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

Ingo Molnar
2006-09-30T20:57:16Z

* Linus Torvalds <torvalds@osdl.org> wrote:

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

personally, i like perfect stacktraces, alot. x86_64 was a huge pain for
me without the unwinder. I got so used to perfect backtraces on i686
(when using %ebp frames) during the years, and i had to look at _many_
backtraces with lockdep. On x86_64 it was just constant brain-drain to
think away bogus stack entries. Yes, i can do it no problem when i have
to look at only a few stacktraces per day, but if it's hundreds per day
it's _alot_ of brainpower wasted.

(i'd have been happy with an %rbp based unwinder for x86_64, in fact i
implemented it for lockdep and used it for some time on x86_64, but Andi
wanted a dwarf-based, lower-overhead one. Andi also nicely integrated it
into stacktrace.c.)

Ingo