linux-kernel - Re: Make the 32 bit Frame Pointer backtracer fall back to traditional

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Message-ID: <20080111115656.36048134@laptopd505.fenrus.org>
Date:	Fri, 11 Jan 2008 11:56:56 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	akpm@...ux-foundation.org
Subject: Re: Make the 32 bit Frame Pointer backtracer fall back to
 traditional

On Fri, 11 Jan 2008 11:41:40 -0800 (PST)
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> 
> 
> On Thu, 10 Jan 2008, Arjan van de Ven wrote:
> > 
> > What do you think of this approach instead of your proposal?
> 
> Looks ok to me. I get the feeling that we *should* be able to make the
> 
> 	#ifdef CONFIG_FRAME_POINTER
> 	..
> 
> thing be a bit cleaner with this (since you have the
> non-frame-pointer thing inside the loop as well), and use one common
> routine for it all, with just certain helper functions always
> retuning a NULL or something for the non-frame-pointer thing.

ok I'll try that; I'm also trying some other cleanups
(right now we pick "ebp" and the stack pointer at different levels
in the call chain, so it gets a tad messy)

> 
> (I also wonder if we should limit the number of entries we print out. 
> Sometimes the stack frame ends up being so deep that we lose the 
> *important* stuff. I think it might be good idea to have some rule
> like "the first 5 entries go to the screen, the rest will be
> KERN_DEBUG and only go to the logs by default" - so a "dmesg" would
> show it all, but if the machine is hung, the screen won't have been
> scrolled away from all the other things by a long backtrace!)

that's... a ton more tricky, and realistically needs the patch
to make show_stack take a level argument in the first place.
(I have that done, it's just touching like 125+ files, so
I shelved it as "probably not important enough");


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