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

[Ingo Molnar <mingo@elte.hu>]

* 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