netdev - Re: [PATCH 5/5] tcp: ipv4 listen state scaled

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Date:	Wed, 27 Oct 2010 20:44:30 +0400
From:	Dmitry Popov <dp@...hloadlab.com>
To:	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] tcp: ipv4 listen state scaled

On Wed, Oct 27, 2010 at 7:04 PM, Alexey Kuznetsov <kuznet@....inr.ac.ru> wrote:
> Hello!
>
> It looks like there is at least one hole here.
>
> You take lock, check syn table and drop lock in tcp_v4_hnd_req().
> Then you immediately enter tcp_v4_conn_request() and grab lock again.
> Oops, in the tiny hole while lock was dropped the request can be already
> created (even funnier, the whole socket can be already created and even accepted).
> So, if you drop lock, you have to restart the whole tcp_v4_rcv_listen()
> (which seems to be impossible without additional tricks)
>
> Alexey
>

Hello, Alexey!

Yes, it may happen, but I don't see any problem. On 2 same SYN-packets
we will add 2 requests to syn table. Yes, it's not so good, but
nothing criminal, no?

Regards,
Dmitry.
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