[arch-general] wchan info in ps

[Xavier]

On Wed, Jan 6, 2010 at 7:04 PM, Dimitrios Apostolou <jimis at gmx.net> wrote:
> On Sat, 14 Nov 2009, Dimitrios Apostolou wrote:
>>
>> Hello list,
>>
>> is anyone actually getting WCHAN information from either ps or top? To try
>> it just use "ps opid,wchan,cmd". I only get dashes, any idea why?
>>
>
> I managed to resolve this issue. Arch builds its kernels (on 32-bit at
> least) without CONFIG_FRAME_POINTER and loses the ability to produce correct
> stacktraces, either with /proc/$PID/wchan or with SysRq-t or with gdb. On
> the other hand it has one more register free so minor optimisations can be
> performed.
>
> Why don't we set CONFIG_FRAME_POINTER=y? WCHAN output is very useful to be
> lost and frankly I don't think performance losses would be perceivable. Last
> but not least I haven't seen this disabled in any other distro.
>
>

Sorry for not answering earlier, but I probably did not have any ideas
when reading your previous answers.

I am on 64-bit and I have the same result here using Arch kernel.
The reason why it worked for me and still works is that I am always
using a custom kernel, I use
http://cgit.freedesktop.org/nouveau/linux-2.6/ to follow nouveau
development. And I have CONFIG_FRAME_POINTER=y because this option is
quite important indeed

<<< If you say Y here the resulting kernel image will be slightly
 larger and slower, but it gives very useful debugging information
 in case of kernel bugs. (precise oopses/stacktraces/warnings) >>>

I definitely want to get precise oopses/stacktraces/warnings so that I
can report them if needed.
Maybe the average arch user also wants to do that, I don't know.
You can do some research to find out what the big distrib are using in
their default kernel (fedora,suse,debian,ubuntu,...) and/or you can
open a bug in Flyspray.