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"Steven N. Severinghaus" 11-06-2009 03:53 PM

Tracking down a fixed bug: 10h38m problem
 
[Resending to bypass moderation queue. -Steve]

Hi, all. I'm trying to track down something that is causing problems in
OpenWRT[1] that seems to be fixed with an Ubuntu kernel. In short, our Via
C3 motherboards hang after about 10 hours and 38 minutes (~32870 seconds,
plus or minus a few seconds), and they wake up as if no time has elapsed if
you hit "enter" on the serial console.

I swapped out the OpenWRT kernel for the one from the 9.04 x86 minimal
CD[2], and the problem disappeared. This suggests to me that your team has
possibly fixed this issue, so I'm wondering if it sounds familiar, and if
you might have a patch to point me to.

If not, I'd like to try to understand what the differences are between the
OpenWRT kernel and the Ubuntu kernel. The problem exists even with all of
the OpenWRT patches disabled, so I should be able to somehow bisect the
differences between a vanilla kernel and the minimal Ubuntu kernel and
identify the magic patch. But at over 10 hours for the bug to manifest, I'm
not looking forward to that process.

So, does this ring a bell at all?

Cheers,
-Steve


[1] https://dev.openwrt.org/ticket/6054
[2] https://help.ubuntu.com/community/Installation/MinimalCD


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Andy Whitcroft 11-06-2009 05:14 PM

Tracking down a fixed bug: 10h38m problem
 
On Fri, Nov 06, 2009 at 10:53:02AM -0600, Steven N. Severinghaus wrote:
> [Resending to bypass moderation queue. -Steve]
>
> Hi, all. I'm trying to track down something that is causing problems in
> OpenWRT[1] that seems to be fixed with an Ubuntu kernel. In short, our Via
> C3 motherboards hang after about 10 hours and 38 minutes (~32870 seconds,
> plus or minus a few seconds), and they wake up as if no time has elapsed if
> you hit "enter" on the serial console.
>
> I swapped out the OpenWRT kernel for the one from the 9.04 x86 minimal
> CD[2], and the problem disappeared. This suggests to me that your team has
> possibly fixed this issue, so I'm wondering if it sounds familiar, and if
> you might have a patch to point me to.
>
> If not, I'd like to try to understand what the differences are between the
> OpenWRT kernel and the Ubuntu kernel. The problem exists even with all of
> the OpenWRT patches disabled, so I should be able to somehow bisect the
> differences between a vanilla kernel and the minimal Ubuntu kernel and
> identify the magic patch. But at over 10 hours for the bug to manifest, I'm
> not looking forward to that process.
>
> So, does this ring a bell at all?

I don't recognise the symptoms specifically no. That kernel would have
been 2.6.28 based and we did take a lot of stable updates for that.
My first suggestion would be to try 2.6.28.10 which was the last full
stable we took, and perhaps the latest 2.6.28.x.

-apw

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"Steven N. Severinghaus" 11-09-2009 04:01 PM

Tracking down a fixed bug: 10h38m problem
 
Andy Whitcroft wrote:
> On Fri, Nov 06, 2009 at 10:53:02AM -0600, Steven N. Severinghaus wrote:
>> Hi, all. I'm trying to track down something that is causing problems in
>> OpenWRT[1] that seems to be fixed with an Ubuntu kernel. In short, our Via
>> C3 motherboards hang after about 10 hours and 38 minutes (~32870 seconds,
>> plus or minus a few seconds), and they wake up as if no time has elapsed if
>> you hit "enter" on the serial console.
[...]
> I don't recognise the symptoms specifically no. That kernel would have
> been 2.6.28 based and we did take a lot of stable updates for that.
> My first suggestion would be to try 2.6.28.10 which was the last full
> stable we took, and perhaps the latest 2.6.28.x.

Thanks for the suggestion, Andy. My latest test was to check out the latest
Ubuntu kernel sources from the Karmic branch and compare that to the latest
server-install CD. As I understand, when I git clone
git://k.u.com/ubuntu/ubuntu-karmic.git, that's already got all of the
Ubuntu-specific patches applied, right?

So having built that with the OpenWRT toolchain, using i386_defconfig, the
problem persists, whereas with the same filesystem image, but with the
server-install kernel swapped in, the problem is gone. I think this leaves
me two possibilities, and I'd appreciate any thoughts on them or any
alternatives.

1) There is a difference between ubuntu-karmic.git and whatever ends up on
the server-install CD. How is that kernel built? Is it patched in some way
beyond what's in git? What kernel config is used? Anything special about
the toolchain that builds it?

2) There is a problem with the OpenWRT toolchain. This possibility worries
me because it sounds like it would be very hard to track down. If this is
the problem, then it has persisted across OpenWRT releases and on several
different build platforms.

Any thoughts?

Cheers,
-Steve

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