linux-kernel - Re: [PATCH] atomic_cmpxchg return type error

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Message-ID: <20061130232354.GA12359@muc.de>
Date:	Fri, 1 Dec 2006 00:23:54 +0100
From:	Andi Kleen <ak@....de>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
Cc:	vojtech@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] atomic_cmpxchg return type error

On Thu, Nov 30, 2006 at 04:17:06PM -0500, Mathieu Desnoyers wrote:
> Hi,
> 
> I just noticed that a atomic_cmpxchg, that would be given an atomic64_t
> parameter, would cast the return value as a (int). In the typical use of this
> primitive, the result would be that the 32 MSB would be lost when comparing
> against the original value. It also affects atomic_add_unless. Note that there
> is no atomic64_cmpxchg nor atomic64_add_unless, which might make things a
> little clearer.

Normally you're supposed to only use atomic64_* with atomic64_t

While it works for most by accident on x86 to just use atomic_* 
with atomic64_t it's not portable to other architectures.

If you want to use those with atomic64_t suitable macros would need
to be added on all architectures.

-Andi
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