To: linux-kernel@vger.kernel.org
From: Holger =?iso-8859-1?q?Hoffst=E4tte?= 
	<holger.hoffstaette@googlemail.com>
Subject: Re: 1e918876 breaks r8169 (linux-3.18+)
Date: Sun, 8 Feb 2015 12:18:33 +0000 (UTC)
Message-ID: <pan.2015.02.08.12.18.33@googlemail.com>
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	<20150203104214.GG24751@breakpoint.cc>
	<20150205165607.GB14936@louise.pinerecords.com>
	<20150206140450.GB19900@louise.pinerecords.com>
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On Fri, 06 Feb 2015 15:04:50 +0100, Tomas Szepe wrote:

> Unfortunately, I have to take this back.  I made the conclusion too early.
> The problem appears with this patch applied, too, only perhaps later and
> with a different frequency pattern.

+1 can confirm - I also see the stack trace in question [1] from time to
time, however even under low/moderate load and more or less randomly.
This also used to happen with 3.14.x, so I don't think it has anything
to do woth the BQL patch pe se.

I *think* - and have suspected for some time now - that this is caused by
a change in TSO/GSO or other offload settings, and that some r8169 models
consequently suffer occasional (or in your case frequent) hiccups.
BQL and/or a qdisc doing requeues might just interfer with whatever upsets
the driver or HW.

I used to turn on all possible settings via ethtool, but am now back to
defaults, which disables sg/tso/gso. Exactly which of these settings is the
culprit remains to be seen.

Holger

[1] https://lkml.org/lkml/2014/12/11/65

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