Re: [PATCH] uprobes: Cleanup !CONFIG_UPROBES decls, unexportxol_area
From: Oleg Nesterov
Date: Mon Nov 11 2013 - 14:57:29 EST
On 11/11, Ingo Molnar wrote:
>
> * Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> > +++ b/kernel/events/uprobes.c
> > @@ -86,6 +86,25 @@ struct return_instance {
> > };
> >
> > /*
> > + * On a breakpoint hit, thread contests for a slot. It frees the
> > + * slot after singlestep. Currently a fixed number of slots are
> > + * allocated.
> > + */
> > +struct xol_area {
>
> So, my main complaint about the uprobes code isn't functional but
> documentational, similar to what I outlined a few days ago: what this
> comment does not explain is exactly what a 'XOL area' is.
>
> You guys are changing code that reads like gobbledygook to people reading
> it for the first time.
Not that I am trying to defense uprobes, but this is equally true for
any piece of kernel code, at least to me ;)
> It's understandable that you want to use
> abbreviations and I don't object against that, but please explain key
> concepts and data structures when they first come up
Well, this patch only move the definition with the comments, but:
> - a very good place
> to do that is in places where key structures are declared.
>
> I didn't find any high level description of the XOL code, one which makes
> clear that how we manage these out of line execution areas:
I have to agree, all these comments do not really help...
> The one that comes closest is:
>
> * This area will be used for storing instructions for execution out of line.
>
> ... but that is a single sentence and deep inside the XOL code already.
and even this comment should be probably moved up to the "struct xol_area",
> Really, please make a better job of introducing other kernel hackers to
> the code you are writing ...
>
> Maybe even split the XOL code out into kernel/events/uprobes_xol.c or so?
I do not really think a separate uprobes_xol.c makes sense. I think it would
be nice to have the high-level "uprobes design" doc in uprobetracer.txt, or
> That will give a natural place to explain yourselves at the beginning of
> the file.
or even in the beginning of uprobes.c, I agree.
Don't get me wrong, I am not volunteering ;) But at least I'll try to
pay more attention to the comments when I change the code next time.
Oleg.
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