linux-kernel - Re: [PATCHv2 2/3] x86, ptdump: Simplify page flag evaluation code

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Message-ID: <20140924074555.GA3797@gmail.com>
Date:	Wed, 24 Sep 2014 09:45:55 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Mathias Krause <minipli@...glemail.com>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	x86-ml <x86@...nel.org>
Subject: Re: [PATCHv2 2/3] x86, ptdump: Simplify page flag evaluation code


* Mathias Krause <minipli@...glemail.com> wrote:

> On 21 September 2014 21:49, Arjan van de Ven <arjan@...ux.intel.com> wrote:
> > On 9/21/2014 8:26 AM, Mathias Krause wrote:
> >>
> >> -               if (pr & _PAGE_PCD)
> >> -                       pt_dump_cont_printf(m, dmsg, "PCD ");
> >> -               else
> >> -                       pt_dump_cont_printf(m, dmsg, "    ");
> >> +               pt_dump_cont(m, dmsg, "%-4s", pr & _PAGE_USER ? "USR" :
> >> "");
> >
> >
> > while you have some nice cleanups in your patch, I can't say I consider this
> > an improvement.
> > Yes the C standard allows ? to be used like this
> > but no, I don't think it improves readability in general.
> 
> Not in general, but in this case, it does, IMHO.
> 
> > (I think for me the main exception is NULL pointer cases, but this is not
> > one of these)
> 
> Apparently such a pattern (using the question mark operator combined
> with a bit test to choose string constants) is used quite often in the
> linux kernel as a simple grep tells me (probably catches a few false
> positives but still a representative number):

Both can be used (although I too find the original version easier 
to read), and it's usually the taste/opinion of the original 
author whose choice we prefer.

Thanks,

	Ingo
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