Re: [PATCH 1/2] x86/asm/entry/32: Open-code CLEAR_RREGS. No code changes.

[Ingo Molnar <mingo@kernel.org>]

* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue,  2 Jun 2015 21:04:01 +0200
> Denys Vlasenko <dvlasenk@redhat.com> wrote:
> 
> > This macro is small, has only four callsites, and one of them is slightly 
> > different using a conditional parameter.
> > 
> > A few saved lines aren't worth the resulting obfuscation.
> 
> I'm curious, why? Did someone recommend this change? I don't see it as 
> obfuscation at all.

So here are a few easy questions, I'm wondering how many minutes it takes for you 
to answer them correctly:

 - What does the CLEAR_RREGS name stand for?

 - What is this macro's purpose?

 - In a single case CLEAR_RREGS takes a 'r9' argument:

    arch/x86/ia32/ia32entry.S:	CLEAR_RREGS
    arch/x86/ia32/ia32entry.S:	CLEAR_RREGS
    arch/x86/ia32/ia32entry.S:	CLEAR_RREGS r9
    arch/x86/ia32/ia32entry.S:	CLEAR_RREGS
    arch/x86/ia32/ia32entry.S:	CLEAR_RREGS

   What is the 'r9' argument's purpose and why is activated in the place where
   it's activated?

The CLEAR_RREGS macro has zero comments. If it takes more than a quick glance to 
determine all these three first-order questions from the source code, then it's an 
obvious code cleanliness fail which needs to be improved.

Thanks,

	Ingo