linux-kernel - Re: [PATCH 09/21] amd64_edac: assign DRAM chip select base and mask in a family-specific way

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Date:	Wed, 6 May 2009 11:38:59 -0700 (PDT)
From:	Doug Thompson <norsk5@...oo.com>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>
Cc:	Borislav Petkov <borislav.petkov@....com>,
	akpm@...ux-foundation.org, greg@...ah.com, mingo@...e.hu,
	tglx@...utronix.de, hpa@...or.com, dougthompson@...ssion.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/21] amd64_edac: assign DRAM chip select base and mask in a family-specific way


- On Tue, 5/5/09, Mauro Carvalho Chehab <mchehab@...hat.com> wrote:

> From: Mauro Carvalho Chehab <mchehab@...hat.com>
> Subject: Re: [PATCH 09/21] amd64_edac: assign DRAM chip select base and mask in a family-specific way
> To: "Doug Thompson" <norsk5@...oo.com>
> Cc: "Borislav Petkov" <borislav.petkov@....com>, akpm@...ux-foundation.org, greg@...ah.com, mingo@...e.hu, tglx@...utronix.de, hpa@...or.com, dougthompson@...ssion.com, linux-kernel@...r.kernel.org
> Date: Tuesday, May 5, 2009, 3:39 PM
> Em Tue, 5 May 2009 12:28:01 -0700
> (PDT)
> Doug Thompson <norsk5@...oo.com>
> escreveu:

> > BACKGROUND: The error checking of the pci config space
> read was added during the time when the kernel couldn't read
> the extended 4k config space via the AMD IOConfig port
> access function (12 bits of offset) not via MMCONFIG. 
> 
> As this is unlikely to happen, I would also replace the:
>     if (err != 0)
> 
> by:
>     if (unlikely(err))
> 
> in order to optimize the tests a little bit, avoiding the
> risk of cache flushes due to the branches.
> 
> Cheers,
> Mauro
> 

when the driver is configured without DEBUG config flag on, the statement becomes:

    if (exp)
         ;

which with a good optimizer the code disappears altogether in the production condition. Only with DEBUGGING on will these outputs be generated.

thanks for the extra review eyes

doug t

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