr = true; >> + } >> } >> bond_3ad_set_carrier(bond); >> } > > The described issue is a race condition (in that > ad_agg_selection_logic clears agg->is_active under mode_lock, but > bond_open -> bond_update_slave_arr is inspecting agg->is_active outside > the lock). I don't see how the above change will reliably manage this; > the real issue looks to be that bond_update_slave_arr is committing > changes to the array (via bond_reset_slave_arr) based on a racy > inspection of the active aggregator state while it is in flux. > > Also, the description of the issue says "The best aggregator in > ad_agg_selection_logic has not changed, no need to update slave arr," > but the change above does the opposite, and will set update_slave_arr > when the aggregator has not changed (update_slave_arr remains false at > return of ad_agg_selection_logic). > > I believe I understand the described problem, but I don't see > how the patch fixes it. I suspect (but haven't tested) that the proper > fix is to acquire mode_lock in bond_update_slave_arr while calling > bond_3ad_get_active_agg_info to avoid conflict with the state machine. > > -J > > --- > -Jay Vosburgh, jay.vosburgh@canonical.com > . > Thank you for your reply. The last patch does have redundant update slave arr.Thank you for your correction. As you said, holding mode_lock in bond_update_slave_arr while calling bond_3ad_get_active_agg_info can avoid conflictwith the state machine. I have tested this patch, with ifdown/ifup operations for bond or slaves. But bond_update_slave_arr is expected to hold RTNL only and NO other lock. And it have WARN_ON(lockdep_is_held(&bond->mode_lock)); in bond_update_slave_arr. I'm not sure that holding mode_lock in bond_update_slave_arr while calling bond_3ad_get_active_agg_info is a correct action. diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 74cbbb2..db988e5 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -4406,7 +4406,9 @@ int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave) if (BOND_MODE(bond) == BOND_MODE_8023AD) { struct ad_info ad_info; + spin_lock_bh(&bond->mode_lock); if (bond_3ad_get_active_agg_info(bond, &ad_info)) { + spin_unlock_bh(&bond->mode_lock); pr_debug("bond_3ad_get_active_agg_info failed\n"); /* No active aggragator means it's not safe to use * the previous array. @@ -4414,6 +4416,7 @@ int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave) bond_reset_slave_arr(bond); goto out; } + spin_unlock_bh(&bond->mode_lock); agg_id = ad_info.aggregator_id; } bond_for_each_slave(bond, slave, iter) {