netdev - Re: [PATCH net-next v5 0/11] bonding: rebuild the lock use for bond monitor

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Date:	Sat, 14 Dec 2013 18:02:25 +0800
From:	Ding Tianhong <dthxman@...il.com>
To:	David Miller <davem@...emloft.net>, dingtianhong@...wei.com
CC:	fubar@...ibm.com, andy@...yhouse.net, nikolay@...hat.com,
	vfalico@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 0/11] bonding: rebuild the lock use for bond
 monitor

于 2013/12/14 15:01, David Miller 写道:
> From: Ding Tianhong <dingtianhong@...wei.com>
> Date: Wed, 11 Dec 2013 12:59:52 +0800
> 
>> Now the bond slave list is not protected by bond lock, only by RTNL,
>> but the monitor still use the bond lock to protect the slave list,
>> it is useless, according to the Veaceslav's opinion, there were
>> three way to fix the protect problem:
>>
>> 1. add bond_master_upper_dev_link() and bond_upper_dev_unlink()
>>    in bond->lock, but it is unsafe to call call_netdevice_notifiers()
>>    in write lock.
>> 2. remove unused bond->lock for monitor function, only use the exist
>>    rtnl lock(), it will take performance loss in fast path.
>> 3. use RCU to protect the slave list, of course, performance is better,
>>    but in slow path, it is ignored.
>>
>> obviously the solution 1 is not fit here, I will consider the 2 and 3
>> solution. My principle is simple, if in fast path, RCU is better,
>> otherwise in slow path, both is well, but according to the Jay Vosburgh's
>> opinion, the monitor will loss performace if use RTNL to protect the all
>> slave list, so remove the bond lock and replace with RCU.
>>
>> The second problem is the curr_slave_lock for bond, it is too old and
>> unwanted in many place, because the curr_active_slave would only be
>> changed in 3 place:
>>
>> 1. enslave slave.
>> 2. release slave.
>> 3. change active slave.
>>
>> all above were already holding bond lock, RTNL and curr_slave_lock
>> together, it is tedious and no need to add so mach lock, when change
>> the curr_active_slave, you have to hold the RTNL and curr_slave_lock
>> together, and when you read the curr_active_slave, RTNL or curr_slave_lock,
>> any one of them is no problem.
>>
>> for the stability, I did not change the logic for the monitor,
>> all change is clear and simple, I have test the patch set for lockdep,
>> it work well and stability.
> 
> Series applied, thanks.
> --

Hi David:

The last version of the patchset is v6, and the v6 is a little different from v5,
I think you have missed the last version, and found you applied the v5 patchset.

Regards
Ding

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