linux-kernel - Re: [cpuops cmpxchg double V1 2/4] x86: this_cpu_cmpxchg

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Message-ID: <4D08FC9A.8040702@zytor.com>
Date:	Wed, 15 Dec 2010 09:36:26 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [cpuops cmpxchg double V1 2/4] x86: this_cpu_cmpxchg_double()
 support

On 12/15/2010 08:20 AM, Christoph Lameter wrote:
> Better comments:
> 
> Subject: Fixup comments for cmpxchg16b_cpuops_emu
> 
> Indicate that the sematics are not fullly atomic but just per cpu atomic.
> 
> Signed-off-by: Christoph Lameter <cl@...ux.com>
> 
> ---
>  arch/x86/lib/cmpxchg16b_emu.S |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> Index: linux-2.6/arch/x86/lib/cmpxchg16b_emu.S
> ===================================================================
> --- linux-2.6.orig/arch/x86/lib/cmpxchg16b_emu.S	2010-12-15 10:18:18.000000000 -0600
> +++ linux-2.6/arch/x86/lib/cmpxchg16b_emu.S	2010-12-15 10:19:11.000000000 -0600
> @@ -30,6 +30,10 @@ CFI_STARTPROC
>  # Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in
>  # al not via the ZF. Caller will access al to get result.
>  #
> +# Note that this is only useful for a cpuops operation. Meaning that we
> +# do *not* have a fully atomic operation but just an operation that is
> +# *atomic* on a single cpu (as provided by the this_cpu_xx class of macros)
> +#
>  cmpxchg16b_cpuops_emu:
>  	pushf
>  	cli
> 

Could we rename it this_cpu_cmpxchg16b_emu or something like that?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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