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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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