As Segher pointed out, inline asm is better than the volatile casting all over
the place. From the PowerPC patch description:
 Also use inline functions instead of macros; this actually
 improves code generation (some code becomes a little smaller,
 probably because of improved alias information -- just a few
 hundred bytes total on a default kernel build, nothing shocking).

My config with march=pentium-m and gcc (GCC) 4.1.2 (Gentoo 4.1.2):
  text    data     bss     dec     hex filename
3434150  249176  176128 3859454  3ae3fe atomic_normal/vmlinux
3435308  249176  176128 3860612  3ae884 atomic_inlineasm/vmlinux
3436201  249176  176128 3861505  3aec01 atomic_inline_volatile/vmlinux
3436203  249176  176128 3861507  3aec03 atomic_volatile/vmlinux

Signed-off-by: Sebastian Siewior <sebastian@breakpoint.cc>
--- a/include/asm-i386/atomic.h
+++ b/include/asm-i386/atomic.h
@@ -22,19 +22,34 @@ typedef struct { int counter; } atomic_t
 /**
  * atomic_read - read atomic variable
  * @v: pointer of type atomic_t
- * 
+ *
  * Atomically reads the value of @v.
- */ 
-#define atomic_read(v)		((v)->counter)
+ */
+static __inline__ int atomic_read(const atomic_t *v)
+{
+	int t;
+
+	__asm__ __volatile__(
+			"movl %1,%0"
+			: "=r"(t)
+			: "m"(v->counter));
+	return t;
+}
 
 /**
  * atomic_set - set atomic variable
  * @v: pointer of type atomic_t
  * @i: required value
- * 
+ *
  * Atomically sets the value of @v to @i.
- */ 
-#define atomic_set(v,i)		(((v)->counter) = (i))
+ */
+static __inline__ void atomic_set(atomic_t *v, int i)
+{
+	__asm__ __volatile__(
+			"movl %1,%0"
+			: "=m"(v->counter)
+			: "ir"(i));
+}
 
 /**
  * atomic_add - add integer to atomic variable

-- 

-
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