From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikolay Aleksandrov Subject: Re: [PATCH net-next] bonding: Fix RTNL: assertion failed at net/core/rtnetlink.c for 802.3ad mode Date: Tue, 18 Feb 2014 12:49:24 +0100 Message-ID: <530348C4.4050408@redhat.com> References: <53034312.1060203@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit To: Ding Tianhong , Jay Vosburgh , Andy Gospodarek , Veaceslav Falico , Cong Wang , Thomas Glanzmann , Jiri Pirko , "David S. Miller" , Eric Dumazet , Scott Feldman , Netdev Return-path: Received: from mx1.redhat.com ([209.132.183.28]:15141 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753897AbaBRLuN (ORCPT ); Tue, 18 Feb 2014 06:50:13 -0500 In-Reply-To: <53034312.1060203@huawei.com> Sender: netdev-owner@vger.kernel.org List-ID: On 02/18/2014 12:25 PM, Ding Tianhong wrote: > The problem was introduced by the commit 1d3ee88ae0d > (bonding: add netlink attributes to slave link dev). > The bond_set_active_slave() and bond_set_backup_slave() > will use rtmsg_ifinfo to send slave's states, so these > two functions should be called in RTNL. > > In 802.3ad mode, acquiring RTNL for the __enable_port and > __disable_port cases is difficult, as those calls generally > already hold the state machine lock, and cannot unconditionally > call rtnl_lock because either they already hold RTNL (for calls > via bond_3ad_unbind_slave) or due to the potential for deadlock > with bond_3ad_adapter_speed_changed, bond_3ad_adapter_duplex_changed, > bond_3ad_link_change, or bond_3ad_update_lacp_rate. All four of > those are called with RTNL held, and acquire the state machine lock > second. The calling contexts for __enable_port and __disable_port > already hold the state machine lock, and may or may not need RTNL. > > According to the Jay's opinion, I don't think it is a problem that > the slave don't send notify message synchronously when the status > changed, normally the state machine is running every 100 ms, send > the notify message at the end of the state machine if the slave's > state changed should be better. > > I fix the problem through these steps: > > 1). add a new function bond_set_slave_state() which could change > the slave's state and call rtmsg_ifinfo() according to the input > parameters called notify. > > 2). Add a new slave parameter which called should_notify, if the slave's state > changed and don't notify yet, the parameter will be set to 1, and then if > the slave's state changed again, the param will be set to 0, it indicate that > the slave's state has been restored, no need to notify any one. > > 3). the __enable_port and __disable_port should not call rtmsg_ifinfo > in the state machine lock, any change in the state of slave could > set a flag in the slave, it will indicated that an rtmsg_ifinfo > should be called at the end of the state machine. > > Cc: Jay Vosburgh > Cc: Veaceslav Falico > Cc: Andy Gospodarek > Signed-off-by: Ding Tianhong > --- Hi Ding, I think there's a possible race condition which could lead to inconsistent state because you set slave->should_notify to 0 under RTNL but __disable_port can update it without RTNL e.g. can be called via bond_3ad_state_machine_handler -> ad_agg_selection_logic so in theory (I haven't tested it) they can execute concurrently. This is not a big deal though, but it would make this kind of message unreliable. Nik