From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: Re: [v5 Patch 1/3] netpoll: add generic support for bridge and bonding devices Date: Mon, 31 May 2010 13:37:29 +0800 Message-ID: <4C034B19.10902@redhat.com> References: <20100505081514.5157.83783.sendpatchset@localhost.localdomain> <20100527180545.GA2345@sysclose.org> <4BFF7BE2.6020503@redhat.com> <20100528204229.GD2345@sysclose.org> <24802.1275080599@death.nxdomain.ibm.com> <4C03494B.1010802@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Flavio Leitner , linux-kernel@vger.kernel.org, Matt Mackall , netdev@vger.kernel.org, bridge@lists.linux-foundation.org, Andy Gospodarek , Neil Horman , Jeff Moyer , Stephen Hemminger , bonding-devel@lists.sourceforge.net, David Miller To: Jay Vosburgh Return-path: In-Reply-To: <4C03494B.1010802@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 05/31/10 13:29, Cong Wang wrote: > On 05/29/10 05:03, Jay Vosburgh wrote: >> Flavio Leitner wrote: >> >>> On Fri, May 28, 2010 at 04:16:34PM +0800, Cong Wang wrote: >>>> On 05/28/10 02:05, Flavio Leitner wrote: >>>>> >>>>> Hi guys! >>>>> >>>>> I finally could test this to see if an old problem reported on >>>>> bugzilla[1] was >>>>> fixed now, but unfortunately it is still there. >>>>> >>>>> The ticket is private I guess, but basically the problem happens >>>>> when bonding >>>>> driver tries to print something after it had taken the write_lock >>>>> (monitor >>>>> functions, enslave/de-enslave), so the printk() will pass through >>>>> netpoll, then >>>>> on bonding again which no matter what mode you use, it will try to >>>>> read_lock() >>>>> the lock again. The result is a deadlock and the entire system hangs. >>>>> >>>> >>>> Does the attached patch fix this hang? >>> >>> I got another issue now: >>> >>> [ 89.523062] bonding: bond0: enslaving eth0 as a backup interface >>> with a down link. >>> [ 89.580746] bonding: bond0: enslaving eth2 as a backup interface >>> with a down link. >>> [ 91.198527] e1000: eth2 NIC Link is Up 100 Mbps Half Duplex, Flow >>> Control: None >>> [ 91.238245] bonding: bond0: link status definitely up for interface >>> eth2. >>> >>> [ 91.245381] BUG: scheduling while atomic: bond0/2716/0x10000100 >>> [ 91.251565] 5 locks held by bond0/2716: >>> [ 91.255663] #0: ((bond_dev->name)){+.+.+.}, at: [] >>> worker_thread+0x19a/0x2e2 >>> [ 91.265179] #1: ((&(&bond->mii_work)->work)){+.+.+.}, at: >>> [] worker_thread+0x19a/0x2e2 >>> [ 91.275554] #2: (rtnl_mutex){+.+.+.}, at: [] >>> rtnl_lock+0x12/0x14 >>> [ 91.284018] #3: (&bond->lock){++.+.+}, at: [] >>> bond_mii_monitor+0x2a2/0x4ed [bonding] >>> [ 91.294230] #4: (&bond->curr_slave_lock){+...+.}, at: >>> [] bond_mii_monitor+0x471/0x4ed [bonding] >>> [ 91.305387] Modules linked in: bonding sunrpc ip6t_REJECT xt_tcpudp >>> nf_conntrack_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables >>> x_tables ipv6 dm_mirror dm_region_hash dm_log dm_multipath uinput >>> snd_hda_codec_idt snd_hda_intel snd_hda_codec snd_hwdep snd_seq >>> snd_seq_device snd_pcm ppdev parport_pc parport rtc_cmos snd_timer >>> tg3 snd ide_cd_mod i5000_edac i2c_i801 libphy rtc_core rtc_lib >>> edac_core pcspkr e1000 dcdbas uhci_hcd tulip shpchp i2c_core cdrom >>> serio_raw soundcore sg snd_page_alloc raid0 sd_mod button [last >>> unloaded: mperf] >>> [ 91.357735] Pid: 2716, comm: bond0 Not tainted >>> 2.6.34-04700-gd938a70-dirty #36 >>> [ 91.371112] Call Trace: >>> [ 91.373825] [] ? __debug_show_held_locks+0x22/0x24 >>> [ 91.380530] [] __schedule_bug+0x6d/0x72 >>> [ 91.386284] [] schedule+0xc9/0x791 >>> [ 91.391600] [] __cond_resched+0x25/0x30 >>> [ 91.397350] [] _cond_resched+0x27/0x32 >>> [ 91.403013] [] kmem_cache_alloc+0x2b/0xac >>> [ 91.408936] [] skb_clone+0x42/0x5d >>> [ 91.414253] [] netlink_broadcast+0x192/0x369 >>> [ 91.420436] [] nlmsg_notify+0x43/0x89 >>> [ 91.426012] [] rtnl_notify+0x2b/0x2d >>> [ 91.431501] [] rtmsg_ifinfo+0xf3/0x118 >>> [ 91.437165] [] rtnetlink_event+0x2b/0x2f >>> [ 91.443003] [] notifier_call_chain+0x32/0x5e >>> [ 91.449188] [] raw_notifier_call_chain+0xf/0x11 >>> [ 91.455634] [] call_netdevice_notifiers+0x45/0x4a >>> [ 91.462253] [] netdev_bonding_change+0x12/0x14 >> >> This warning is because the notifier call is happening with spin >> locks held. >> >>> [ 91.468614] [] bond_select_active_slave+0xe8/0x123 >>> [bonding] >>> [ 91.476408] [] bond_mii_monitor+0x479/0x4ed [bonding] >>> [ 91.483375] [] worker_thread+0x1ef/0x2e2 >>> [ 91.489212] [] ? worker_thread+0x19a/0x2e2 >>> [ 91.495227] [] ? bond_mii_monitor+0x0/0x4ed [bonding] >>> [ 91.502192] [] ? autoremove_wake_function+0x0/0x34 >>> [ 91.508897] [] ? worker_thread+0x0/0x2e2 >>> [ 91.514734] [] kthread+0x7a/0x82 >>> [ 91.519878] [] kernel_thread_helper+0x4/0x10 >>> [ 91.526060] [] ? restore_args+0x0/0x30 >>> [ 91.531723] [] ? kthread+0x0/0x82 >>> [ 91.536953] [] ? kernel_thread_helper+0x0/0x10 >>> [ 91.543343] bonding: bond0: making interface eth2 the new active one. >>> [ 91.550554] bonding: bond0: first active interface up! >>> [ 91.556859] ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready >>> >>> >>> No other patch applied. Just started netconsole over bonding, so no need >>> to pull the cable from slaves. Reproduced twice, one I got the >>> backtrace above, and on the other one the system hangs completely >>> after the BUG: scheduling message. >>> >>> fbl >>> >>> >>>> >>>> Thanks! >>>> >>>> -----------------------> >>>> >>>> We should notify netconsole that bond is changing its slaves >>>> when we use active-backup mode. >>>> >>>> Signed-off-by: WANG Cong >>>> >>>> ---- >>>> >>> >>>> diff --git a/drivers/net/bonding/bond_main.c >>>> b/drivers/net/bonding/bond_main.c >>>> index 5e12462..9494c02 100644 >>>> --- a/drivers/net/bonding/bond_main.c >>>> +++ b/drivers/net/bonding/bond_main.c >>>> @@ -1199,6 +1199,7 @@ void bond_select_active_slave(struct bonding >>>> *bond) >>>> >>>> best_slave = bond_find_best_slave(bond); >>>> if (best_slave != bond->curr_active_slave) { >>>> + netdev_bonding_change(bond->dev, NETDEV_BONDING_DESLAVE); >>>> bond_change_active_slave(bond, best_slave); >>>> rv = bond_set_carrier(bond); >>>> if (!rv) >> >> You can't do this here; the driver is holding various spin >> locks, and notifier calls can sleep (hence the warning). If you look at >> the bond_change_active_slave function, it drops all locks other than >> RTNL before making a notifier call, e.g., >> >> void bond_change_active_slave(struct bonding *bond, struct slave >> *new_active) >> { >> [...] >> if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) { >> [...] >> write_unlock_bh(&bond->curr_slave_lock); >> read_unlock(&bond->lock); >> >> netdev_bonding_change(bond->dev, NETDEV_BONDING_FAILOVER); >> >> read_lock(&bond->lock); >> write_lock_bh(&bond->curr_slave_lock); >> } >> >> >> You may be able to add your notifier to this case, or change >> your handler to notice the _FAILOVER notifier. > > > Thanks for your analysis! Hmm, I think let netconsole to handle > NETDEV_BONDING_FAILOVER here is a better solution. > No, in bond_change_active_slave() does notification after printing messages, thus will not solve the problem here, we need to notify netconsole before printing any messages. Thanks.