linux-kernel - Re: [v2 Patch 3/3] bonding: make bonding support netpoll

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Date:	Wed, 07 Apr 2010 12:20:33 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Andy Gospodarek <andy@...yhouse.net>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Matt Mackall <mpm@...enic.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"bridge@...ts.linux-foundation.org" 
	<bridge@...ts.linux-foundation.org>,
	Andy Gospodarek <gospo@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	"bonding-devel@...ts.sourceforge.net" 
	<bonding-devel@...ts.sourceforge.net>,
	Jay Vosburgh <fubar@...ibm.com>,
	David Miller <davem@...emloft.net>
Subject: Re: [v2 Patch 3/3] bonding: make bonding support netpoll

Andy Gospodarek wrote:
> On Apr 6, 2010, at 10:32 PM, Cong Wang <amwang@...hat.com> wrote:
> 
>> Andy Gospodarek wrote:
>>> On Tue, Apr 06, 2010 at 12:38:16PM +0800, Cong Wang wrote:
>>>> Cong Wang wrote:
>>>>> Before I try to reproduce it, could you please try to replace
>>>>> the  'read_lock()'
>>>>> in slaves_support_netpoll() with 'read_lock_bh()'? (read_unlock()
>>>>> too)  Try if this helps.
>>>>>
>>>> Confirmed. Please use the attached patch instead, for your testing.
>>>>
>>>> Thanks!
>>>>
>>> Moving those locks to bh-locks will not resolve this.  I tried that
>>> yesterday and tried your new patch today without success.  That
>>> warning
>>> is a WARN_ON_ONCE so you need to reboot to see that it is still a
>>> problem.  Simply unloading and loading the new module is not an
>>> accurate
>>> test.
>>> Also, my system still hangs when removing the bonding module.  I do
>>> not
>>> think you intended to fix this with the patch, but wanted it to be
>>> clear
>>> to everyone on the list.
>>
>> Actually I did reboot and then tested the module. I didn't get any
>> warning.
>> I just tried again today, and no warnings at all.
>>
>> For removing bonding module, you may need another fix of mine,
>> which is to fix a potential deadlock of workqueue. Try:
>>
>> http://lkml.org/lkml/2010/4/1/58
>>
>>> You should also configure your kernel with a some of the lock
>>> debugging
>>> enabled.  I've been using the following:
>>> CONFIG_DETECT_HUNG_TASK=y
>>> CONFIG_DEBUG_SPINLOCK=y
>>> CONFIG_DEBUG_MUTEXES=y
>>> CONFIG_DEBUG_LOCK_ALLOC=y
>>> CONFIG_PROVE_LOCKING=y
>>> CONFIG_LOCKDEP=y
>>> CONFIG_LOCK_STAT=y
>>> CONFIG_DEBUG_LOCKDEP=y
>>
>> Sure, I always keep these.
>>
>>> Here is the output when I remove a slave from the bond.  My
>>> xmit_roundrobin patch from earlier (replacing read_lock with
>>> read_trylock) was applied.  It might be helpful for you when
>>> debugging
>>> these issues.
>>
>> I don't apply your patch, just tested my patch.
>>
>>> Dead loop on virtual device bond0, fix it urgently!
>> Please provide your bonding configuration and steps to reproduce it.
>>
> 
> My first response in this thread provides the commands and
> configuration needed to reproduce this.


Then I should do the right thing.

> 
>> What I did is:
>>
>> 1. Load bonding module with "mode=0 miimon=100"
>> 2. Enslave eth0 and active bond0
>> 3. Load netconsole and send messages via bond0
>> 4. Remove eth0 from bond0
>> 5. Remove bonding module
>> 6. Remove netconsole module
> 
> Thanks for sending your configuration.
> 
> What values are in /proc/sys/kernel/printk?
> 

I use default values on RHEL5:

6 4 1 7

I don't think this is related with loglevel, what I checked
is dmesg, not just the console screen.

Thanks.
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