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

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Date:   Sun, 4 Sep 2016 22:23:47 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [Patch net-next 2/2] netns: avoid disabling irq for netns id

Le 02/09/2016 à 19:24, Cong Wang a écrit :
> On Fri, Sep 2, 2016 at 9:39 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
>> 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.
> 
> Note, you can rule out most of them by checking GFP_KERNEL,
> which indicates a process context. ;) For GFP_ATOMIC cases,
> I don't see any of them in hardirq context either, but I am definitely
> not familiar with drivers like infiniband.
> 
Yes, I was thinking to that one. But I'm also not familiar with it ;-)