linux-kernel - [PATCH 03/09] atomic.h : i386 type safety fix

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Date:	Thu, 25 Jan 2007 11:15:48 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...l.org>, Andrew Morton <akpm@...l.org>,
	Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Christoph Hellwig <hch@...radead.org>, ltt-dev@...fik.org,
	systemtap@...rces.redhat.com,
	Douglas Niehaus <niehaus@...s.ku.edu>,
	"Martin J. Bligh" <mbligh@...igh.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Mackerras <paulus@...ba.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: [PATCH 03/09] atomic.h : i386 type safety fix

atomic.h : i386 type safety fix

This patch removes an explicit cast to an integer type for the result returned
by cmpxchg. It is not per se a problem on the i386 architecture, because
sizeof(int) == sizeof(long), but whenever this code is cut'n'pasted to a
different architecture (which happened at least for x86_64), it would simply
accept passing an atomic64_t value as parameter to cmpxchg, xchg and
add_unless, having 64 bits inputs casted to 32 bits.

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

--- a/include/asm-i386/atomic.h
+++ b/include/asm-i386/atomic.h
@@ -207,8 +207,9 @@ static __inline__ int atomic_sub_return(int i, atomic_t *v)
 	return atomic_add_return(-i,v);
 }
 
-#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
-#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic_cmpxchg(v, old, new) \
+	((__typeof__((v)->counter))cmpxchg(&((v)->counter), (old), (new)))
+#define atomic_xchg(v, new) (xchg(&((v)->counter), (new)))
 
 /**
  * atomic_add_unless - add unless the number is a given value
@@ -221,7 +222,7 @@ static __inline__ int atomic_sub_return(int i, atomic_t *v)
  */
 #define atomic_add_unless(v, a, u)				\
 ({								\
-	int c, old;						\
+	__typeof__((v)->counter) c, old;			\
 	c = atomic_read(v);					\
 	for (;;) {						\
 		if (unlikely(c == (u)))				\
-
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