[Cbe-oss-dev] Re Refactored cell powerpc oprofile patch

[Carl Love]

Denis:

Can you give an overview of what the ps3-lpm module does?  What happens
when ps3-lpm.c is remmodded?  I guess I need to understand what the
module does so I can figure out what impact it has on OProfile.  I
understand the processor architecture but I am not at all familiar with
the PS3 system as a whole.

           Carl Love



On Wed, 2008-03-05 at 10:57 +0100, Denis Joseph Barrow wrote:
> >You made the comment  "When ps3-lpm.c is insmodded it needs to restart 
> the call the >generic code to restart oprofile as some stuff".  I don't 
> follow this.
> 
> The ps3-lpm.ko driver can be inserted & removed in spite of oprofile
> actually using it. i.e. if ps3-lpm.ko is remmodded while oprofile
> is using it oprofile must be stopped as the pmu_ops now point to 
> functions which were in ps3-lpm.ko & will crash the kernel.
> I was thinking about this yesterday & it probably would be nicer to
> have a set of pmu_ops which point to functions which do nothing.
> This however makes the patch bigger as I'd have 20 or 30 functions
> for the pmu_ops which actually do nothing.
> 
> oprofile has no dependancies on ps3-lpm.ko.
> This means that I need to reregister ps3-lpm.ko with oprofile if it
> is inserted late. It is however inserted by default by udev
> but it can be rmmoded as so symbol in oprofile depends on it being
> loaded.
> 
> If ps3-lpm.ko is always around I don't see any advantage in making
> it a module except that it will only be loaded if the kernel
> is actually running on a ps3.
> If the module is always loaded before oprofile which it is at the moment
> & is gauranteed  to stay loaded I can remove my re registeration rubbish 
> ( probably
> around 200 lines of bad code).
> Will I force the module ps3-lpm.ko use count to 1 if it is a ps3 & is 
> probed Geoff ?
> so it can't be unloaded if oprofile is put running?
> How do I detect if oprofile is running?
>