netdev - Re: [Patch net-next 2/2] netns: avoid disabling irq for netns id

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Date:   Fri, 2 Sep 2016 09:39:32 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [Patch net-next 2/2] netns: avoid disabling irq for netns id

On Fri, Sep 2, 2016 at 1:12 AM, Nicolas Dichtel
<nicolas.dichtel@...nd.com> wrote:
> Le 02/09/2016 à 06:53, Cong Wang a écrit :
>> We never read or change netns id in hardirq context,
>> the only place we read netns id in softirq context
>> is in vxlan_xmit(). So, it should be enough to just
>> disable BH.
>
> Are you sure? Did you audit all part of the code?

I did audit all the callers, and I didn't find any of them in IRQ context.

> peernet2id() is called from netlink core system (do_one_broadcast()). Are you
> sure that no driver call this function from an hard irq context?

I audit all callers of netlink_broadcast(), and I don't see any of
them in hardirq context.

>
> I think that NETLINK_LISTEN_ALL_NSID is largely untested, so it will be hard to
> detect a bug introduced in this feature.

This patch passed my netns stress tests, I have LOCKDEP enabled,
and I don't get any warning or crash etc.