lwsync is the recommended method of store/store ordering on caching enabled
memory. For those subarchs which have lwsync, use it rather than eieio for
smp_wmb.
Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
---
Index: linux-2.6/include/asm-powerpc/system.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/system.h
+++ linux-2.6/include/asm-powerpc/system.h
@@ -30,8 +30,8 @@
*
* For wmb(), we use sync since wmb is used in drivers to order
* stores to system memory with respect to writes to the device.
- * However, smp_wmb() can be a lighter-weight eieio barrier on
- * SMP since it is only used to order updates to system memory.
+ * However, smp_wmb() can be a lighter-weight lwsync or eieio barrier
+ * on SMP since it is only used to order updates to system memory.
*/
#define mb() __asm__ __volatile__ ("sync" : : : "memory")
#define rmb() __asm__ __volatile__ ("sync" : : : "memory")
@@ -43,9 +43,16 @@
#ifdef __KERNEL__
#define AT_VECTOR_SIZE_ARCH 6 /* entries in ARCH_DLINFO */
#ifdef CONFIG_SMP
+
+#ifdef __SUBARCH_HAS_LWSYNC
+# define SMPWMB lwsync
+#else
+# define SMPWMB eieio
+#endif
+
#define smp_mb() mb()
#define smp_rmb() rmb()
-#define smp_wmb() eieio()
+#define smp_wmb() __asm__ __volatile__ (__stringify(SMPWMB) : : :"memory")
#define smp_read_barrier_depends() read_barrier_depends()
#else
#define smp_mb() barrier()
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