linux-kernel - Re: [BUG] packet loss with PROVE

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Date:	Tue, 22 Mar 2016 06:31:54 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Chris Bainbridge <chris.bainbridge@...il.com>
Cc:	linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	mchehab@...radead.org, markus@...ppelsdorf.de, tony.luck@...el.com
Subject: Re: [BUG] packet loss with PROVE_LOCKING, bisected to EDAC fix

On Mon, Mar 21, 2016 at 09:42:09PM +0000, Chris Bainbridge wrote:
> Hi,
> 
> I was testing something on an old server (Dell T105 opteron) and noticed
> packet loss after updating the kernel from 3.10 to 4.5. The test was:
> 
> On Dell run: iperf -s
> On another system: iperf3 -c dell -u -b 20M -l 1k -t 1000
> 
> This sends a 20mbit UDP stream to the Dell. It works fine normally (0%
> packet loss), but when CONFIG_PROVE_LOCKING is enabled there is high
> (35%) packet loss. (DEBUG_LOCKDEP also seems to cause packet loss)
> 
> The packet loss bisected back to:
> 
> commit 88d84ac97378c2f1d5fec9af1e8b7d9a662d6b00
> Author: Borislav Petkov <bp@...e.de>
> Date:   Fri Jul 19 12:28:25 2013 +0200
> 
>     EDAC: Fix lockdep splat

Hmm, how would that cause a packet loss?!

> I have confirmed that the commit preceding this (v3.11-rc1) is fine and
> that 88d84a introduced the bug.

Did you revert this commit ontop of 4.5 and reproduce again? Do you see
the same packet loss?

What kind of hw is that target system, can you send full dmesg and
.config?

Thanks.

-- 
Regards/Gruss,
    Boris.

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