Re: BUG-lockdep and freeze (was: Arrr! Linux 2.6.18)

From: Linus Torvalds
Date: Sat Sep 30 2006 - 16:49:49 EST

On Sat, 30 Sep 2006, Andi Kleen wrote:
> We didn't so far find any bug in the unwinder code itself (ok if you don't
> count the performance issue Ingo found) just lots in the annotations and one
> bug in the dwarf2 standard.

I don't think it matters if it's a bug in the unwinding code or in the
data generated for it. It's still a bug in the unwinder.

Those bugs have been compiler bugs, manual annotation bugs, and it
doesn't _matter_ what kind of bugs. The end result is the same: the
unwinder is buggy.

> If you kick the people who add more than three levels of callback
> to core driver code to get their acts together too that's fine
> to me. Unfortunately I don't think that's realistic. So we clearly
> need better unwinding.

I dispute the "clearly". We didn't have _that_ many problems with just
manually filtering out obvious left-overs from some previous callchain.

I mean, really: Andi, point me to anything that was a real problem when we
had no unwinder at all?

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