netdev - Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison overwritten

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Date:	Tue, 5 Jul 2011 07:56:50 +0400
From:	Alexey Zaytsev <alexey.zaytsev@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Michael Büsch <m@...s.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, Gary Zambrano <zambrano@...adcom.com>,
	bugme-daemon@...zilla.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Pekka Pietikainen <pp@...oulu.fi>,
	Florian Schirmer <jolt@...box.org>,
	Felix Fietkau <nbd@...nwrt.org>, Michael Buesch <mb@...sch.de>
Subject: Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison overwritten

On Tue, Jul 5, 2011 at 07:44, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le mardi 05 juillet 2011 à 02:29 +0400, Alexey Zaytsev a écrit :
>> On Tue, Jul 5, 2011 at 00:25, Alexey Zaytsev <alexey.zaytsev@...il.com> wrote:
>> > On Mon, Jul 4, 2011 at 19:12, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> >> Le lundi 04 juillet 2011 à 16:43 +0200, Michael Büsch a écrit :
>> >>> On Mon, 4 Jul 2011 16:27:26 +0200
>> >>> Michael Büsch <m@...s.ch> wrote:
>> >>> > We do this in b43, which has exactly the same DMA engine.
>> >>>
>> >>> (Ok, it turns out we don't do this in b43 (We only do it on the TX side).
>> >>>  But that's a bug. We should do a wmb() on the RX side before advancing the
>> >>>  descriptor ring pointer.)
>> >>
>> >> I am wondering what happens if RX ring is set to 64, and we receive
>> >> exactly 64 buffers in one round, B44_DMARX_PTR wont change at all ?
>> >>
>> >> Alexey, could you try this patch please ?
>> >
>> > Sorry, did not help.
>> >
>>
>> Ran a few rounds of tcpdump. Seeing a significant number or duplicate
>> ACKs from the problematic machine. Not seeing them when testing
>> between this machine and an other linux box. Or the illumos machine
>> and the other linux box.
>>
>> Dumps are available here:
>>
>> http://zaytsev.su/tmp/caps/
>>
>> dump1-3 - between the problematic machine an the illumos box,
>> collected on illumos side. All show dups.
>> dump5 - between an other linux box and the illumos machine, no dups.
>> Collcted on the illumos side.
>> dump-linux - between 2 linux machines, collected on the
>> non-problematic side. No dups, no corruptions.
>>
>> 192.168.0.33 - the problematic machine.
>> 192.168.0.72 - the illumos machine.
>> 192.168.0.122 - an other linux machine.
>
> ??
>
> I dont care about duplicate acks at this point.
>
> Thats a separate issue (TCP layer)
>

Maybe some tx packets are just sent out more then once? Or a single
packet is sent out instead of some other packets?
The delays between two dups is short, and they come in bursts, up to a
few hundreds of duplicate packets at a time.

> Do you still have memory scribbles ?
Yes.

>
> I wonder if the problem is not coming from the "fast recovery" added in
> commit 32737e934a952c (PATCH: b44 Handle RX FIFO overflow better
> (simplified))
>

I've tested back to 2.6.27. I did not test all releases of course, so
maybe this was fixed, and then broken again.
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