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SubjectRe: [v5 Patch 1/3] netpoll: add generic support for bridge and bonding devices
On 05/29/10 05:03, Jay Vosburgh wrote:
> Flavio Leitner<fbl@sysclose.org> 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: [<ffffffff81045fb4>] worker_thread+0x19a/0x2e2
>> [ 91.265179] #1: ((&(&bond->mii_work)->work)){+.+.+.}, at: [<ffffffff81045fb4>] worker_thread+0x19a/0x2e2
>> [ 91.275554] #2: (rtnl_mutex){+.+.+.}, at: [<ffffffff812daf38>] rtnl_lock+0x12/0x14
>> [ 91.284018] #3: (&bond->lock){++.+.+}, at: [<ffffffffa029e06a>] bond_mii_monitor+0x2a2/0x4ed [bonding]
>> [ 91.294230] #4: (&bond->curr_slave_lock){+...+.}, at: [<ffffffffa029e239>] 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] [<ffffffff81056002>] ? __debug_show_held_locks+0x22/0x24
>> [ 91.380530] [<ffffffff8102e4a2>] __schedule_bug+0x6d/0x72
>> [ 91.386284] [<ffffffff81363f6e>] schedule+0xc9/0x791
>> [ 91.391600] [<ffffffff81032540>] __cond_resched+0x25/0x30
>> [ 91.397350] [<ffffffff81364757>] _cond_resched+0x27/0x32
>> [ 91.403013] [<ffffffff810ab243>] kmem_cache_alloc+0x2b/0xac
>> [ 91.408936] [<ffffffff812c61fd>] skb_clone+0x42/0x5d
>> [ 91.414253] [<ffffffff812ec696>] netlink_broadcast+0x192/0x369
>> [ 91.420436] [<ffffffff812ecdc3>] nlmsg_notify+0x43/0x89
>> [ 91.426012] [<ffffffff812dabc7>] rtnl_notify+0x2b/0x2d
>> [ 91.431501] [<ffffffff812dacbc>] rtmsg_ifinfo+0xf3/0x118
>> [ 91.437165] [<ffffffff812dad0c>] rtnetlink_event+0x2b/0x2f
>> [ 91.443003] [<ffffffff81369fe4>] notifier_call_chain+0x32/0x5e
>> [ 91.449188] [<ffffffff8104d618>] raw_notifier_call_chain+0xf/0x11
>> [ 91.455634] [<ffffffff812cfc73>] call_netdevice_notifiers+0x45/0x4a
>> [ 91.462253] [<ffffffff812d04f7>] netdev_bonding_change+0x12/0x14
>
> This warning is because the notifier call is happening with spin
> locks held.
>
>> [ 91.468614] [<ffffffffa029d589>] bond_select_active_slave+0xe8/0x123 [bonding]
>> [ 91.476408] [<ffffffffa029e241>] bond_mii_monitor+0x479/0x4ed [bonding]
>> [ 91.483375] [<ffffffff81046009>] worker_thread+0x1ef/0x2e2
>> [ 91.489212] [<ffffffff81045fb4>] ? worker_thread+0x19a/0x2e2
>> [ 91.495227] [<ffffffffa029ddc8>] ? bond_mii_monitor+0x0/0x4ed [bonding]
>> [ 91.502192] [<ffffffff81049c71>] ? autoremove_wake_function+0x0/0x34
>> [ 91.508897] [<ffffffff81045e1a>] ? worker_thread+0x0/0x2e2
>> [ 91.514734] [<ffffffff810498bb>] kthread+0x7a/0x82
>> [ 91.519878] [<ffffffff81003714>] kernel_thread_helper+0x4/0x10
>> [ 91.526060] [<ffffffff81366ffc>] ? restore_args+0x0/0x30
>> [ 91.531723] [<ffffffff81049841>] ? kthread+0x0/0x82
>> [ 91.536953] [<ffffffff81003710>] ? 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<amwang@redhat.com>
>>>
>>> ----
>>>
>>
>>> 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.

>
>>> @@ -2154,6 +2155,7 @@ static int bond_ioctl_change_active(struct net_device *bond_dev, struct net_devi
>>> (old_active)&&
>>> (new_active->link == BOND_LINK_UP)&&
>>> IS_UP(new_active->dev)) {
>>> + netdev_bonding_change(bond->dev, NETDEV_BONDING_DESLAVE);
>>> write_lock_bh(&bond->curr_slave_lock);
>>> bond_change_active_slave(bond, new_active);
>>> write_unlock_bh(&bond->curr_slave_lock);
>
> This case will have the same problem, but will only be hit if a
> user does a manual "ifenslave -c bond0 ethX".
>
> You also probably wanted to do the sysfs path, but if the
> notifier goes into the change_active_slave function itself, then I don't
> think additional notifications would be necessary.
>

Okay, sounds above solution should also handle this case.

Thanks.



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