[lttng-dev] Extract lttng trace from kernel coredump

[Mathieu Desnoyers]

----- Original Message -----
> From: "Corey Minyard" <minyard at acm.org>
> To: "David Goulet" <dgoulet at efficios.com>
> Cc: lttng-dev at lists.lttng.org
> Sent: Tuesday, January 14, 2014 3:39:43 PM
> Subject: Re: [lttng-dev] Extract lttng trace from kernel coredump
> 
> On 01/14/2014 12:42 PM, David Goulet wrote:
> > On 13 Jan (16:39:47), Corey Minyard wrote:
> >> I'm working on a feature to allow an lttng trace to be extracted from a
> >> kernel coredump, and I'm wondering the best way to proceed.  I've looked
> >> at extracting from the existing data structures, but that would require
> >> something to always have a trace file open and it looks more than a
> >> little complicated.  I was thinking instead of having a different trace
> >> channel for configuring this coredump and some globals to point to the
> >> various data structures.  Would that be the best way to pursue this?  Is
> >> there a better way, perhaps?
> > Oh yes we do actually already have a way to do that :)
> >
> > Please see:
> > https://git.lttng.org/?p=lttng-tools.git;a=tree;f=extras/core-handler;h=29ded89a71fd36e159d671ca1f405cea394f8683;hb=HEAD
> >
> > With the snapshot feature, it's quite easy to do that. Hope that helps
> > you with what you are trying to achieve.
> 
> I did see that, but it seems to be for an application coredump.  I was
> looking for something that would work for a kernel coredump.  So that if
> the kernel crashes, you can use kdump to extract the kernel core and
> then extract the LTT buffers from that.  The idea is that if the kernel
> crashes, you can get some idea of what was happening before the crash.

Something along these lines have been proposed a while back on the ML,
but it was against an old LTTng version (0.x):

http://lists.lttng.org/pipermail/lttng-dev/2010-August/014239.html

It might be interesting to adapt it to the newer LTTng 2.x. Anyone interested
to look into this ?

Thanks,

Mathieu

> 
> 
> Thanks,
> 
> -corey
> 
> > Cheers!
> > David
> >
> >> Thanks,
> >>
> >> -corey
> >>
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> >> lttng-dev at lists.lttng.org
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> 
> 
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com