[maemo-developers] Warnings when starting scratchbox (diablo) on debian Lenny

[From: Guillem Jover]

Hi,

On Fri, 2009-03-13 at 15:26:52 +0100, Jeremiah C. Foster wrote:
> When I start up my dev environment in scratchbox I call 'af-sb-init.sh
> start'. I then get this warning;
> 
> Starting Maemo Launcher: maemo-launcher.
> defender: died my parent is not who he claims to be
> maemo-launcher: warning rising the oom shield for pid=8471 status=2816

> I assume this is not so serious since everything works, but I would love
> to know a little more about what is happening here.

Yeah, it should not be a problem under sbox as there should not be
the same memory limitations as on the device.

> And shouldn't that be "raising oom shield" instead of "rising"? :)

Hmm ‘rising’ is not a verb, fixed the typo now in my git tree, thanks!

> Google also mentions the Linux Out of Memory killer which may be why the
> shield is protecting against. Am I right in that assumption?

Right.

Given that the maemo-launcher main process is spawning most of the UI
processes on the device it gets lots of points from the OOM killer,
even if it's not directly at fault for its childs allocations.

So it tries to protect itself from OOM killer by executing the defender
(found in /usr/lib/maemo-launcher/defender). The defender is a suid root
binary that disables the OOM killer for the main maemo-launcher, as
the latter is running with normal user privs. To make sure no other
process can also use the defender, it checks for its caller to be
exactly /usr/bin/maemo-launcher (or whatever path was used as prefix
at configure time).

regards,
guillem