netdev - Re: netlink_carrier_on() race condition?

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Date:	Mon, 15 Nov 2010 02:15:12 +0200
From:	Eliad Peller <eliad@...ery.com>
To:	netdev@...r.kernel.org
Cc:	Jamal Hadi Salim <hadi@...erus.ca>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: netlink_carrier_on() race condition?

hi,

i'm still waiting for some response regarding this issue.
i've encountered this concrete issue, and i want to make sure i fully
understand the situation before submitting some redundant patch.

thanks,
Eliad.

On Thu, Nov 4, 2010 at 9:43 PM, Eliad Peller <eliad@...ery.com> wrote:
> hi,
>
> i might be missing something, but i think there is some race condition
> in netlink_carrier_on():
> when calling it, it clears the __LINK_STATE_NOCARRIER flag and
> enqueues a work to do everything needed.
> this cause a period, in which  __LINK_STATE_NOCARRIER is unset (which
> implies IFF_LOWER_UP), but the default qdiscs are not attached yet
> (since the work hasn't been executed yet).
> userspace might get some netlink events (e.g. wireless wext) in which
> the IFF_LOWER_UP flag is set, but the queues are not ready.
>
> shouldn't we clear the flag only after all the work is done?
>
> thanks,
> Eliad.
>
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