Re: Intel Memory Ordering White Paper

[Nick Piggin]

On Saturday 08 September 2007 08:26, Jesse Barnes wrote:
> FYI, we just released a new white paper describing memory ordering for
> Intel processors:
> http://developer.intel.com/products/processor/manuals/index.htm
>
> Should help answer some questions about some of the ordering primitives
> we use on i386 and x86_64.

So, can we finally noop smp_rmb and smp_wmb on x86?
Index: linux-2.6/include/asm-i386/system.h
===================================================================
--- linux-2.6.orig/include/asm-i386/system.h
+++ linux-2.6/include/asm-i386/system.h
@@ -286,7 +286,7 @@ static inline unsigned long get_limit(un
 
 #ifdef CONFIG_SMP
 #define smp_mb()	mb()
-#define smp_rmb()	rmb()
+#define smp_rmb()	barrier()
 #define smp_wmb()	wmb()
 #define smp_read_barrier_depends()	read_barrier_depends()
 #define set_mb(var, value) do { (void) xchg(&var, value); } while (0)
Index: linux-2.6/include/asm-x86_64/system.h
===================================================================
--- linux-2.6.orig/include/asm-x86_64/system.h
+++ linux-2.6/include/asm-x86_64/system.h
@@ -141,8 +141,8 @@ static inline void write_cr8(unsigned lo
 
 #ifdef CONFIG_SMP
 #define smp_mb()	mb()
-#define smp_rmb()	rmb()
-#define smp_wmb()	wmb()
+#define smp_rmb()	barrier()
+#define smp_wmb()	barrier()
 #define smp_read_barrier_depends()	do {} while(0)
 #else
 #define smp_mb()	barrier()