Subject: Re: [PATCH 1/1] bond: relocate rcu_read_lock and rcu_read_unlock

From: Nikolay Aleksandrov <[email-masked]>
Date: Mon, 1 Feb 2016 12:08:05 +0100

On 02/01/2016 12:01 PM, Nikolay Aleksandrov wrote:
> On 02/01/2016 04:31 AM, [email-masked] wrote:
>> From: Zhu Yanjun <[email-masked]>
>>
>> rcu_read_lock and rcu_read_unlock are to protect the function
>> bond_miimon_inspect. As such, moving rcu_read_lock and rcu_read_unlock
>> to the function bond_miimon_inspect to make the source code compact.
>>
>> CC: Jay Vosburgh <[email-masked]>
>> CC: Veaceslav Falico <[email-masked]>
>> CC: Andy Gospodarek <[email-masked]>
>> Signed-off-by: Zhu Yanjun <[email-masked]>
>> ---
>>  drivers/net/bonding/bond_main.c | 9 ++++-----
>>  1 file changed, 4 insertions(+), 5 deletions(-)
>>
> 
> Not true, RCU also protects the slave dereference in bond_should_notify_peers().
> Even though there's already a rcu_read_lock() while doing the dereference
> itself, it is there only to please RCU, IIRC. The only "simplification" you

Err, I meant to please lockdep when being called with RTNL.

> can do is remove the rcu_read_lock/unlock() around the slave deref in
> bond_should_notify_peers and use rcu_dereference_rtnl() as it can be used either
> in RCU protected region or with RTNL held. Also I think net-next is still
> closed (and that's where this should be targeted at).
> 
> Cheers,
>  Nik
> 
>