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 12:53:46 +0100 Message-ID: <530349CA.9070209@redhat.com> References: <53034312.1060203@huawei.com> <530348C4.4050408@redhat.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]:62531 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752047AbaBRLyK (ORCPT ); Tue, 18 Feb 2014 06:54:10 -0500 In-Reply-To: <530348C4.4050408@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 02/18/2014 12:49 PM, Nikolay Aleksandrov wrote: > 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 > Ah, missed where it gets updated, never mind this comment, it's fine.