lkml.org 
[lkml]   [2006]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108

Alan Cox wrote:
> The gdb debug data lets you find each line and also the variable
> assignments (except when highly optimised in some cases). Try
> breakpointing there with kgdb and using "where"... A kgdb script is the
> wrong way to do instrumentation but it does demonstrate the information
> is already out there, automatically generated and self maintaining.
>
> You do need the gdb -g debug data, but equally if it was static you'd
> need to recompile with the tracepoint because it would be off by
> default, and there is a very small risk in both cases you'll disturb or
> change the code behaviour/flow.
...
> Thats why we have things like systemtap.
>
> All we appear to lack is systemtap ability to parse debug data so it can
> be told "trace on line 9 of sched.c and record rq and next"

Thanks for the explanation. But I submit to you that both explanations
actually highlight the argument I was making earlier with regards to
dynamic tracing (and gdb info in this case) actually require a non-
expert to chase kernel versions and create appropriate appropriate
scripts/config-info for the post-insertion of instrumentation, with
the risks to kernel developers this may have (ex.: bug report to
lkml from user claiming to have discovered problem in subsystem when,
in fact, trace point by external maintainer was ill-chosen.)

Cheers,

Karim
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-09-15 16:49    [W:0.390 / U:0.200 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site