Messages in this thread |  | | Date | Fri, 10 Feb 2012 17:27:14 -0200 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [RFC 0/5] kernel: backtrace unwind support |
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Em Fri, Feb 10, 2012 at 10:59:51AM -0800, Linus Torvalds escreveu: > On Fri, Feb 10, 2012 at 9:43 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> 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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