linux-kernel - Re: [PATCH 2/3] x86, cpu: Clean up and unify the NOP selection infrastructure

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Message-ID: <1303171116.7181.91.camel@gandalf.stny.rr.com>
Date:	Mon, 18 Apr 2011 19:58:35 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, Jason Baron <jbaron@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>, tglx@...utronix.de,
	mingo@...e.hu, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/3] x86, cpu: Clean up and unify the NOP selection
 infrastructure

On Mon, 2011-04-18 at 16:39 -0700, H. Peter Anvin wrote:
> On 04/18/2011 04:31 PM, Steven Rostedt wrote:
> > 
> > Can we please add a comment to this. The original (above) was confusing
> > enough, but at least it used asm() so it wasn't that bad to figure out.
> > Or at least the asm() usage would trigger in one's mind to think "Damn!
> > They chose to use 'asm', it must be some kind of nasty trick. Let's take
> > a better look at WTF they are doing!".
> > 
> > Now the use a normal character array actual makes this even more subtle.
> 
> OK... I never thought it was particularly subtle, but okay.

It took me 2 minutes to figure out what it was doing, but then maybe I'm
slow ;) But having a comment may save a minute or two of frustration
from other reviewers as well.

> 
> A much bigger issue with this particular patch is that the
> __init{data,const}_or_module presumably needs to be removed from these
> structures, right?

Ah, as you have this:


> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -260,9 +260,9 @@ do_ftrace_mod_code(unsigned long ip, void
> *new_code)
>         return mod_code_status;
>  }
>  
> -static unsigned char *ftrace_nop_replace(void)
> +static const unsigned char *ftrace_nop_replace(void)
>  {
> -       return ideal_nop5;
> +       return ideal_nops[NOP_ATOMIC5];
>  }
> 
I would say, yes get rid of the init annotations.

-- Steve


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