linux-kernel - Re: [PATCH] atomic: fix atomic_long_cmpxchg/xchg for 64 bit architectures

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Message-ID: <20090429124842.GB32163@Krystal>
Date:	Wed, 29 Apr 2009 08:48:42 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] atomic: fix atomic_long_cmpxchg/xchg for 64 bit
	architectures

* Heiko Carstens (heiko.carstens@...ibm.com) wrote:
> From: Heiko Carstens <heiko.carstens@...ibm.com>
> 
> On a linux-next allyesconfig build:
> 
> kernel/trace/ring_buffer.c:1726:
> 	warning: passing argument 1 of 'atomic_cmpxchg' from incompatible pointer type
> linux-next/arch/s390/include/asm/atomic.h:112:
> 	note: expected 'struct atomic_t *' but argument is of type 'struct atomic64_t *'
> 
> atomic_long_cmpxchg and atomic_long_xchg are incorrectly defined for
> 64 bit architectures. They should be mapped to the atomic64_* variants.
> 
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
> ---
>  include/asm-generic/atomic.h |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> Index: linux-next/include/asm-generic/atomic.h
> ===================================================================
> --- linux-next.orig/include/asm-generic/atomic.h
> +++ linux-next/include/asm-generic/atomic.h
> @@ -132,9 +132,9 @@ static inline long atomic_long_add_unles
>  #define atomic_long_inc_not_zero(l) atomic64_inc_not_zero((atomic64_t *)(l))
>  
>  #define atomic_long_cmpxchg(l, old, new) \
> -	(atomic_cmpxchg((atomic64_t *)(l), (old), (new)))
> +	(atomic64_cmpxchg((atomic64_t *)(l), (old), (new)))
>  #define atomic_long_xchg(v, new) \
> -	(atomic_xchg((atomic64_t *)(l), (new)))
> +	(atomic64_xchg((atomic64_t *)(l), (new)))

Other architectures usually define something along the lines of :

include/asm/atomic.h:#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))

This is why they did not care about calling atomic_cmpxchg or
atomic64_cmpxchg.

This fix looks good. Thanks !

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>


>  
>  #else  /*  BITS_PER_LONG == 64  */
>  

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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