Re: [PATCH] x86: add the debugfs interface for the sysprof tool

[Ingo Molnar <mingo@elte.hu>]

* Pekka Enberg <penberg@cs.helsinki.fi> wrote:

> Hi,
> 
> On Tue, Feb 26, 2008 at 8:27 AM, Pekka Enberg <penberg@cs.helsinki.fi> wrote:
> > >  You could try passing the --callgraph option to opcontrol.
> >
> >  Hmm, perhaps I am missing something but I don't think that does what
> >  sysprof does. At least I can't find where in the oprofile kernel code
> >  does it save the full stack trace for user-space. John?
> 
> Ok, so as pointed out by Nicholas/Andrew, oprofile does indeed do 
> exactly what sysprof does (see 
> arch/x86/oprofile/backtrace.c::backtrace_address, for example). So, 
> Soeren, any other reason we can't use the oprofile kernel module for 
> sysprof?

as i pointed it out earlier in the thread, the oprofile implementation 
seems buggy because when an event comes from NMI context 
__copy_from_user_inatomic() can fault and re-enable NMIs - causing 
possible stack recursion/corruption. Does not look like an easy fix.

	Ingo