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Date: Wed, 28 Jul 2021 10:42:12 +0300 From: Nikolay Aleksandrov <nikolay@...dia.com> To: Yufeng Mo <moyufeng@...wei.com>, davem@...emloft.net, kuba@...nel.org, jay.vosburgh@...onical.com, jiri@...nulli.us Cc: netdev@...r.kernel.org, shenjian15@...wei.com, lipeng321@...wei.com, yisen.zhuang@...wei.com, linyunsheng@...wei.com, zhangjiaran@...wei.com, huangguangbin2@...wei.com, chenhao288@...ilicon.com, salil.mehta@...wei.com, linuxarm@...wei.com, linuxarm@...neuler.org Subject: Re: [PATCH net-next] bonding: 3ad: fix the concurrency between __bond_release_one() and bond_3ad_state_machine_handler() On 28/07/2021 10:34, Nikolay Aleksandrov wrote: > On 28/07/2021 09:19, Yufeng Mo wrote: >> Some time ago, I reported a calltrace issue >> "did not find a suitable aggregator", please see[1]. >> After a period of analysis and reproduction, I find >> that this problem is caused by concurrency. >> >> Before the problem occurs, the bond structure is like follows: >> >> bond0 - slaver0(eth0) - agg0.lag_ports -> port0 - port1 >> \ >> port0 >> \ >> slaver1(eth1) - agg1.lag_ports -> NULL >> \ >> port1 >> >> If we run 'ifenslave bond0 -d eth1', the process is like below: >> >> excuting __bond_release_one() >> | >> bond_upper_dev_unlink()[step1] >> | | | >> | | bond_3ad_lacpdu_recv() >> | | ->bond_3ad_rx_indication() >> | | spin_lock_bh() >> | | ->ad_rx_machine() >> | | ->__record_pdu()[step2] >> | | spin_unlock_bh() >> | | | >> | bond_3ad_state_machine_handler() >> | spin_lock_bh() >> | ->ad_port_selection_logic() >> | ->try to find free aggregator[step3] >> | ->try to find suitable aggregator[step4] >> | ->did not find a suitable aggregator[step5] >> | spin_unlock_bh() >> | | >> | | >> bond_3ad_unbind_slave() | >> spin_lock_bh() >> spin_unlock_bh() >> >> step1: already removed slaver1(eth1) from list, but port1 remains >> step2: receive a lacpdu and update port0 >> step3: port0 will be removed from agg0.lag_ports. The struct is >> "agg0.lag_ports -> port1" now, and agg0 is not free. At the >> same time, slaver1/agg1 has been removed from the list by step1. >> So we can't find a free aggregator now. >> step4: can't find suitable aggregator because of step2 >> step5: cause a calltrace since port->aggregator is NULL >> >> To solve this concurrency problem, the range of bond->mode_lock >> is extended from only bond_3ad_unbind_slave() to both >> bond_upper_dev_unlink() and bond_3ad_unbind_slave(). >> >> [1]https://lore.kernel.org/netdev/10374.1611947473@famine/ >> >> Signed-off-by: Yufeng Mo <moyufeng@...wei.com> >> Acked-by: Jay Vosburgh <jay.vosburgh@...onical.com> >> --- >> drivers/net/bonding/bond_3ad.c | 7 +------ >> drivers/net/bonding/bond_main.c | 6 +++++- >> 2 files changed, 6 insertions(+), 7 deletions(-) >> > [snip] > after netdev_rx_handler_unregister() the bond's recv_probe cannot be executed > so you don't really need to unlink it under mode_lock or move mode_lock at all ^^^^ Forget this part of the comment, I saw later that you don't want to receive lacpdu on the other port The notifier sleep problem still exists though. > >> if (BOND_MODE(bond) == BOND_MODE_8023AD) >> bond_3ad_unbind_slave(slave); >> + spin_unlock_bh(&bond->mode_lock); >> >> if (bond_mode_can_use_xmit_hash(bond)) >> bond_update_slave_arr(bond, slave); >> >
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