linux-kernel - Re: [PATCH 1/2] i386: mce cleanup part1: functional change

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Message-ID: <20071009165407.GD13205@amd.com>
Date:	Tue, 9 Oct 2007 18:54:07 +0200
From:	"Joerg Roedel" <joerg.roedel@....com>
To:	"Oleg Verych" <olecom@...wer.upol.cz>
cc:	"Andi Kleen" <andi@...stfloor.org>,
	"Christoph Egger" <Christoph.Egger@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] i386: mce cleanup part1: functional change

On Tue, Oct 09, 2007 at 06:32:30PM +0200, Oleg Verych wrote:
> On Tue, Oct 09, 2007 at 06:06:05PM +0200, Joerg Roedel wrote:
> > > cpu_has() returns int,
> > > but would it be better to have something like
> > > 
> > >   	if (!mce_disabled &&
> > > 	    !(c->x86_capability & (X86_FEATURE_MCA | X86_FEATURE_MCE)) {
> > > 		printk(KERN_INFO "CPU%i: No machine check support available\n",
> > > 			smp_processor_id());
> > 
> > This looks complicated and is harder to read. Its exactly the purpose of the
> > cpu_has() macro to avoid such constructs.
> 
> It is done via test_bit(), which is designed for IO access with all that
> `const volatile' stuff, 2 x unnecessary, can't be optimized here (IMHO).

This code runs only on bootup and once per cpu. I think readable code
is more important here than make it a few cycles faster.

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