Re: [cpuops cmpxchg double V1 2/4] x86: this_cpu_cmpxchg_double()support
From: H. Peter Anvin
Date: Wed Dec 15 2010 - 12:37:28 EST
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@xxxxxxxxx>
>
> ---
> 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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