netdev - Re: something is wrong in commit 971f10eca1 - tcp: better TCP_SKB

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Message-ID: <CAHA+R7N9rNUH4aytFG3YLt8nzpERqmf34FgaWbe5R7P0AaWuZw@mail.gmail.com>
Date:	Tue, 14 Oct 2014 11:59:25 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Krzysztof Kolasa <kkolasa@...soft.pl>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	netdev <netdev@...r.kernel.org>, edumazet@...il.com,
	David Miller <davem@...emloft.net>
Subject: Re: something is wrong in commit 971f10eca1 - tcp: better TCP_SKB_CB
 layout to reduce cache line misses

On Tue, Oct 14, 2014 at 6:25 AM, Krzysztof Kolasa <kkolasa@...soft.pl> wrote:
> W dniu 14.10.2014 o 02:09, Cong Wang pisze:
>
>> On Mon, Oct 13, 2014 at 4:59 PM, Cong Wang <cwang@...pensource.com> wrote:
>>>
>>> Probably not related with this bug, but with regarding to the
>>> offending commit, what's the point of the memmove() in tcp_v4_rcv()
>>> since ip_rcv() already clears IPCB()?
>>
>> Oh, ip options are actually saved in ip_rcv_finish()... Hmm, looks scary
>> to play with variable-length array with memmove()....
>>
> On my other old laptop with 32bit kernel next and graphics card Intel 945GM
> just after the revert commit working OK,
> before, after login to gnome shell in some seconds decorations disappear
>
> 32 bit Ubuntu 12.04.5 LTS, gnome shell, kernel source next 14-10-2014
>
> Can anyone confirm this ?
>

Sorry, believe it or not, for me it is hard to find a 32bit machine even VM. :)

Could the attached patch by any chance help? I noticed cookie_v4_check()
still uses IPCB() instead of TCPCB() at TCP layer.

Thanks.

View attachment "tcp-cb.diff" of type "text/plain" (3524 bytes)