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Message-ID: <18907.14029.301492.493938@cargo.ozlabs.ibm.com>
Date: Tue, 7 Apr 2009 21:19:41 +1000
From: Paul Mackerras <paulus@samba.org>
To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
       a.p.zijlstra@chello.nl, tglx@linutronix.de, mingo@elte.hu
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perfcounters/core] x86, perfcounters: add atomic64_xchg()
In-Reply-To: <tip-b226fa12991d6ee9b6b13a7e1de88ec5d25f5007@git.kernel.org>
References: <20090406094518.445450972@chello.nl>
	<tip-b226fa12991d6ee9b6b13a7e1de88ec5d25f5007@git.kernel.org>
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Ingo Molnar writes:

> Complete atomic64_t support on the 32-bit side by adding atomic64_xch().
> 
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> LKML-Reference: <20090406094518.445450972@chello.nl>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> 
> 
> ---
>  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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