avoid unnecessary xchg() use in set_mb()
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
#define mb() barrier()
#define rmb() barrier()
#define wmb() barrier()
#define mb() barrier()
#define rmb() barrier()
#define wmb() barrier()
-#define read_barrier_depends() do { } while(0)
-#define set_mb(var, value) do { xchg(&var, value); } while (0)
+#define read_barrier_depends() ((void)0)
+#define set_mb(var, value) ({ (var) = (value); wmb(); })
#define smp_mb() barrier()
#define smp_rmb() barrier()
#define smp_wmb() barrier()
#define smp_mb() barrier()
#define smp_rmb() barrier()
#define smp_wmb() barrier()
-#define smp_read_barrier_depends() do { } while(0)
+#define smp_read_barrier_depends() ((void)0)
#define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
#define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))