Re: [PATCH] percpu: fix generic definition of __this_cpu_add_and_return()
From: Torsten Kaiser
Date: Fri Feb 24 2012 - 10:33:49 EST
On Sun, Feb 19, 2012 at 3:29 PM, Konstantin Khlebnikov
<khlebnikov@xxxxxxxxxx> wrote:
> This patch adds missed "__" into function prefix.
> Otherwise on all archectures (except x86) it expands to irq/preemtion-safe
> variant: _this_cpu_generic_add_return(), which do extra irq-save/irq-restore.
> Optimal generic implementation is __this_cpu_generic_add_return().
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
> ---
> include/linux/percpu.h | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> index 32cd1f6..3b609eb 100644
> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -718,7 +718,8 @@ do { \
> # ifndef __this_cpu_add_return_8
> # define __this_cpu_add_return_8(pcp, val) __this_cpu_generic_add_return(pcp, val)
> # endif
> -# define __this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val)
> +# define __this_cpu_add_return(pcp, val) \
> + __pcpu_size_call_return2(__this_cpu_add_return_, pcp, val)
> #endif
>
> #define __this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(val))
I think, the same fix should be applied to the lines following this patch:
#define __this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(val))
#define __this_cpu_inc_return(pcp) this_cpu_add_return(pcp, 1)
#define __this_cpu_dec_return(pcp) this_cpu_add_return(pcp, -1)
Shouldn't these other operations also only give the __ relaxed guarantees?
HTH
Torsten
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