netdev - Re: [PATCH v2 4/5] ipvlan: protect addresses with internal spinlock

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Date:	Fri, 10 Jul 2015 15:08:39 +0300
From:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:	Mahesh Bandewar <maheshb@...gle.com>
CC:	linux-netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jiri Benc <jbenc@...hat.com>
Subject: Re: [PATCH v2 4/5] ipvlan: protect addresses with internal spinlock

On 08.07.2015 07:05, Mahesh Bandewar wrote:
> On Fri, Jul 3, 2015 at 5:58 AM, Konstantin Khlebnikov
> <khlebnikov@...dex-team.ru> wrote:
>> Inet6addr notifier is atomic and runs in bh context without RTNL when
>> ipv6 receives router advertisement packet and performs autoconfiguration.
>>
>> This patch adds ipvl_port->addr_lock and helpers: ipvlan_addr_lock_bh,
>> ipvlan_addr_unlock_bh for protecting ipvlan addresses and hash table.
>>
> Frankly I'm not comfortable adding spin-locks all over. I think any
> config that mostly takes place with RTNL makes sense but this
> inet6addr needs to be thought through and implanting spin-locks in
> IPvlan is a work-around for a problem some where else.
> Why can't a work-queue that takes RTNL to call inet6addr-notifier be
> implemented when called from bh?

We already have that work: ipv6 DAD. In v1 patchset was a patch
which moves inet6addr-notifier into it and makes it blockable:

http://www.spinics.net/lists/netdev/msg329017.html

But David Miller objected.

I'm ok with any solution: when spinlock nests inside locked RTNL it
never spins in most cases.

>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
>> ---
>>   drivers/net/ipvlan/ipvlan.h      |   11 +++++++++++
>>   drivers/net/ipvlan/ipvlan_core.c |    2 --
>>   drivers/net/ipvlan/ipvlan_main.c |   33 ++++++++++++++++++++++++++++++---
>>   3 files changed, 41 insertions(+), 5 deletions(-)
>>
> [snip]
>


-- 
Konstantin
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