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    SubjectRe: [RFC 0/5] kernel: backtrace unwind support
    Em Fri, Feb 10, 2012 at 10:59:51AM -0800, Linus Torvalds escreveu:
    > On Fri, Feb 10, 2012 at 9:43 AM, Peter Zijlstra <> wrote:
    > >
    > > So I CC'ed Linus who has a strong here, jejb since he's the one that
    > > told me several time there's a number of literate dwarfs already in the
    > > kernel and Jan because I think it was him that tried last on x86.
    > I never *ever* want to see this code ever again.
    > Sorry, but last time was too f*cking painful. The whole (and *only*)
    > point of unwinders is to make debugging easy when a bug occurs. But
    > the f*cking dwarf unwinder had bugs itself, or our dwarf information
    > had bugs, and in either case it actually turned several "trivial" bugs
    > into a total undebuggable hell.
    > It was made doubly painful by the developers involved then several
    > times ignoring the problem, and claiming the code was bug-free when it
    > clearly wasn't, or trying to claim that the problem was that we set up
    > some random dwarf information wrong, when THAT GOES WITHOUT SAYING
    > (since dwarf is a complex mess that never gets any actual testing
    > except when things go wrong - at which point the code had better work
    > regardless of whether the dwarf info was correct or not).
    > So no. An unwinder that is several hundred lines long is simply not
    > even *remotely* interesting to me.
    > If you can mathematically prove that the unwinder is correct - even in
    > the presence of bogus and actively incorrect unwinding information -
    > and never ever follows a bad pointer, I'll reconsider.
    > In the absence of that, just follow the damn chain on the stack
    > *without* the "smarts" of an inevitably buggy piece of crap.

    "Vote for --fno-omit-frame-pointer! One register is a cheap price to pay
    for not going insane!"

    /me goes back to non political things.

    - Arnaldo

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