Re: [tip:perfcounters/core] x86, perfcounters: add atomic64_xchg()

From: Paul Mackerras
Date: Tue Apr 07 2009 - 07:19:58 EST


Ingo Molnar writes:

> Complete atomic64_t support on the 32-bit side by adding atomic64_xch().
>
> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> LKML-Reference: <20090406094518.445450972@xxxxxxxxx>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
>
>
> ---
> arch/x86/include/asm/atomic_32.h | 6 ++++++
> 1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h
> index 977250e..a9fef6c 100644
> --- a/arch/x86/include/asm/atomic_32.h
> +++ b/arch/x86/include/asm/atomic_32.h
> @@ -306,6 +306,12 @@ static inline void atomic64_set(atomic64_t *ptr, unsigned long long new_val)
> } while (atomic64_cmpxchg(ptr, old_val, new_val) != old_val);
> }
>
> +static inline void
> +atomic64_xchg(atomic64_t *ptr, unsigned long long new_val)
> +{
> + atomic64_set(ptr, new_val);
> +}

Umm, I don't know much about x86, but that doesn't look like an
exchange operation to me... Shouldn't it return a value, for a start?

Paul.
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