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

* 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


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