[PATCH] Fix "value computed is not used" compile warnings with gcc-4.1

Fix gcc4.1 compile warnings "value computed is not used" with
set_current_state() and set_task_state() on i386/SMP and x86-64.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-x86_64/system.h b/include/asm-x86_64/system.h
index a73f0c7..b7f6603 100644
--- a/include/asm-x86_64/system.h
+++ b/include/asm-x86_64/system.h
@@ -327,7 +327,7 @@
 #define wmb()	asm volatile("" ::: "memory")
 #endif
 #define read_barrier_depends()	do {} while(0)
-#define set_mb(var, value) do { xchg(&var, value); } while (0)
+#define set_mb(var, value) do { (void) xchg(&var, value); } while (0)
 #define set_wmb(var, value) do { var = value; wmb(); } while (0)
 
 #define warn_if_not_ulong(x) do { unsigned long foo; (void) (&(x) == &foo); } while (0)