From f4ccf1d6d01abe8a14bcf252ce5721ccec28c4c4 Mon Sep 17 00:00:00 2001
From: nwhitehorn <nwhitehorn@FreeBSD.org>
Date: Sun, 22 Apr 2012 21:11:01 +0000
Subject: Clarify what we are doing in r234583 a little better: eieio and isync
 do not provide general barriers, but only barriers in the context of the
 atomic sequences here. As such, make them private and keep the global *mb()
 routines using a variant of sync.

---
 sys/powerpc/include/atomic.h | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

(limited to 'sys/powerpc/include')

diff --git a/sys/powerpc/include/atomic.h b/sys/powerpc/include/atomic.h
index 5ff64fb..ce347e9 100644
--- a/sys/powerpc/include/atomic.h
+++ b/sys/powerpc/include/atomic.h
@@ -37,13 +37,21 @@
 #endif
 
 /* NOTE: lwsync is equivalent to sync on systems without lwsync */
-#define mb()	__asm __volatile("lwsync" : : : "memory")
+#define mb()		__asm __volatile("lwsync" : : : "memory")
+#define wmb()		__asm __volatile("lwsync" : : : "memory")
+#define rmb()		__asm __volatile("lwsync" : : : "memory")
+
+/*
+ * The __ATOMIC_XMB() macros provide memory barriers only in conjunction
+ * with the atomic lXarx/stXcx. sequences below. See Appendix B.2 of Book II
+ * of the architecture manual.
+ */
 #ifdef __powerpc64__
-#define wmb()	__asm __volatile("lwsync" : : : "memory")
-#define rmb()	__asm __volatile("lwsync" : : : "memory")
+#define __ATOMIC_WMB()	__asm __volatile("lwsync" : : : "memory")
+#define __ATOMIC_RMB()	__asm __volatile("lwsync" : : : "memory")
 #else
-#define wmb()	__asm __volatile("eieio" : : : "memory")
-#define rmb()	__asm __volatile("isync" : : : "memory")
+#define __ATOMIC_WMB()	__asm __volatile("eieio" : : : "memory")
+#define __ATOMIC_RMB()	__asm __volatile("isync" : : : "memory")
 #endif
 
 /*
@@ -97,13 +105,13 @@
     atomic_add_acq_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;						\
 	__atomic_add_##type(p, v, t);				\
-	rmb();							\
+	__ATOMIC_RMB();						\
     }								\
 								\
     static __inline void					\
     atomic_add_rel_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;						\
-	wmb();							\
+	__ATOMIC_WMB();						\
 	__atomic_add_##type(p, v, t);				\
     }								\
     /* _ATOMIC_ADD */
@@ -183,13 +191,13 @@ _ATOMIC_ADD(long)
     atomic_clear_acq_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;						\
 	__atomic_clear_##type(p, v, t);				\
-	rmb();							\
+	__ATOMIC_RMB();						\
     }								\
 								\
     static __inline void					\
     atomic_clear_rel_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;						\
-	wmb();							\
+	__ATOMIC_WMB();						\
 	__atomic_clear_##type(p, v, t);				\
     }								\
     /* _ATOMIC_CLEAR */
@@ -285,13 +293,13 @@ _ATOMIC_CLEAR(long)
     atomic_set_acq_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;						\
 	__atomic_set_##type(p, v, t);				\
-	rmb();							\
+	__ATOMIC_RMB();						\
     }								\
 								\
     static __inline void					\
     atomic_set_rel_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;						\
-	wmb();							\
+	__ATOMIC_WMB();						\
 	__atomic_set_##type(p, v, t);				\
     }								\
     /* _ATOMIC_SET */
@@ -371,13 +379,13 @@ _ATOMIC_SET(long)
     atomic_subtract_acq_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;							\
 	__atomic_subtract_##type(p, v, t);				\
-	rmb();								\
+	__ATOMIC_RMB();							\
     }									\
 									\
     static __inline void						\
     atomic_subtract_rel_##type(volatile u_##type *p, u_##type v) {	\
 	u_##type t;							\
-	wmb();								\
+	__ATOMIC_WMB();							\
 	__atomic_subtract_##type(p, v, t);				\
     }									\
     /* _ATOMIC_SUBTRACT */
@@ -601,7 +609,7 @@ atomic_cmpset_acq_int(volatile u_int *p, u_int cmpval, u_int newval)
 	int retval;
 
 	retval = atomic_cmpset_int(p, cmpval, newval);
-	rmb();
+	__ATOMIC_RMB();
 	return (retval);
 }
 
@@ -618,7 +626,7 @@ atomic_cmpset_acq_long(volatile u_long *p, u_long cmpval, u_long newval)
 	u_long retval;
 
 	retval = atomic_cmpset_long(p, cmpval, newval);
-	rmb();
+	__ATOMIC_RMB();
 	return (retval);
 }
 
-- 
cgit v1.1