From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chas Williams <3chas3@gmail.com> Subject: Re: =?utf-8?b?562U5aSNOiAgW1BBVENIXSBuZXQvYm9uZGluZzogZml4?= =?utf-8?q?_double_fetch_for_active=5Fslave=5Fcount?= Date: Fri, 30 Nov 2018 17:28:09 -0500 Message-ID: <54d81172-c5df-44b9-27ea-2ce03adc8604@gmail.com> References: <1543469561-8864-1-git-send-email-haifeng.lin@huawei.com> <8fdfaff2-8f59-8d4b-db6c-a8a3c26fb4e2@gmail.com> <4099DE2E54AFAD489356C6C9161D5333958924EF@DGGEML502-MBS.china.huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: "chas3@att.com" To: Linhaifeng , "dev@dpdk.org" Return-path: Received: from mail-qt1-f193.google.com (mail-qt1-f193.google.com [209.85.160.193]) by dpdk.org (Postfix) with ESMTP id E59011B5C9 for ; Fri, 30 Nov 2018 23:28:11 +0100 (CET) Received: by mail-qt1-f193.google.com with SMTP id p17so7697136qtl.5 for ; Fri, 30 Nov 2018 14:28:11 -0800 (PST) In-Reply-To: <4099DE2E54AFAD489356C6C9161D5333958924EF@DGGEML502-MBS.china.huawei.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" The problem is that I can't see how the API can ever provide accurate information. By the time you have the information it is potentially stale. There really isn't a way to control if a slave is active since that is protocol dependent. rte_eth_bond_slaves_get() is safer in the sense that you control when the slaves are added and removed from the bonding group. You can ensure that you get a consistent answer. Hopefully your protocol doesn't especially care if the slave is active or not. You are sending the packets via rte_eth_bond_8023ad_ext_slow()? On 11/30/18 12:50 AM, Linhaifeng wrote: > Hi, Chars > > Thank you. > > I use it for send pkts to the dedicated queue of slaves. > > Maybe i should not use it. I would though another way. > > -----邮件原件----- > 发件人: Chas Williams [mailto:3chas3@gmail.com] > 发送时间: 2018年11月30日 11:27 > 收件人: Linhaifeng ; dev@dpdk.org > 抄送: chas3@att.com > 主题: Re: [dpdk-dev] [PATCH] net/bonding: fix double fetch for active_slave_count > > I guess this is slightly more correct. There is still a race here though. > After you make your copy of active_slave_count, the number of active slaves could go to 0 and the memcpy() would copy an invalid element, acitve_slaves[0]. There is no simple fix to this problem. Your patch reduces the opportunity for a race but doesn't eliminate it. > > What you are using this API for? > > On 11/29/18 12:32 AM, Haifeng Lin wrote: >> 1. when memcpy slaves the internals->active_slave_count 1 2. return >> internals->active_slave_count is 2 3. the slaves[1] would be a random >> invalid value >> >> Signed-off-by: Haifeng Lin >> --- >> drivers/net/bonding/rte_eth_bond_api.c | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/net/bonding/rte_eth_bond_api.c >> b/drivers/net/bonding/rte_eth_bond_api.c >> index 21bcd50..ed7b02e 100644 >> --- a/drivers/net/bonding/rte_eth_bond_api.c >> +++ b/drivers/net/bonding/rte_eth_bond_api.c >> @@ -815,6 +815,7 @@ >> uint16_t len) >> { >> struct bond_dev_private *internals; >> + uint16_t active_slave_count; >> >> if (valid_bonded_port_id(bonded_port_id) != 0) >> return -1; >> @@ -824,13 +825,14 @@ >> >> internals = rte_eth_devices[bonded_port_id].data->dev_private; >> >> - if (internals->active_slave_count > len) >> + active_slave_count = internals->active_slave_count; >> + if (active_slave_count > len) >> return -1; >> >> memcpy(slaves, internals->active_slaves, >> - internals->active_slave_count * sizeof(internals->active_slaves[0])); >> + active_slave_count * sizeof(internals->active_slaves[0])); >> >> - return internals->active_slave_count; >> + return active_slave_count; >> } >> >> int >>