linux-kernel - Re: [PATCH] x86: Replace uses of current_cpu_data with this

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Message-ID: <alpine.DEB.2.00.1012080929590.23407@router.home>
Date:	Wed, 8 Dec 2010 09:33:40 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] x86: Replace uses of current_cpu_data with this_cpu
 ops

On Wed, 8 Dec 2010, Eric Dumazet wrote:

> > In the long run, it might be a good idea to remove cpu_data() macro
> > too and use per_cpu macro directly.
> >
>
> or introduce this_cpu_has() to remove the adress computation
>
> -	if (cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_ARAT)) {
>
> +	if (this_cpu_has(X86_FEATURE_ARAT)) {
>

The fundamental problem is that bitops require memory addresses which does
not work with per cpu ops.

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