x86: fix IO write barrier

wmb() on x86 must always include a barrier, because stores can go out of
order in many cases when dealing with devices (eg. WC memory).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 5 deletions

diff --git a/include/asm-x86/system_64.h b/include/asm-x86/system_64.h
index 02175aa1d16a..eff730b11926 100644
--- a/include/asm-x86/system_64.h
+++ b/include/asm-x86/system_64.h
@@ -159,12 +159,8 @@ static inline void write_cr8(unsigned long val)
  */
 #define mb()    asm volatile("mfence":::"memory")
 #define rmb()   asm volatile("lfence":::"memory")
-
-#ifdef CONFIG_UNORDERED_IO
 #define wmb()   asm volatile("sfence" ::: "memory")
-#else
-#define wmb()   asm volatile("" ::: "memory")
-#endif
+
 #define read_barrier_depends()  do {} while(0)
 #define set_mb(var, value) do { (void) xchg(&var, value); } while (0)